Update to w3m-0.2.1-inu-1.6.

19 files changed, 3484 insertions, 0 deletions

diff --git a/gc/doc/README b/gc/doc/README
new file mode 100644
index 0000000..c6b48c3
--- /dev/null
+++ b/gc/doc/README
@@ -0,0 +1,617 @@
+Copyright (c) 1988, 1989 Hans-J. Boehm, Alan J. Demers
+Copyright (c) 1991-1996 by Xerox Corporation.  All rights reserved.
+Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
+Copyright (c) 1999-2001 by Hewlett-Packard Company. All rights reserved.
+
+The file linux_threads.c is also
+Copyright (c) 1998 by Fergus Henderson.  All rights reserved.
+
+The files Makefile.am, and configure.in are
+Copyright (c) 2001 by Red Hat Inc. All rights reserved.
+
+The files config.guess and a few others are copyrighted by the Free
+Software Foundation.
+
+THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+
+Permission is hereby granted to use or copy this program
+for any purpose,  provided the above notices are retained on all copies.
+Permission to modify the code and to distribute modified code is granted,
+provided the above notices are retained, and a notice that the code was
+modified is included with the above copyright notice.
+
+A few of the files needed to use the GNU-style build procedure come with
+slightly different licenses, though they are all similar in spirit.  A few
+are GPL'ed, but with an exception that should cover all uses in the
+collector.  (If you are concerned about such things, I recommend you look
+at the notice in config.guess or ltmain.sh.)
+
+This is version 6.0 of a conservative garbage collector for C and C++.
+
+You might find a more recent version of this at
+
+http://www.hpl.hp.com/personal/Hans_Boehm/gc
+
+OVERVIEW
+
+    This is intended to be a general purpose, garbage collecting storage
+allocator.  The algorithms used are described in:
+
+Boehm, H., and M. Weiser, "Garbage Collection in an Uncooperative Environment",
+Software Practice & Experience, September 1988, pp. 807-820.
+
+Boehm, H., A. Demers, and S. Shenker, "Mostly Parallel Garbage Collection",
+Proceedings of the ACM SIGPLAN '91 Conference on Programming Language Design
+and Implementation, SIGPLAN Notices 26, 6 (June 1991), pp. 157-164.
+
+Boehm, H., "Space Efficient Conservative Garbage Collection", Proceedings
+of the ACM SIGPLAN '91 Conference on Programming Language Design and
+Implementation, SIGPLAN Notices 28, 6 (June 1993), pp. 197-206.
+
+Boehm H., "Reducing Garbage Collector Cache Misses", Proceedings of the
+2000 International Symposium on Memory Management.
+
+  Possible interactions between the collector and optimizing compilers are
+discussed in
+
+Boehm, H., and D. Chase, "A Proposal for GC-safe C Compilation",
+The Journal of C Language Translation 4, 2 (December 1992).
+
+and
+
+Boehm H., "Simple GC-safe Compilation", Proceedings
+of the ACM SIGPLAN '96 Conference on Programming Language Design and
+Implementation.
+
+(Some of these are also available from
+http://www.hpl.hp.com/personal/Hans_Boehm/papers/, among other places.)
+
+  Unlike the collector described in the second reference, this collector
+operates either with the mutator stopped during the entire collection
+(default) or incrementally during allocations.  (The latter is supported
+on only a few machines.)  On the most common platforms, it can be built
+with or without thread support.  On a few platforms, it can take advantage
+of a multiprocessor to speed up garbage collection.
+
+  Many of the ideas underlying the collector have previously been explored
+by others.  Notably, some of the run-time systems developed at Xerox PARC
+in the early 1980s conservatively scanned thread stacks to locate possible
+pointers (cf. Paul Rovner, "On Adding Garbage Collection and Runtime Types
+to a Strongly-Typed Statically Checked, Concurrent Language"  Xerox PARC
+CSL 84-7).  Doug McIlroy wrote a simpler fully conservative collector that
+was part of version 8 UNIX (tm), but appears to not have received
+widespread use.
+
+  Rudimentary tools for use of the collector as a leak detector are included
+(see http://www.hpl.hp.com/personal/Hans_Boehm/gc/leak.html),
+as is a fairly sophisticated string package "cord" that makes use of the
+collector.  (See doc/README.cords and H.-J. Boehm, R. Atkinson, and M. Plass,
+"Ropes: An Alternative to Strings", Software Practice and Experience 25, 12
+(December 1995), pp. 1315-1330.  This is very similar to the "rope" package
+in Xerox Cedar, or the "rope" package in the SGI STL or the g++ distribution.)
+
+Further collector documantation can be found at
+
+http://www.hpl.hp.com/personal/Hans_Boehm/gc
+
+
+GENERAL DESCRIPTION
+
+  This is a garbage collecting storage allocator that is intended to be
+used as a plug-in replacement for C's malloc.
+
+  Since the collector does not require pointers to be tagged, it does not
+attempt to ensure that all inaccessible storage is reclaimed.  However,
+in our experience, it is typically more successful at reclaiming unused
+memory than most C programs using explicit deallocation.  Unlike manually
+introduced leaks, the amount of unreclaimed memory typically stays
+bounded.
+
+  In the following, an "object" is defined to be a region of memory allocated
+by the routines described below.  
+
+  Any objects not intended to be collected must be pointed to either
+from other such accessible objects, or from the registers,
+stack, data, or statically allocated bss segments.  Pointers from
+the stack or registers may point to anywhere inside an object.
+The same is true for heap pointers if the collector is compiled with
+ ALL_INTERIOR_POINTERS defined, as is now the default.
+
+Compiling without ALL_INTERIOR_POINTERS may reduce accidental retention
+of garbage objects, by requiring pointers from the heap to to the beginning
+of an object.  But this no longer appears to be a significant
+issue for most programs.
+
+There are a number of routines which modify the pointer recognition
+algorithm.  GC_register_displacement allows certain interior pointers
+to be recognized even if ALL_INTERIOR_POINTERS is nor defined.
+GC_malloc_ignore_off_page allows some pointers into the middle of large objects
+to be disregarded, greatly reducing the probablility of accidental
+retention of large objects.  For most purposes it seems best to compile
+with ALL_INTERIOR_POINTERS and to use GC_malloc_ignore_off_page if
+you get collector warnings from allocations of very large objects.
+See README.debugging for details.
+
+  WARNING: pointers inside memory allocated by the standard "malloc" are not
+seen by the garbage collector.  Thus objects pointed to only from such a
+region may be prematurely deallocated.  It is thus suggested that the
+standard "malloc" be used only for memory regions, such as I/O buffers, that
+are guaranteed not to contain pointers to garbage collectable memory.
+Pointers in C language automatic, static, or register variables,
+are correctly recognized.  (Note that GC_malloc_uncollectable has semantics
+similar to standard malloc, but allocates objects that are traced by the
+collector.)
+
+  WARNING: the collector does not always know how to find pointers in data
+areas that are associated with dynamic libraries.  This is easy to
+remedy IF you know how to find those data areas on your operating
+system (see GC_add_roots).  Code for doing this under SunOS, IRIX 5.X and 6.X,
+HP/UX, Alpha OSF/1, Linux, and win32 is included and used by default.  (See
+README.win32 for win32 details.)  On other systems pointers from dynamic
+library data areas may not be considered by the collector.
+If you're writing a program that depends on the collector scanning
+dynamic library data areas, it may be a good idea to include at least
+one call to GC_is_visible() to ensure that those areas are visible
+to the collector.
+
+  Note that the garbage collector does not need to be informed of shared
+read-only data.  However if the shared library mechanism can introduce
+discontiguous data areas that may contain pointers, then the collector does
+need to be informed.
+
+  Signal processing for most signals may be deferred during collection,
+and during uninterruptible parts of the allocation process.
+Like standard ANSI C mallocs, by default it is unsafe to invoke
+malloc (and other GC routines) from a signal handler while another
+malloc call may be in progress. Removing -DNO_SIGNALS from Makefile
+attempts to remedy that.  But that may not be reliable with a compiler that
+substantially reorders memory operations inside GC_malloc.
+
+  The allocator/collector can also be configured for thread-safe operation.
+(Full signal safety can also be achieved, but only at the cost of two system
+calls per malloc, which is usually unacceptable.)
+WARNING: the collector does not guarantee to scan thread-local storage
+(e.g. of the kind accessed with pthread_getspecific()).  The collector
+does scan thread stacks, though, so generally the best solution is to
+ensure that any pointers stored in thread-local storage are also
+stored on the thread's stack for the duration of their lifetime.
+(This is arguably a longstanding bug, but it hasn't been fixed yet.)
+
+INSTALLATION AND PORTABILITY
+
+  As distributed, the macro SILENT is defined in Makefile.
+In the event of problems, this can be removed to obtain a moderate
+amount of descriptive output for each collection.
+(The given statistics exhibit a few peculiarities.
+Things don't appear to add up for a variety of reasons, most notably
+fragmentation losses.  These are probably much more significant for the
+contrived program "test.c" than for your application.)
+
+  Note that typing "make test" will automatically build the collector
+and then run setjmp_test and gctest. Setjmp_test will give you information
+about configuring the collector, which is useful primarily if you have
+a machine that's not already supported.  Gctest is a somewhat superficial
+test of collector functionality.  Failure is indicated by a core dump or
+a message to the effect that the collector is broken.  Gctest takes about 
+35 seconds to run on a SPARCstation 2. It may use up to 8 MB of memory.  (The
+multi-threaded version will use more.  64-bit versions may use more.)
+"Make test" will also, as its last step, attempt to build and test the
+"cord" string library.  This will fail without an ANSI C compiler, but
+the garbage collector itself should still be usable.
+
+  The Makefile will generate a library gc.a which you should link against.
+Typing "make cords" will add the cord library to gc.a.
+Note that this requires an ANSI C compiler.
+
+  It is suggested that if you need to replace a piece of the collector
+(e.g. GC_mark_rts.c) you simply list your version ahead of gc.a on the
+ld command line, rather than replacing the one in gc.a.  (This will
+generate numerous warnings under some versions of AIX, but it still
+works.)
+
+  All include files that need to be used by clients will be put in the
+include subdirectory.  (Normally this is just gc.h.  "Make cords" adds
+"cord.h" and "ec.h".)
+
+  The collector currently is designed to run essentially unmodified on
+machines that use a flat 32-bit or 64-bit address space.
+That includes the vast majority of Workstations and X86 (X >= 3) PCs.
+(The list here was deleted because it was getting too long and constantly
+out of date.)
+  It does NOT run under plain 16-bit DOS or Windows 3.X.  There are however
+various packages (e.g. win32s, djgpp) that allow flat 32-bit address
+applications to run under those systemsif the have at least an 80386 processor,
+and several of those are compatible with the collector.
+
+  In a few cases (Amiga, OS/2, Win32, MacOS) a separate makefile
+or equivalent is supplied.  Many of these have separate README.system
+files.
+
+  Dynamic libraries are completely supported only under SunOS
+(and even that support is not functional on the last Sun 3 release),
+Linux, IRIX 5&6, HP-PA, Win32 (not Win32S) and OSF/1 on DEC AXP machines.
+On other machines we recommend that you do one of the following:
+
+  1) Add dynamic library support (and send us the code).
+  2) Use static versions of the libraries.
+  3) Arrange for dynamic libraries to use the standard malloc.
+     This is still dangerous if the library stores a pointer to a
+     garbage collected object.  But nearly all standard interfaces
+     prohibit this, because they deal correctly with pointers
+     to stack allocated objects.  (Strtok is an exception.  Don't
+     use it.)
+
+  In all cases we assume that pointer alignment is consistent with that
+enforced by the standard C compilers.  If you use a nonstandard compiler
+you may have to adjust the alignment parameters defined in gc_priv.h.
+
+  A port to a machine that is not byte addressed, or does not use 32 bit
+or 64 bit addresses will require a major effort.  A port to plain MSDOS
+or win16 is hard.
+
+  For machines not already mentioned, or for nonstandard compilers, the
+following are likely to require change:
+
+1.  The parameters in gcconfig.h.
+      The parameters that will usually require adjustment are
+   STACKBOTTOM,  ALIGNMENT and DATASTART.  Setjmp_test
+   prints its guesses of the first two.
+      DATASTART should be an expression for computing the
+   address of the beginning of the data segment.  This can often be
+   &etext.  But some memory management units require that there be
+   some unmapped space between the text and the data segment.  Thus
+   it may be more complicated.   On UNIX systems, this is rarely
+   documented.  But the adb "$m" command may be helpful.  (Note
+   that DATASTART will usually be a function of &etext.  Thus a
+   single experiment is usually insufficient.)
+     STACKBOTTOM is used to initialize GC_stackbottom, which
+   should be a sufficient approximation to the coldest stack address.
+   On some machines, it is difficult to obtain such a value that is
+   valid across a variety of MMUs, OS releases, etc.  A number of
+   alternatives exist for using the collector in spite of this.  See the
+   discussion in gcconfig.h immediately preceding the various
+   definitions of STACKBOTTOM.
+   
+2.  mach_dep.c.
+      The most important routine here is one to mark from registers.
+    The distributed file includes a generic hack (based on setjmp) that
+    happens to work on many machines, and may work on yours.  Try
+    compiling and running setjmp_t.c to see whether it has a chance of
+    working.  (This is not correct C, so don't blame your compiler if it
+    doesn't work.  Based on limited experience, register window machines
+    are likely to cause trouble.  If your version of setjmp claims that
+    all accessible variables, including registers, have the value they
+    had at the time of the longjmp, it also will not work.  Vanilla 4.2 BSD
+    on Vaxen makes such a claim.  SunOS does not.)
+      If your compiler does not allow in-line assembly code, or if you prefer
+    not to use such a facility, mach_dep.c may be replaced by a .s file
+    (as we did for the MIPS machine and the PC/RT).
+      At this point enough architectures are supported by mach_dep.c
+    that you will rarely need to do more than adjust for assembler
+    syntax.
+
+3.  os_dep.c (and gc_priv.h).
+  	  Several kinds of operating system dependent routines reside here.
+  	Many are optional.  Several are invoked only through corresponding
+  	macros in gc_priv.h, which may also be redefined as appropriate.
+      The routine GC_register_data_segments is crucial.  It registers static
+    data areas that must be traversed by the collector. (User calls to
+    GC_add_roots may sometimes be used for similar effect.)
+      Routines to obtain memory from the OS also reside here.
+    Alternatively this can be done entirely by the macro GET_MEM
+    defined in gc_priv.h.  Routines to disable and reenable signals
+    also reside here if they are need by the macros DISABLE_SIGNALS
+    and ENABLE_SIGNALS defined in gc_priv.h.
+      In a multithreaded environment, the macros LOCK and UNLOCK
+    in gc_priv.h will need to be suitably redefined.
+      The incremental collector requires page dirty information, which
+    is acquired through routines defined in os_dep.c.  Unless directed
+    otherwise by gcconfig.h, these are implemented as stubs that simply
+    treat all pages as dirty.  (This of course makes the incremental
+    collector much less useful.)
+
+4.  dyn_load.c
+	This provides a routine that allows the collector to scan data
+	segments associated with dynamic libraries.  Often it is not
+	necessary to provide this routine unless user-written dynamic
+	libraries are used.
+
+  For a different version of UN*X or different machines using the
+Motorola 68000, Vax, SPARC, 80386, NS 32000, PC/RT, or MIPS architecture,
+it should frequently suffice to change definitions in gcconfig.h.
+
+
+THE C INTERFACE TO THE ALLOCATOR
+
+  The following routines are intended to be directly called by the user.
+Note that usually only GC_malloc is necessary.  GC_clear_roots and GC_add_roots
+calls may be required if the collector has to trace from nonstandard places
+(e.g. from dynamic library data areas on a machine on which the 
+collector doesn't already understand them.)  On some machines, it may
+be desirable to set GC_stacktop to a good approximation of the stack base. 
+(This enhances code portability on HP PA machines, since there is no
+good way for the collector to compute this value.)  Client code may include
+"gc.h", which defines all of the following, plus many others.
+
+1)  GC_malloc(nbytes)
+    - allocate an object of size nbytes.  Unlike malloc, the object is
+      cleared before being returned to the user.  Gc_malloc will
+      invoke the garbage collector when it determines this to be appropriate.
+      GC_malloc may return 0 if it is unable to acquire sufficient
+      space from the operating system.  This is the most probable
+      consequence of running out of space.  Other possible consequences
+      are that a function call will fail due to lack of stack space,
+      or that the collector will fail in other ways because it cannot
+      maintain its internal data structures, or that a crucial system
+      process will fail and take down the machine.  Most of these
+      possibilities are independent of the malloc implementation.
+
+2)  GC_malloc_atomic(nbytes)
+    - allocate an object of size nbytes that is guaranteed not to contain any
+      pointers.  The returned object is not guaranteed to be cleared.
+      (Can always be replaced by GC_malloc, but results in faster collection
+      times.  The collector will probably run faster if large character
+      arrays, etc. are allocated with GC_malloc_atomic than if they are
+      statically allocated.)
+
+3)  GC_realloc(object, new_size)
+    - change the size of object to be new_size.  Returns a pointer to the
+      new object, which may, or may not, be the same as the pointer to
+      the old object.  The new object is taken to be atomic iff the old one
+      was.  If the new object is composite and larger than the original object,
+      then the newly added bytes are cleared (we hope).  This is very likely
+      to allocate a new object, unless MERGE_SIZES is defined in gc_priv.h.
+      Even then, it is likely to recycle the old object only if the object
+      is grown in small additive increments (which, we claim, is generally bad
+      coding practice.)
+
+4)  GC_free(object)
+    - explicitly deallocate an object returned by GC_malloc or
+      GC_malloc_atomic.  Not necessary, but can be used to minimize
+      collections if performance is critical.  Probably a performance
+      loss for very small objects (<= 8 bytes).
+
+5)  GC_expand_hp(bytes)
+    - Explicitly increase the heap size.  (This is normally done automatically
+      if a garbage collection failed to GC_reclaim enough memory.  Explicit
+      calls to GC_expand_hp may prevent unnecessarily frequent collections at
+      program startup.)
+
+6)  GC_malloc_ignore_off_page(bytes)
+	- identical to GC_malloc, but the client promises to keep a pointer to
+	  the somewhere within the first 256 bytes of the object while it is
+	  live.  (This pointer should nortmally be declared volatile to prevent
+	  interference from compiler optimizations.)  This is the recommended
+	  way to allocate anything that is likely to be larger than 100Kbytes
+	  or so.  (GC_malloc may result in failure to reclaim such objects.)
+
+7)  GC_set_warn_proc(proc)
+	- Can be used to redirect warnings from the collector.  Such warnings
+	  should be rare, and should not be ignored during code development.
+      
+8) GC_enable_incremental()
+    - Enables generational and incremental collection.  Useful for large
+      heaps on machines that provide access to page dirty information.
+      Some dirty bit implementations may interfere with debugging
+      (by catching address faults) and place restrictions on heap arguments
+      to system calls (since write faults inside a system call may not be
+      handled well).
+
+9) Several routines to allow for registration of finalization code.
+   User supplied finalization code may be invoked when an object becomes
+   unreachable.  To call (*f)(obj, x) when obj becomes inaccessible, use
+	GC_register_finalizer(obj, f, x, 0, 0);
+   For more sophisticated uses, and for finalization ordering issues,
+   see gc.h.
+
+  The global variable GC_free_space_divisor may be adjusted up from its
+default value of 4 to use less space and more collection time, or down for
+the opposite effect.  Setting it to 1 or 0 will effectively disable collections
+and cause all allocations to simply grow the heap.
+
+  The variable GC_non_gc_bytes, which is normally 0, may be changed to reflect
+the amount of memory allocated by the above routines that should not be
+considered as a candidate for collection.  Careless use may, of course, result
+in excessive memory consumption.
+
+  Some additional tuning is possible through the parameters defined
+near the top of gc_priv.h.
+  
+  If only GC_malloc is intended to be used, it might be appropriate to define:
+
+#define malloc(n) GC_malloc(n)
+#define calloc(m,n) GC_malloc((m)*(n))
+
+  For small pieces of VERY allocation intensive code, gc_inl.h
+includes some allocation macros that may be used in place of GC_malloc
+and friends.
+
+  All externally visible names in the garbage collector start with "GC_".
+To avoid name conflicts, client code should avoid this prefix, except when
+accessing garbage collector routines or variables.
+
+  There are provisions for allocation with explicit type information.
+This is rarely necessary.  Details can be found in gc_typed.h.
+
+THE C++ INTERFACE TO THE ALLOCATOR:
+
+  The Ellis-Hull C++ interface to the collector is included in
+the collector distribution.  If you intend to use this, type
+"make c++" after the initial build of the collector is complete.
+See gc_cpp.h for the definition of the interface.  This interface
+tries to approximate the Ellis-Detlefs C++ garbage collection
+proposal without compiler changes.
+
+Cautions:
+1. Arrays allocated without new placement syntax are
+allocated as uncollectable objects.  They are traced by the
+collector, but will not be reclaimed.
+
+2. Failure to use "make c++" in combination with (1) will
+result in arrays allocated using the default new operator.
+This is likely to result in disaster without linker warnings.
+
+3. If your compiler supports an overloaded new[] operator,
+then gc_cpp.cc and gc_cpp.h should be suitably modified.
+
+4. Many current C++ compilers have deficiencies that
+break some of the functionality.  See the comments in gc_cpp.h
+for suggested workarounds.
+
+USE AS LEAK DETECTOR:
+
+  The collector may be used to track down leaks in C programs that are
+intended to run with malloc/free (e.g. code with extreme real-time or
+portability constraints).  To do so define FIND_LEAK in Makefile
+This will cause the collector to invoke the report_leak
+routine defined near the top of reclaim.c whenever an inaccessible
+object is found that has not been explicitly freed.  Such objects will
+also be automatically reclaimed.
+  Productive use of this facility normally involves redefining report_leak
+to do something more intelligent.  This typically requires annotating
+objects with additional information (e.g. creation time stack trace) that
+identifies their origin.  Such code is typically not very portable, and is
+not included here, except on SPARC machines.
+  If all objects are allocated with GC_DEBUG_MALLOC (see next section),
+then the default version of report_leak will report the source file
+and line number at which the leaked object was allocated.  This may
+sometimes be sufficient.  (On SPARC/SUNOS4 machines, it will also report
+a cryptic stack trace.  This can often be turned into a sympolic stack
+trace by invoking program "foo" with "callprocs foo".  Callprocs is
+a short shell script that invokes adb to expand program counter values
+to symbolic addresses.  It was largely supplied by Scott Schwartz.)
+  Note that the debugging facilities described in the next section can
+sometimes be slightly LESS effective in leak finding mode, since in
+leak finding mode, GC_debug_free actually results in reuse of the object.
+(Otherwise the object is simply marked invalid.)  Also note that the test
+program is not designed to run meaningfully in FIND_LEAK mode.
+Use "make gc.a" to build the collector.
+
+DEBUGGING FACILITIES:
+
+  The routines GC_debug_malloc, GC_debug_malloc_atomic, GC_debug_realloc,
+and GC_debug_free provide an alternate interface to the collector, which
+provides some help with memory overwrite errors, and the like.
+Objects allocated in this way are annotated with additional
+information.  Some of this information is checked during garbage
+collections, and detected inconsistencies are reported to stderr.
+
+  Simple cases of writing past the end of an allocated object should
+be caught if the object is explicitly deallocated, or if the
+collector is invoked while the object is live.  The first deallocation
+of an object will clear the debugging info associated with an
+object, so accidentally repeated calls to GC_debug_free will report the
+deallocation of an object without debugging information.  Out of
+memory errors will be reported to stderr, in addition to returning
+NIL.
+
+  GC_debug_malloc checking  during garbage collection is enabled
+with the first call to GC_debug_malloc.  This will result in some
+slowdown during collections.  If frequent heap checks are desired,
+this can be achieved by explicitly invoking GC_gcollect, e.g. from
+the debugger.
+
+  GC_debug_malloc allocated objects should not be passed to GC_realloc
+or GC_free, and conversely.  It is however acceptable to allocate only
+some objects with GC_debug_malloc, and to use GC_malloc for other objects,
+provided the two pools are kept distinct.  In this case, there is a very
+low probablility that GC_malloc allocated objects may be misidentified as
+having been overwritten.  This should happen with probability at most
+one in 2**32.  This probability is zero if GC_debug_malloc is never called.
+
+  GC_debug_malloc, GC_malloc_atomic, and GC_debug_realloc take two
+additional trailing arguments, a string and an integer.  These are not
+interpreted by the allocator.  They are stored in the object (the string is
+not copied).  If an error involving the object is detected, they are printed.
+
+  The macros GC_MALLOC, GC_MALLOC_ATOMIC, GC_REALLOC, GC_FREE, and
+GC_REGISTER_FINALIZER are also provided.  These require the same arguments
+as the corresponding (nondebugging) routines.  If gc.h is included
+with GC_DEBUG defined, they call the debugging versions of these
+functions, passing the current file name and line number as the two
+extra arguments, where appropriate.  If gc.h is included without GC_DEBUG
+defined, then all these macros will instead be defined to their nondebugging
+equivalents.  (GC_REGISTER_FINALIZER is necessary, since pointers to
+objects with debugging information are really pointers to a displacement
+of 16 bytes form the object beginning, and some translation is necessary
+when finalization routines are invoked.  For details, about what's stored
+in the header, see the definition of the type oh in debug_malloc.c)
+
+INCREMENTAL/GENERATIONAL COLLECTION:
+
+The collector normally interrupts client code for the duration of 
+a garbage collection mark phase.  This may be unacceptable if interactive
+response is needed for programs with large heaps.  The collector
+can also run in a "generational" mode, in which it usually attempts to
+collect only objects allocated since the last garbage collection.
+Furthermore, in this mode, garbage collections run mostly incrementally,
+with a small amount of work performed in response to each of a large number of
+GC_malloc requests.
+
+This mode is enabled by a call to GC_enable_incremental().
+
+Incremental and generational collection is effective in reducing
+pause times only if the collector has some way to tell which objects
+or pages have been recently modified.  The collector uses two sources
+of information:
+
+1. Information provided by the VM system.  This may be provided in
+one of several forms.  Under Solaris 2.X (and potentially under other
+similar systems) information on dirty pages can be read from the
+/proc file system.  Under other systems (currently SunOS4.X) it is
+possible to write-protect the heap, and catch the resulting faults.
+On these systems we require that system calls writing to the heap
+(other than read) be handled specially by client code.
+See os_dep.c for details.
+
+2. Information supplied by the programmer.  We define "stubborn"
+objects to be objects that are rarely changed.  Such an object
+can be allocated (and enabled for writing) with GC_malloc_stubborn.
+Once it has been initialized, the collector should be informed with
+a call to GC_end_stubborn_change.  Subsequent writes that store
+pointers into the object must be preceded by a call to
+GC_change_stubborn.
+
+This mechanism performs best for objects that are written only for
+initialization, and such that only one stubborn object is writable
+at once.  It is typically not worth using for short-lived
+objects.  Stubborn objects are treated less efficiently than pointerfree
+(atomic) objects.
+
+A rough rule of thumb is that, in the absence of VM information, garbage
+collection pauses are proportional to the amount of pointerful storage
+plus the amount of modified "stubborn" storage that is reachable during
+the collection.  
+
+Initial allocation of stubborn objects takes longer than allocation
+of other objects, since other data structures need to be maintained.
+
+We recommend against random use of stubborn objects in client
+code, since bugs caused by inappropriate writes to stubborn objects
+are likely to be very infrequently observed and hard to trace.  
+However, their use may be appropriate in a few carefully written
+library routines that do not make the objects themselves available
+for writing by client code.
+
+
+BUGS:
+
+  Any memory that does not have a recognizable pointer to it will be
+reclaimed.  Exclusive-or'ing forward and backward links in a list
+doesn't cut it.
+  Some C optimizers may lose the last undisguised pointer to a memory
+object as a consequence of clever optimizations.  This has almost
+never been observed in practice.  Send mail to boehm@acm.org
+for suggestions on how to fix your compiler.
+  This is not a real-time collector.  In the standard configuration,
+percentage of time required for collection should be constant across
+heap sizes.  But collection pauses will increase for larger heaps.
+(On SPARCstation 2s collection times will be on the order of 300 msecs
+per MB of accessible memory that needs to be scanned.  Your mileage
+may vary.)  The incremental/generational collection facility helps,
+but is portable only if "stubborn" allocation is used.
+  Please address bug reports to boehm@acm.org.  If you are
+contemplating a major addition, you might also send mail to ask whether
+it's already been done (or whether we tried and discarded it).
+
diff --git a/gc/doc/README.Mac b/gc/doc/README.Mac
new file mode 100644
index 0000000..04f4682
--- /dev/null
+++ b/gc/doc/README.Mac
@@ -0,0 +1,385 @@
+Patrick Beard's Notes for building GC v4.12 with CodeWarrior Pro 2:
+----------------------------------------------------------------------------
+The current build environment for the collector is CodeWarrior Pro 2.
+Projects for CodeWarrior Pro 2 (and for quite a few older versions)
+are distributed in the file Mac_projects.sit.hqx. The project file
+:Mac_projects:gc.prj builds static library versions of the collector.
+:Mac_projects:gctest.prj builds the GC test suite.
+
+Configuring the collector is still done by editing the files
+:Mac_files:MacOS_config.h and :Mac_files:MacOS_Test_config.h.
+
+Lars Farm's suggestions on building the collector:
+----------------------------------------------------------------------------
+Garbage Collection on MacOS - a manual 'MakeFile'
+-------------------------------------------------
+
+Project files and IDE's are great on the Macintosh, but they do have
+problems when used as distribution media. This note tries to provide
+porting instructions in pure TEXT form to avoid those problems. A manual
+'makefile' if you like.
+
+    GC version:     4.12a2
+    Codewarrior:    CWPro1
+    date:           18 July 1997
+
+The notes may or may not apply to earlier or later versions of the
+GC/CWPro. Actually, they do apply to earlier versions of both except that
+until recently a project could only build one target so each target was a
+separate project. The notes will most likely apply to future versions too.
+Possibly with minor tweaks.
+
+This is just to record my experiences. These notes do not mean I now
+provide a supported port of the GC to MacOS. It works for me. If it works
+for you, great. If it doesn't, sorry, try again...;-) Still, if you find
+errors, please let me know.
+
+    mailto:         lars.farm@ite.mh.se
+
+    address:        Lars Farm
+                    Krönvägen 33b
+                    856 44 Sundsvall
+                    Sweden
+
+Porting to MacOS is a bit more complex than it first seems. Which MacOS?
+68K/PowerPC? Which compiler? Each supports both 68K and PowerPC and offer a
+large number of (unique to each environment) compiler settings. Each
+combination of compiler/68K/PPC/settings require a unique combination of
+standard libraries. And the IDE's does not select them for you. They don't
+even check that the library is built with compatible setting and this is
+the major source of problems when porting the GC (and otherwise too).
+
+You will have to make choices when you configure the GC. I've made some
+choices here, but there are other combinations of settings and #defines
+that work too.
+
+As for target settings the major obstacles may be:
+- 68K Processor: check "4-byte Ints".
+- PPC Processor: uncheck "Store Static Data in TOC".
+
+What you need to do:
+===================
+
+1) Build the GC as a library
+2) Test that the library works with 'test.c'.
+3) Test that the C++ interface 'gc_cpp.cc/h' works with 'test_cpp.cc'.
+
+1) The Libraries:
+=================
+I made one project with four targets (68K/PPC tempmem or appheap). One target
+will suffice if you're able to decide which one you want. I wasn't...
+
+Codewarrior allows a large number of compiler/linker settings. I used these:
+
+Settings shared by all targets:
+------------------------------
+o Access Paths:
+  - User Paths:   the GC folder
+  - System Paths: {Compiler}:Metrowerks Standard Library:
+                  {Compiler}:MacOS Support:Headers:
+                  {Compiler}:MacOS Support:MacHeaders:
+o C/C++ language:
+  - inlining: normal
+  - direct to SOM: off
+  - enable/check: exceptions, RTTI, bool (and if you like pool strings)
+
+PowerPC target settings
+-----------------------
+o Target Settings:
+  - name of target
+  - MacOS PPC Linker
+o PPC Target
+  - name of library
+o C/C++ language
+  - prefix file as described below
+o PPC Processor
+  - Struct Alignment: PowerPC
+  - uncheck "Store Static Data in TOC" -- important!
+    I don't think the others matter, I use full optimization and its ok
+o PPC Linker
+  - Factory Settings (SYM file with full paths, faster linking, dead-strip
+    static init, Main: __start)
+
+
+68K target settings
+-------------------
+o Target Settings:
+  - name of target
+  - MacOS 68K Linker
+o 68K Target
+  - name of library
+  - A5 relative data
+o C/C++ language
+  - prefix file as described below
+o 68K Processor
+  - Code model: smart
+  - Struct alignment: 68K
+  - FP: SANE
+  - enable 4-Byte Ints -- important!
+    I don't think the others matter. I selected...
+  - enable: 68020
+  - enable: global register allocation
+o IR Optimizer
+  - enable: Optimize Space, Optimize Speed
+    I suppose the others would work too, but haven't tried...
+o 68K Linker
+  - Factory Settings (New Style MacsBug,SYM file with full paths,
+    A6 Frames, fast link, Merge compiler glue into segment 1,
+    dead-strip static init)
+
+Prefix Files to configure the GC sources
+----------------------------------------
+The Codewarrior equivalent of commandline compilers -DNAME=X is to use
+prefix-files. A TEXT file that is automatically #included before the first byte
+of every source file. I used these:
+
+---- ( cut here ) ----  gc_prefix_tempmem.h     -- 68K and PPC -----
+    #include "gc_prefix_common.h"
+    #undef USE_TEMPORARY_MEMORY
+    #define USE_TEMPORARY_MEMORY
+---- ( cut here ) ----  gc_prefix_appmem.h      -- 68K and PPC -----
+    #include "gc_prefix_common.h"
+    #undef USE_TEMPORARY_MEMORY
+//  #define USE_TEMPORARY_MEMORY
+
+---- ( cut here ) ----  gc_prefix_common.h      --------------------
+// gc_prefix_common.h
+// ------------------
+// Codewarrior prefix file to configure the GC libraries
+//
+//   prefix files are the Codewarrior equivalent of the
+//   command line option -Dname=x frequently seen in makefiles
+
+#if !__MWERKS__
+  #error only tried this with Codewarrior
+#endif
+
+#if macintosh
+  #define MSL_USE_PRECOMPILED_HEADERS 0
+  #include <ansi_prefix.mac.h>
+  #ifndef __STDC__
+    #define __STDC__ 0
+  #endif
+
+  //  See list of #defines to configure the library in: 'MakeFile'
+  //  see also README
+
+  #define SILENT                // no collection messages. In case
+                                // of trouble you might want this off
+  #define ALL_INTERIOR_POINTERS // follows interior pointers.
+//#define DONT_ADD_BYTE_AT_END  // disables the padding if defined.
+//#define SMALL_CONFIG          // whether to use a smaller heap.
+  #define NO_SIGNALS            // signals aren't real on the Macintosh.
+  #define ATOMIC_UNCOLLECTABLE  // GC_malloc_atomic_uncollectable()
+
+  // define either or none as per personal preference
+  //   used in malloc.c
+  #define REDIRECT_MALLOC GC_malloc
+//#define REDIRECT_MALLOC GC_malloc_uncollectable
+  // if REDIRECT_MALLOC is #defined make sure that the GC library
+  // is listed before the ANSI/ISO libs in the Codewarrior
+  // 'Link order' panel
+//#define IGNORE_FREE
+
+  // mac specific configs
+//#define USE_TEMPORARY_MEMORY    // use Macintosh temporary memory.
+//#define SHARED_LIBRARY_BUILD    // build for use in a shared library.
+
+#else
+  // could build Win32 here too, or in the future
+  // Rhapsody PPC-mach, Rhapsody PPC-MacOS,
+  // Rhapsody Intel-mach, Rhapsody Intel-Win32,...
+  // ... ugh this will get messy ...
+#endif
+
+// make sure ints are at least 32-bit
+// ( could be set to 16-bit by compiler settings (68K) )
+
+struct gc_private_assert_intsize_{ char x[ sizeof(int)>=4 ? 1 : 0 ]; };
+
+#if __powerc
+  #if __option(toc_data)
+    #error turn off "store static data in TOC" when using GC
+    //     ... or find a way to add TOC to the root set...(?)
+  #endif
+#endif
+---- ( cut here ) ----  end of gc_prefix_common.h  -----------------
+
+Files to  build the GC libraries:
+--------------------------------
+    allchblk.c
+    alloc.c
+    blacklst.c
+    checksums.c
+    dbg_mlc.c
+    finalize.c
+    headers.c
+    mach_dep.c
+    MacOS.c    -- contains MacOS code
+    malloc.c
+    mallocx.c
+    mark.c
+    mark_rts.c
+    misc.c
+    new_hblk.c
+    obj_map.c
+    os_dep.c   -- contains MacOS code
+    ptr_chck.c
+    reclaim.c
+    stubborn.c
+    typd_mlc.c
+    gc++.cc    -- this is 'gc_cpp.cc' with less 'inline' and
+               -- throw std::bad_alloc when out of memory
+               -- gc_cpp.cc works just fine too
+
+2) Test that the library works with 'test.c'.
+=============================================
+
+The test app is just an ordinary ANSI-C console app. Make sure settings
+match the library you're testing.
+
+Files
+-----
+    test.c
+    the GC library to test        -- link order before ANSI libs
+    suitable Mac+ANSI libraries
+
+prefix:
+------
+---- ( cut here ) ----  gc_prefix_testlib.h     -- all libs -----
+#define MSL_USE_PRECOMPILED_HEADERS 0
+#include <ansi_prefix.mac.h>
+#undef NDEBUG
+
+#define ALL_INTERIOR_POINTERS	/* for GC_priv.h */
+---- ( cut here ) ----
+
+3) Test that the C++ interface 'gc_cpp.cc/h' works with 'test_cpp.cc'.
+
+The test app is just an ordinary ANSI-C console app. Make sure settings match
+the library you're testing.
+
+Files
+-----
+    test_cpp.cc
+    the GC library to test        -- link order before ANSI libs
+    suitable Mac+ANSI libraries
+
+prefix:
+------
+same as for test.c
+
+For convenience I used one test-project with several targets so that all
+test apps are build at once. Two for each library to test: test.c and
+gc_app.cc. When I was satisfied that the libraries were ok. I put the
+libraries + gc.h + the c++ interface-file in a folder that I then put into
+the MSL hierarchy so that I don't have to alter access-paths in projects
+that use the GC.
+
+After that, just add the proper GC library to your project and the GC is in
+action! malloc will call GC_malloc and free GC_free, new/delete too. You
+don't have to call free or delete. You may have to be a bit cautious about
+delete if you're freeing other resources than RAM. See gc_cpp.h. You can
+also keep coding as always with delete/free. That works too. If you want,
+"include <gc.h> and tweak it's use a bit.
+
+Symantec SPM
+============
+It has been a while since I tried the GC in SPM, but I think that the above
+instructions should be sufficient to guide you through in SPM too. SPM
+needs to know where the global data is. Use the files 'datastart.c' and
+'dataend.c'. Put 'datastart.c' at the top of your project and 'dataend.c'
+at the bottom  of your project so that all data is surrounded. This is not
+needed in Codewarrior because it provides intrinsic variables
+__datastart__, __data_end__ that wraps all globals.
+
+Source Changes (GC 4.12a2)
+==========================
+Very few. Just one tiny in the GC, not strictly needed.
+- MacOS.c line 131 in routine GC_MacFreeTemporaryMemory()
+  change #       if !defined(SHARED_LIBRARY_BUILD)
+  to     #       if !defined(SILENT) && !defined(SHARED_LIBRARY_BUILD)
+  To turn off a message when the application quits (actually, I faked
+  this change by #defining SHARED_LIBRARY_BUILD in a statically linked
+  library for more than a year without ill effects but perhaps this is
+  better).
+
+- test_cpp.cc
+  made the first lines of main() look like this:
+  ------------
+  int main( int argc, char* argv[] ) {
+  #endif
+  #if macintosh                             // MacOS
+    char* argv_[] = {"test_cpp","10"};      //   doesn't
+    argv=argv_;                             //     have a
+    argc = sizeof(argv_)/sizeof(argv_[0]);  //       commandline
+  #endif                                    //
+
+  int i, iters, n;
+  # ifndef __GNUC__
+   alloc dummy_to_fool_the_compiler_into_doing_things_it_currently_cant_handle;
+  ------------
+
+- config.h [now gcconfig.h]
+  __MWERKS__ does not have to mean MACOS. You can use Codewarrior to
+  build a Win32 or BeOS library and soon a Rhapsody library. You may
+  have to change that #if...
+
+
+
+   It worked for me, hope it works for you.
+
+   Lars Farm
+   18 July 1997
+----------------------------------------------------------------------------
+
+
+Patrick Beard's instructions (may be dated):
+
+v4.3 of the collector now runs under Symantec C++/THINK C v7.0.4, and
+Metrowerks C/C++ v4.5 both 68K and PowerPC. Project files are provided
+to build and test the collector under both development systems.
+
+Configuration
+-------------
+
+To configure the collector, under both development systems, a prefix file
+is used to set preprocessor directives. This file is called "MacOS_config.h".
+Also to test the collector, "MacOS_Test_config.h" is provided.
+
+Testing
+-------
+
+To test the collector (always a good idea), build one of the gctest projects,
+gctest.¹ (Symantec C++/THINK C), mw/gctest.68K.¹, or mw/gctest.PPC.¹. The
+test will ask you how many times to run; 1 should be sufficient.
+
+Building 
+--------
+
+For your convenience project files for the major Macintosh development
+systems are provided.
+
+For Symantec C++/THINK C, you must build the two projects gclib-1.¹ and
+gclib-2.¹. It has to be split up because the collector has more than 32k
+of static data and no library can have more than this in the Symantec
+environment. (Future versions will probably fix this.)
+
+For Metrowerks C/C++ 4.5 you build gc.68K.¹/gc.PPC.¹ and the result will
+be a library called gc.68K.lib/gc.PPC.lib.
+
+Using
+-----
+
+Under Symantec C++/THINK C, you can just add the gclib-1.¹ and gclib-2.¹
+projects to your own project. Under Metrowerks, you add gc.68K.lib or
+gc.PPC.lib and two additional files. You add the files called datastart.c
+and dataend.c to your project, bracketing all files that use the collector.
+See mw/gctest.¹ for an example.
+
+Include the projects/libraries you built above into your own project,
+#include "gc.h", and call GC_malloc. You don't have to call GC_free.
+
+
+Patrick C. Beard
+January 4, 1995
diff --git a/gc/doc/README.MacOSX b/gc/doc/README.MacOSX
new file mode 100644
index 0000000..2abf0b4
--- /dev/null
+++ b/gc/doc/README.MacOSX
@@ -0,0 +1,27 @@
+While the GC should work on MacOS X Server, MacOS X and Darwin, I only tested
+it on MacOS X Server.
+I've added a PPC assembly version of GC_push_regs(), thus the setjmp() hack is
+no longer necessary. Incremental collection is supported via mprotect/signal.
+The current solution isn't really optimal because the signal handler must decode
+the faulting PPC machine instruction in order to find the correct heap address.
+Further, it must poke around in the register state which the kernel saved away
+in some obscure register state structure before it calls the signal handler -
+needless to say the layout of this structure is no where documented.
+Threads and dynamic libraries are not yet supported (adding dynamic library
+support via the low-level dyld API shouldn't be that hard).
+
+The original MacOS X port was brought to you by Andrew Stone.
+
+
+June, 1 2000
+
+Dietmar Planitzer
+dave.pl@ping.at
+
+Note from Andrew Begel:
+
+One more fix to enable gc.a to link successfully into a shared library for
+MacOS X. You have to add -fno-common to the CFLAGS in the Makefile. MacOSX
+disallows common symbols in anything that eventually finds its way into a
+shared library. (I don't completely understand why, but -fno-common seems to
+work and doesn't mess up the garbage collector's functionality).
diff --git a/gc/doc/README.OS2 b/gc/doc/README.OS2
new file mode 100644
index 0000000..5345bbd
--- /dev/null
+++ b/gc/doc/README.OS2
@@ -0,0 +1,6 @@
+The code assumes static linking, and a single thread.  The editor de has
+not been ported.  The cord test program has.  The supplied OS2_MAKEFILE
+assumes the IBM C Set/2 environment, but the code shouldn't.
+
+Since we haven't figured out hoe to do perform partial links or to build static
+libraries, clients currently need to link against a long list of executables.
diff --git a/gc/doc/README.amiga b/gc/doc/README.amiga
new file mode 100644
index 0000000..730dce3
--- /dev/null
+++ b/gc/doc/README.amiga
@@ -0,0 +1,322 @@
+===========================================================================
+            Kjetil S. Matheussen's notes (28-11-2000)
+===========================================================================
+Compiles under SAS/C again. Should allso still compile under other
+amiga compilers without big changes. I haven't checked if it still
+works under gcc, because I don't have gcc for amiga. But I have
+updated 'Makefile', and hope it compiles fine.
+
+
+WHATS NEW:
+
+1.
+   Made a pretty big effort in preventing GCs allocating-functions from returning
+   chip-mem.
+
+   The lower part of the new file AmigaOS.c does this in various ways, mainly by
+   wrapping GC_malloc, GC_malloc_atomic, GC_malloc_uncollectable,
+   GC_malloc_atomic_uncollectable, GC_malloc_stubborn, GC_malloc_ignore_off_page
+   and GC_malloc_atomic_ignore_off_page. GC_realloc is allso wrapped, but
+   doesn't do the same effort in preventing to return chip-mem.
+   Other allocating-functions (f.ex. GC_*_typed_) can probably be
+   used without any problems, but beware that the warn hook will not be called.
+   In case of problems, don't define GC_AMIGA_FASTALLOC.
+
+   Programs using more time actually using the memory allocated
+   (instead of just allocate and free rapidly) have
+   the most to earn on this, but even gctest now normally runs twice
+   as fast and uses less memory, on my poor 8MB machine.
+
+   The changes have only effect when there is no more
+   fast-mem left. But with the way GC works, it
+   could happen quite often. Beware that an atexit handler had to be added,
+   so using the abort() function will make a big memory-loss.
+   If you absolutely must call abort() instead of exit(), try calling
+   the GC_amiga_free_all_mem function before abort().
+
+   New amiga-spesific compilation flags:
+
+   GC_AMIGA_FASTALLOC - By NOT defining this option, GC will work like before,
+                        it will not try to force fast-mem out of the OS, and
+                        it will use normal calloc for allocation, and the rest
+                        of the following flags will have no effect.
+
+   GC_AMIGA_ONLYFAST - Makes GC never to return chip-mem. GC_AMIGA_RETRY have
+                       no effect if this flag is set.
+
+   GC_AMIGA_GC - If gc returns NULL, do a GC_gcollect, and try again. This
+                 usually is a success with the standard GC configuration. 
+                 It is allso the most important flag to set to prevent
+                 GC from returning chip-mem. Beware that it slows down a lot
+                 when a program is rapidly allocating/deallocating when
+                 theres either very little fast-memory left or verly little
+                 chip-memory left. Its not a very common situation, but gctest
+                 sometimes (very rare) use many minutes because of this.
+
+   GC_AMIGA_RETRY - If gc succeed allocating memory, but it is chip-mem,
+                    try again and see if it is fast-mem. Most of the time,
+                    it will actually return fast-mem for the second try.
+                    I have set max number of retries to 9 or size/5000. You
+                    can change this if you like. (see GC_amiga_rec_alloc())
+
+   GC_AMIGA_PRINTSTATS - Gather some statistics during the execution of a
+                         program, and prints out the info when the atexit-handler
+                         is called.
+
+   My reccomendation is to set all this flags, except GC_AMIGA_PRINTSTATS and
+   GC_AMIGA_ONLYFAST.
+
+   If your program demands high response-time, you should
+   not define GC_AMIGA_GC, and possible allso define GC_AMIGA_ONLYFAST.
+   GC_AMIGA_RETRY does not seem to slow down much.
+
+   Allso, when compiling up programs, and GC_AMIGA_FASTALLOC was not defined when
+   compilling gc, you can define GC_AMIGA_MAKINGLIB to avoid having these allocation-
+   functions wrapped. (see gc.h)
+
+   Note that GC_realloc must not be called before any of
+   the other above mentioned allocating-functions have been called. (shouldn't be
+   any programs doing so either, I hope).
+
+   Another note. The allocation-function is wrapped when defining
+   GC_AMIGA_FASTALLOC by letting the function go thru the new
+   GC_amiga_allocwrapper_do function-pointer (see gc.h). Means that
+   sending function-pointers, such as GC_malloc, GC_malloc_atomic, etc.,
+   for later to be called like f.ex this, (*GC_malloc_functionpointer)(size),
+   will not wrap the function. This is normally not a big problem, unless
+   all allocation function is called like this, which will cause the
+   atexit un-allocating function never to be called. Then you either
+   have to manually add the atexit handler, or call the allocation-
+   functions function-pointer functions like this;
+   (*GC_amiga_allocwrapper_do)(size,GC_malloc_functionpointer).
+   There are probably better ways this problem could be handled, unfortunately,
+   I didn't find any without rewriting or replacing a lot of the GC-code, which
+   I really didn't want to. (Making new GC_malloc_* functions, and just
+   define f.ex GC_malloc as GC_amiga_malloc should allso work).
+
+
+   New amiga-spesific function:
+
+     void GC_amiga_set_toany(void (*func)(void));
+
+   'func' is a function that will be called right before gc has to change
+   allocation-method from MEMF_FAST to MEMF_ANY. Ie. when it is likely
+   it will return chip-mem.
+
+
+2. A few small compiler-spesific additions to make it compile with SAS/C again.
+
+3. Updated and rewritten the smakefile, so that it works again and that
+   the "unnecesarry" 'SCOPTIONS' files could be removed. Allso included
+   the cord-smakefile stuff in the main smakefile, so that the cord smakefile
+   could be removed too. By writing smake -f Smakefile.smk, both gc.lib and
+   cord.lib will be made.
+
+
+
+STILL MISSING:
+
+Programs can not be started from workbench, at least not for SAS/C. (Martin
+Tauchmanns note about that it now works with workbench is definitely wrong
+when concerning SAS/C). I guess it works if you use the old "#if 0'ed"-code,
+but I haven't tested it. I think the reason for MT to replace the
+"#if 0'ed"-code was only because it was a bit to SAS/C-spesific. But I
+don't know. An iconx-script solves this problem anyway.
+
+
+BEWARE!
+
+-To run gctest, set the stack to around 200000 bytes first.
+-SAS/C-spesific: cord will crash if you compile gc.lib with
+ either parm=reg or parm=both. (missing legal prototypes for
+ function-pointers someplace is the reason I guess.).
+
+
+tested with software: Radium, http://www.stud.ifi.uio.no/~ksvalast/radium/
+
+tested with hardware: MC68060
+
+
+-ksvalast@ifi.uio.no
+
+
+===========================================================================
+			   Martin Tauchmann's notes		(1-Apr-99)
+===========================================================================
+
+Works now, also with the GNU-C compiler V2.7.2.1. <ftp://ftp.unina.it/pub/amiga/geekgadgets/amiga/m68k/snapshots/971125/amiga-bin/>
+Modify the `Makefile`
+CC=cc $(ABI_FLAG)
+to
+CC=gcc $(ABI_FLAG)
+
+TECHNICAL NOTES
+
+- `GC_get_stack_base()`, `GC_register_data_segments()` works now with every
+   C compiler; also Workbench.
+
+- Removed AMIGA_SKIP_SEG, but the Code-Segment must not be scanned by GC.
+
+
+PROBLEMS
+- When the Linker, does`t merge all Code-Segments to an single one. LD of GCC
+  do it always.
+
+- With ixemul.library V47.3, when an GC program launched from another program
+  (example: `Make` or `if_mach M68K AMIGA gctest`), `GC_register_data_segments()`
+  found the Segment-List of the caller program.
+  Can be fixed, if the run-time initialization code (for C programs, usually *crt0*)
+  support `__data` and `__bss`.
+
+- PowerPC Amiga currently not supported.
+
+- Dynamic libraries (dyn_load.c) not supported.
+
+
+TESTED WITH SOFTWARE
+
+`Optimized Oberon 2 C` (oo2c) <http://cognac.informatik.uni-kl.de/download/index.html>
+
+
+TESTED WITH HARDWARE
+
+MC68030
+
+
+CONTACT
+
+Please, contact me at <martintauchmann@bigfoot.com>, when you change the
+Amiga port. <http://martintauchmann.home.pages.de>
+ 
+===========================================================================
+			   Michel Schinz's notes
+===========================================================================
+WHO DID WHAT
+
+The original Amiga port was made by Jesper Peterson. I (Michel Schinz)
+modified it slightly to reflect the changes made in the new official
+distributions, and to take advantage of the new SAS/C 6.x features. I also
+created a makefile to compile the "cord" package (see the cord
+subdirectory).
+
+TECHNICAL NOTES
+
+In addition to Jesper's notes, I have the following to say:
+
+- Starting with version 4.3, gctest checks to see if the code segment is
+  added to the root set or not, and complains if it is. Previous versions
+  of this Amiga port added the code segment to the root set, so I tried to
+  fix that. The only problem is that, as far as I know, it is impossible to
+  know which segments are code segments and which are data segments (there
+  are indeed solutions to this problem, like scanning the program on disk
+  or patch the LoadSeg functions, but they are rather complicated). The
+  solution I have chosen (see os_dep.c) is to test whether the program
+  counter is in the segment we are about to add to the root set, and if it
+  is, to skip the segment. The problems are that this solution is rather
+  awkward and that it works only for one code segment. This means that if
+  your program has more than one code segment, all of them but one will be
+  added to the root set. This isn't a big problem in fact, since the
+  collector will continue to work correctly, but it may be slower.
+
+  Anyway, the code which decides whether to skip a segment or not can be
+  removed simply by not defining AMIGA_SKIP_SEG. But notice that if you do
+  so, gctest will complain (it will say that "GC_is_visible produced wrong
+  failure indication"). However, it may be useful if you happen to have
+  pointers stored in a code segment (you really shouldn't).
+
+  If anyone has a good solution to the problem of finding, when a program
+  is loaded in memory, whether a segment is a code or a data segment,
+  please let me know.
+
+PROBLEMS
+
+If you have any problem with this version, please contact me at
+schinz@alphanet.ch (but do *not* send long files, since we pay for
+every mail!).
+
+===========================================================================
+			  Jesper Peterson's notes
+===========================================================================
+
+ADDITIONAL NOTES FOR AMIGA PORT
+
+These notes assume some familiarity with Amiga internals.
+
+WHY I PORTED TO THE AMIGA
+
+The sole reason why I made this port was as a first step in getting
+the Sather(*) language on the Amiga. A port of this language will
+be done as soon as the Sather 1.0 sources are made available to me.
+Given this motivation, the garbage collection (GC) port is rather
+minimal.
+
+(*) For information on Sather read the comp.lang.sather newsgroup.
+
+LIMITATIONS
+
+This port assumes that the startup code linked with target programs
+is that supplied with SAS/C versions 6.0 or later. This allows
+assumptions to be made about where to find the stack base pointer
+and data segments when programs are run from WorkBench, as opposed
+to running from the CLI. The compiler dependent code is all in the
+GC_get_stack_base() and GC_register_data_segments() functions, but
+may spread as I add Amiga specific features.
+
+Given that SAS/C was assumed, the port is set up to be built with
+"smake" using the "SMakefile". Compiler options in "SCoptions" can
+be set with "scopts" program. Both "smake" and "scopts" are part of
+the SAS/C commercial development system.
+
+In keeping with the porting philosophy outlined above, this port
+will not behave well with Amiga specific code. Especially not inter-
+process comms via messages, and setting up public structures like
+Intuition objects or anything else in the system lists. For the
+time being the use of this library is limited to single threaded
+ANSI/POSIX  compliant or near-complient code. (ie. Stick to stdio
+for now). Given this limitation there is currently no mechanism for
+allocating "CHIP" or "PUBLIC" memory under the garbage collector.
+I'll add this after giving it considerable thought. The major
+problem is the entire physical address space may have to me scanned,
+since there is no telling who we may have passed memory to.
+
+If you allocate your own stack in client code, you will have to
+assign the pointer plus stack size to GC_stackbottom.
+
+The initial stack size of the target program can be compiled in by
+setting the __stack symbol (see SAS documentaion). It can be over-
+ridden from the CLI by running the AmigaDOS "stack" program, or from
+the WorkBench by setting the stack size in the tool types window.
+
+SAS/C COMPILER OPTIONS (SCoptions)
+
+You may wish to check the "CPU" code option is appropriate for your
+intended target system.
+
+Under no circumstances set the "StackExtend" code option in either
+compiling the library or *ANY* client code.
+
+All benign compiler warnings have been suppressed. These mainly
+involve lack of prototypes in the code, and dead assignments
+detected by the optimizer.
+
+THE GOOD NEWS
+
+The library as it stands is compatible with the GigaMem commercial
+virtual memory software, and probably similar PD software.
+
+The performance of "gctest" on an Amiga 2630 (68030 @ 25Mhz)
+compares favourably with an HP9000 with similar architecture (a 325
+with a 68030 I think).
+
+-----------------------------------------------------------------------
+
+The Amiga port has been brought to you by:
+
+Jesper Peterson.
+
+jep@mtiame.mtia.oz.au		(preferred, but 1 week turnaround)
+jep@orca1.vic.design.telecom.au (that's orca<one>, 1 day turnaround)
+
+At least one of these addresses should be around for a while, even
+though I don't work for either of the companies involved.
+
diff --git a/gc/doc/README.autoconf b/gc/doc/README.autoconf
new file mode 100644
index 0000000..53fcf5a
--- /dev/null
+++ b/gc/doc/README.autoconf
@@ -0,0 +1,59 @@
+As of GC6.0alpha8, we attempt to support GNU-style builds based on automake,
+autoconf and libtool.  This is based almost entirely on Tom Tromey's work
+with gcj.
+
+To build and install libraries use
+
+configure; make; make install
+
+The advantages of this process are:
+
+1) It should eventually do a better job of automatically determining the
+right compiler to use, etc.  It probably already does in some cases.
+
+2) It tries to automatically set a good set of default GC parameters for
+the platform (e.g. thread support).  It provides an easier way to configure
+some of the others.
+
+3) It integrates better with other projects using a GNU-style build process.
+
+4) It builds both dynamic and static libraries.
+
+The known disadvantages are:
+
+1) The build scripts are much more complex and harder to debug (though largely
+standard).  I don't understand them all, and there's probably lots of redundant
+stuff.
+
+2) It probably doesn't work on all Un*x-like platforms yet.  It probably will
+never work on the rest.
+
+3) The scripts are not yet complete.  Some of the standard GNU targets don't
+yet work.  (Corrections/additions are very welcome.)
+
+The distribution should contain all files needed to run "configure" and "make",
+as well as the sources needed to regenerate the derived files.  (If I missed
+some, please let me know.)
+
+Note that the distribution comes with a "Makefile" which will be overwritten
+by "configure" with one that is not at all equiavelent to the original.  The
+distribution contains a copy of the original "Makefile" in "Makefile.direct". 
+
+Important options to configure:
+
+  --prefix=PREFIX         install architecture-independent files in PREFIX
+                          [/usr/local]
+  --exec-prefix=EPREFIX   install architecture-dependent files in EPREFIX
+                          [same as prefix]
+  --enable-threads=TYPE   choose threading package
+  --enable-parallel-mark  parallelize marking and free list construction
+  --enable-full-debug	include full support for pointer backtracing etc.
+
+Unless --prefix is set (or --exec-prefix or one of the more obscure options),
+make install will install libgc.a and libgc.so in /usr/local/bin, which
+would typically require the "make install" to be run as root.
+
+Most commonly --enable-threads=posix or will be needed.  --enable-parallel-mark
+is recommended for multiprocessors if it is supported on the platform.
+
+
diff --git a/gc/doc/README.changes b/gc/doc/README.changes
new file mode 100644
index 0000000..c018c8b
--- /dev/null
+++ b/gc/doc/README.changes
@@ -0,0 +1,1408 @@
+This is a rough history of garbage collector bugs and versions.
+
+This has been maintained with varying diligence over the years.
+
+I made an attempt to include recent contributors here.  I apologize for any
+omissions.
+
+-------------------------
+
+  Version 1.3 and immediately preceding versions contained spurious
+assembly language assignments to TMP_SP.  Only the assignment in the PC/RT
+code is necessary.  On other machines, with certain compiler options,
+the assignments can lead to an unsaved register being overwritten.
+Known to cause problems under SunOS 3.5 WITHOUT the -O option.  (With
+-O the compiler recognizes it as dead code.  It probably shouldn't,
+but that's another story.)
+
+  Version 1.4 and earlier versions used compile time determined values
+for the stack base.  This no longer works on Sun 3s, since Sun 3/80s use
+a different stack base.  We now use a straightforward heuristic on all
+machines on which it is known to work (incl. Sun 3s) and compile-time
+determined values for the rest.  There should really be library calls
+to determine such values.
+
+  Version 1.5 and earlier did not ensure 8 byte alignment for objects
+allocated on a sparc based machine.
+
+  Version 1.8 added ULTRIX support in gc_private.h.
+  
+  Version 1.9 fixed a major bug in gc_realloc.
+  
+  Version 2.0 introduced a consistent naming convention for collector
+routines and added support for registering dynamic library data segments
+in the standard mark_roots.c.  Most of the data structures were revamped.
+The treatment of interior pointers was completely changed.  Finalization
+was added.  Support for locking was added.  Object kinds were added.
+We added a black listing facility to avoid allocating at addresses known
+to occur as integers somewhere in the address space.  Much of this
+was accomplished by adapting ideas and code from the PCR collector.
+The test program was changed and expanded.
+
+  Version 2.1 was the first stable version since 1.9, and added support
+for PPCR.
+
+  Version 2.2 added debugging allocation, and fixed various bugs.  Among them:
+- GC_realloc could fail to extend the size of the object for certain large object sizes.
+- A blatant subscript range error in GC_printf, which unfortunately
+  wasn't exercised on machines with sufficient stack alignment constraints.
+- GC_register_displacement did the wrong thing if it was called after
+  any allocation had taken place.
+- The leak finding code would eventually break after 2048 byte
+  byte objects leaked.
+- interface.c didn't compile.
+- The heap size remained much too small for large stacks.
+- The stack clearing code behaved badly for large stacks, and perhaps
+  on HP/PA machines.
+
+  Version 2.3 added ALL_INTERIOR_POINTERS and fixed the following bugs:
+- Missing declaration of etext in the A/UX version.
+- Some PCR root-finding problems.
+- Blacklisting was not 100% effective, because the plausible future
+  heap bounds were being miscalculated.
+- GC_realloc didn't handle out-of-memory correctly.
+- GC_base could return a nonzero value for addresses inside free blocks.
+- test.c wasn't really thread safe, and could erroneously report failure
+  in a multithreaded environment.  (The locking primitives need to be
+  replaced for other threads packages.)
+- GC_CONS was thoroughly broken.
+- On a SPARC with dynamic linking, signals stayed diabled while the
+  client code was running.
+  (Thanks to Manuel Serrano at INRIA for reporting the last two.)
+  
+  Version 2.4 added GC_free_space_divisor as a tuning knob, added
+  support for OS/2 and linux, and fixed the following bugs:
+- On machines with unaligned pointers (e.g. Sun 3), every 128th word could
+  fail to be considered for marking.
+- Dynamic_load.c erroneously added 4 bytes to the length of the data and
+  bss sections of the dynamic library.  This could result in a bad memory
+  reference if the actual length was a multiple of a page.  (Observed on
+  Sun 3.  Can probably also happen on a Sun 4.)
+  (Thanks to Robert Brazile for pointing out that the Sun 3 version
+  was broken.  Dynamic library handling is still broken on Sun 3s
+  under 4.1.1U1, but apparently not 4.1.1.  If you have such a machine,
+  use -Bstatic.)
+  
+  Version 2.5 fixed the following bugs:
+- Removed an explicit call to exit(1)
+- Fixed calls to GC_printf and GC_err_printf, so the correct number of
+  arguments are always supplied.  The OS/2 C compiler gets confused if
+  the number of actuals and the number of formals differ.  (ANSI C
+  doesn't require this to work.  The ANSI sanctioned way of doing things
+  causes too many compatibility problems.)
+  
+  Version 3.0  added generational/incremental collection and stubborn
+  objects.
+
+  Version 3.1 added the following features:
+- A workaround for a SunOS 4.X SPARC C compiler
+  misfeature that caused problems when the collector was turned into
+  a dynamic library.  
+- A fix for a bug in GC_base that could result in a memory fault.
+- A fix for a performance bug (and several other misfeatures) pointed
+  out by Dave Detlefs and Al Dosser.
+- Use of dirty bit information for static data under Solaris 2.X.
+- DEC Alpha/OSF1 support (thanks to Al Dosser).
+- Incremental collection on more platforms.
+- A more refined heap expansion policy.  Less space usage by default.
+- Various minor enhancements to reduce space usage, and to reduce
+  the amount of memory scanned by the collector.
+- Uncollectable allocation without per object overhead.
+- More conscientious handling of out-of-memory conditions.
+- Fixed a bug in debugging stubborn allocation.
+- Fixed a bug that resulted in occasional erroneous reporting of smashed
+  objects with debugging allocation.
+- Fixed bogus leak reports of size 4096 blocks with FIND_LEAK.
+
+  Version 3.2 fixed a serious and not entirely repeatable bug in
+  the incremental collector.  It appeared only when dirty bit info
+  on the roots was available, which is normally only under Solaris.
+  It also added GC_general_register_disappearing_link, and some
+  testing code.  Interface.c disappeared.
+
+  Version 3.3 fixes several bugs and adds new ports:
+- PCR-specific bugs.
+- Missing locking in GC_free, redundant FASTUNLOCK
+  in GC_malloc_stubborn, and 2 bugs in
+  GC_unregister_disappearing_link.
+  All of the above were pointed out by Neil Sharman
+  (neil@cs.mu.oz.au).
+- Common symbols allocated by the SunOS4.X dynamic loader
+  were not included in the root set.
+- Bug in GC_finalize (reported by Brian Beuning and Al Dosser)
+- Merged Amiga port from Jesper Peterson (untested)
+- Merged NeXT port from Thomas Funke (significantly
+  modified and untested)
+
+  Version 3.4:
+- Fixed a performance bug in GC_realloc.
+- Updated the amiga port.
+- Added NetBSD and 386BSD ports.
+- Added cord library.
+- Added trivial performance enhancement for
+  ALL_INTERIOR_POINTERS.  (Don't scan last word.)
+  
+  Version 3.5
+- Minor collections now mark from roots only once, if that
+  doesn't cause an excessive pause.
+- The stack clearing heuristic was refined to prevent anomalies
+  with very heavily recursive programs and sparse stacks.
+- Fixed a bug that prevented mark stack growth in some cases.
+  GC_objects_are_marked should be set to TRUE after a call
+  to GC_push_roots and as part of GC_push_marked, since
+  both can now set mark bits.  I think this is only a performance
+  bug, but I wouldn't bet on it.  It's certainly very hard to argue
+  that the old version was correct.
+- Fixed an incremental collection bug that prevented it from
+  working at all when HBLKSIZE != getpagesize()
+- Changed dynamic_loading.c to include gc_priv.h before testing
+  DYNAMIC_LOADING.  SunOS dynamic library scanning
+  must have been broken in 3.4.
+- Object size rounding now adapts to program behavior.
+- Added a workaround (provided by Manuel Serrano and
+  colleagues) to a long-standing SunOS 4.X (and 3.X?) ld bug
+  that I had incorrectly assumed to have been squished.
+  The collector was broken if the text segment size was within
+  32 bytes of a multiple of 8K bytes, and if the beginning of
+  the data segment contained interesting roots.  The workaround
+  assumes a demand-loadable executable.  The original may have
+  have "worked" in some other cases.
+- Added dynamic library support under IRIX5.
+- Added support for EMX under OS/2 (thanks to Ari Huttunen).
+  
+Version 3.6:
+- fixed a bug in the mark stack growth code that was introduced
+  in 3.4.
+- fixed Makefile to work around DEC AXP compiler tail recursion
+  bug.
+
+Version 3.7:
+- Added a workaround for an HP/UX compiler bug.
+- Fixed another stack clearing performance bug.  Reworked
+  that code once more.
+  
+Version 4.0:
+- Added support for Solaris threads (which was possible
+  only by reimplementing some fraction of Solaris threads,
+  since Sun doesn't currently make the thread debugging
+  interface available).
+- Added non-threads win32 and win32S support.
+- (Grudgingly, with suitable muttering of obscenities) renamed
+  files so that the collector distribution could live on a FAT
+  file system.  Files that are guaranteed to be useless on
+  a PC still have long names.  Gc_inline.h and gc_private.h
+  still exist, but now just include  gc_inl.h and gc_priv.h.
+- Fixed a really obscure bug in finalization that could cause
+  undetected mark stack overflows.  (I would be surprised if
+  any real code ever tickled this one.)
+- Changed finalization code to dynamically resize the hash
+  tables it maintains.  (This probably does not matter for well-
+  -written code.  It no doubt does for C++ code that overuses
+  destructors.)
+- Added typed allocation primitives.  Rewrote the marker to
+  accommodate them with more reasonable efficiency.  This
+  change should also speed up marking for GC_malloc allocated
+  objects a little.  See gc_typed.h for new primitives.
+- Improved debugging facilities slightly.  Allocation time
+  stack traces are now kept by default on SPARC/SUNOS4.
+  (Thanks to Scott Schwartz.)
+- Added better support for small heap applications.
+- Significantly extended cord package.  Fixed a bug in the
+  implementation of lazily read files.  Printf and friends now
+  have cord variants.  Cord traversals are a bit faster.
+- Made ALL_INTERIOR_POINTERS recognition the default.
+- Fixed de so that it can run in constant space, independent
+  of file size.  Added simple string searching to cords and de.
+- Added the Hull-Ellis C++ interface.
+- Added dynamic library support for OSF/1.
+  (Thanks to Al Dosser and Tim Bingham at DEC.)
+- Changed argument to GC_expand_hp to be expressed
+  in units of bytes instead of heap blocks.  (Necessary
+  since the heap block size now varies depending on
+  configuration.  The old version was never very clean.)
+- Added GC_get_heap_size().  The previous "equivalent"
+  was broken.
+- Restructured the Makefile a bit.  
+
+Since version 4.0:
+- Changed finalization implementation to guarantee that
+  finalization procedures are called outside of the allocation
+  lock, making direct use of the interface a little less dangerous.
+  MAY BREAK EXISTING CLIENTS that assume finalizers
+  are protected by a lock.  Since there seem to be few multithreaded
+  clients that use finalization, this is hopefully not much of
+  a problem.
+- Fixed a gross bug in CORD_prev.
+- Fixed a bug in blacklst.c that could result in unbounded
+  heap growth during startup on machines that do not clear
+  memory obtained from the OS (e.g. win32S).
+- Ported de editor to win32/win32S.  (This is now the only
+  version with a mouse-sensitive UI.)
+- Added GC_malloc_ignore_off_page to allocate large arrays
+  in the presence of ALL_INTERIOR_POINTERS.
+- Changed GC_call_with_alloc_lock to not disable signals in
+  the single-threaded case.
+- Reduced retry count in GC_collect_or_expand for garbage
+  collecting when out of memory.
+- Made uncollectable allocations bypass black-listing, as they
+  should.
+- Fixed a bug in typed_test in test.c that could cause (legitimate)
+  GC crashes.
+- Fixed some potential synchronization problems in finalize.c
+- Fixed a real locking problem in typd_mlc.c.
+- Worked around an AIX 3.2 compiler feature that results in
+  out of bounds memory references.
+- Partially worked around an IRIX5.2 beta problem (which may
+  or may not persist to the final release).
+- Fixed a bug in the heap integrity checking code that could
+  result in explicitly deallocated objects being identified as
+  smashed.  Fixed a bug in the dbg_mlc stack saving code
+  that caused old argument pointers to be considered live.
+- Fixed a bug in CORD_ncmp (and hence CORD_str).
+- Repaired the OS2 port, which had suffered from bit rot
+  in 4.0.  Worked around what appears to be CSet/2 V1.0
+  optimizer bug.
+- Fixed a Makefile bug for target "c++".
+
+Since version 4.1:
+- Multiple bug fixes/workarounds in the Solaris threads version.
+  (It occasionally failed to locate some register contents for
+  marking.  It also turns out that thr_suspend and friends are
+  unreliable in Solaris 2.3.  Dirty bit reads appear
+  to be unreliable under some weird 
+  circumstances.  My stack marking code
+  contained a serious performance bug.  The new code is
+  extremely defensive, and has not failed in several cpu
+  hours of testing.  But  no guarantees ...)
+- Added MacOS support (thanks to Patrick Beard.)
+- Fixed several syntactic bugs in gc_c++.h and friends.  (These
+  didn't bother g++, but did bother most other compilers.)
+  Fixed gc_c++.h finalization interface.  (It didn't.)
+- 64 bit alignment for allocated objects was not guaranteed in a
+  few cases in which it should have been.
+- Added GC_malloc_atomic_ignore_off_page.
+- Added GC_collect_a_little.
+- Added some prototypes to gc.h.
+- Some other minor bug fixes (notably in Makefile).
+- Fixed OS/2 / EMX port (thanks to Ari Huttunen).
+- Fixed AmigaDOS port. (thanks to Michel Schinz).
+- Fixed the DATASTART definition under Solaris.  There
+  was a 1 in 16K chance of the collector missing the first
+  64K of static data (and thus crashing).
+- Fixed some blatant anachronisms in the README file.
+- Fixed PCR-Makefile for upcoming PPCR release.
+
+Since version 4.2:
+- Fixed SPARC alignment problem with GC_DEBUG.
+- Fixed Solaris threads /proc workaround.  The real
+  problem was an interaction with mprotect.
+- Incorporated fix from Patrick Beard for gc_c++.h (now gc_cpp.h).
+- Slightly improved allocator space utilization by
+  fixing the GC_size_map mechanism.
+- Integrated some Sony News and MIPS RISCos 4.51
+  patches.  (Thanks to Nobuyuki Hikichi of
+  Software Research Associates, Inc. Japan)
+- Fixed HP_PA alignment problem.  (Thanks to
+  xjam@cork.cs.berkeley.edu.)
+- Added GC_same_obj and friends.  Changed GC_base
+  to return 0 for pointers past the end of large objects.
+  Improved GC_base performance with ALL_INTERIOR_POINTERS
+  on machines with a slow integer mod operation.
+  Added GC_PTR_ADD, GC_PTR_STORE, etc. to prepare
+  for preprocessor.
+- changed the default on most UNIX machines to be that
+  signals are not disabled during critical GC operations.
+  This is still ANSI-conforming, though somewhat dangerous
+  in the presence of signal handlers. But the performance
+  cost of the alternative is sometimes problematic.
+  Can be changed back with a minor Makefile edit.
+- renamed IS_STRING in gc.h, to CORD_IS_STRING, thus
+  following my own naming convention.  Added the function
+  CORD_to_const_char_star.
+- Fixed a gross bug in GC_finalize.  Symptom: occasional
+  address faults in that function.  (Thanks to Anselm
+  Baird-Smith (Anselm.BairdSmith@inria.fr)
+- Added port to ICL DRS6000 running DRS/NX.  Restructured
+  things a bit to factor out common code, and remove obsolete
+  code.  Collector should now run under SUNOS5 with either
+  mprotect or /proc dirty bits.  (Thanks to Douglas Steel
+  (doug@wg.icl.co.uk)).
+- More bug fixes and workarounds for Solaris 2.X.  (These were
+  mostly related to putting the collector in a dynamic library,
+  which didn't really work before.  Also SOLARIS_THREADS
+  didn't interact well with dl_open.)  Thanks to btlewis@eng.sun.com.
+- Fixed a serious performance bug on the DEC Alpha.  The text
+  segment was getting registered as part of the root set.
+  (Amazingly, the result was still fast enough that the bug
+  was not conspicuous.) The fix works on OSF/1, version 1.3.
+  Hopefully it also works on other versions of OSF/1 ...
+- Fixed a bug in GC_clear_roots.
+- Fixed a bug in GC_generic_malloc_words_small that broke
+  gc_inl.h.  (Reported by Antoine de Maricourt.  I broke it
+  in trying to tweak the Mac port.) 
+- Fixed some problems with cord/de under Linux.
+- Fixed some cord problems, notably with CORD_riter4.
+- Added DG/UX port.
+  Thanks to Ben A. Mesander (ben@piglet.cr.usgs.gov)
+- Added finalization registration routines with weaker ordering
+  constraints.  (This is necessary for C++ finalization with
+  multiple inheritance, since the compiler often adds self-cycles.)
+- Filled the holes in the SCO port. (Thanks to Michael Arnoldus
+  <chime@proinf.dk>.)
+- John Ellis' additions to the C++ support:  From John:
+
+* I completely rewrote the documentation in the interface gc_c++.h
+(later renamed gc_cpp.h).  I've tried to make it both clearer and more
+precise.
+
+* The definition of accessibility now ignores pointers from an
+finalizable object (an object with a clean-up function) to itself.
+This allows objects with virtual base classes to be finalizable by the
+collector.  Compilers typically implement virtual base classes using
+pointers from an object to itself, which under the old definition of
+accessibility prevented objects with virtual base classes from ever
+being collected or finalized.
+
+* gc_cleanup now includes gc as a virtual base.  This was enabled by
+the change in the definition of accessibility.
+
+* I added support for operator new[].  Since most (all?) compilers
+don't yet support operator new[], it is conditionalized on
+-DOPERATOR_NEW_ARRAY.  The code is untested, but its trivial and looks
+correct.
+
+* The test program test_gc_c++ (later renamed test_cpp.cc)
+tries to test for the C++-specific functionality not tested by the
+other programs.
+- Added <unistd.h> include to misc.c.  (Needed for ppcr.)
+- Added PowerMac port. (Thanks to Patrick Beard again.)
+- Fixed "srcdir"-related Makefile problems.  Changed things so
+  that all externally visible include files always appear in the
+  include subdirectory of the source.  Made gc.h directly
+  includable from C++ code.  (These were at Per
+  Bothner's suggestion.)
+- Changed Intel code to also mark from ebp (Kevin Warne's
+  suggestion).
+- Renamed C++ related files so they could live in a FAT
+  file system. (Charles Fiterman's suggestion.)
+- Changed Windows NT Makefile to include C++ support in
+  gc.lib.  Added C++ test as Makefile target.
+  
+Since version 4.3:
+ - ASM_CLEAR_CODE was erroneously defined for HP
+   PA machines, resulting in a compile error.
+ - Fixed OS/2 Makefile to create a library.  (Thanks to
+   Mark Boulter (mboulter@vnet.ibm.com)).
+ - Gc_cleanup objects didn't work if they were created on
+   the stack.  Fixed.
+ - One copy of Gc_cpp.h in the distribution was out of 
+   synch, and failed to document some known compiler
+   problems with explicit destructor invocation.  Partially
+   fixed.  There are probably other compilers on which
+   gc_cleanup is miscompiled.
+ - Fixed Makefile to pass C compiler flags to C++ compiler.
+ - Added Mac fixes.
+ - Fixed os_dep.c to work around what appears to be
+   a new and different VirtualQuery bug under newer
+   versions of win32S.
+ - GC_non_gc_bytes was not correctly maintained by
+   GC_free.  Fixed.  Thanks to James Clark (jjc@jclark.com).
+ - Added GC_set_max_heap_size.
+ - Changed allocation code to ignore blacklisting if it is preventing
+   use of a very large block of memory.  This has the advantage
+   that naive code allocating very large objects is much more
+   likely to work.  The downside is you might no
+   longer find out that such code should really use
+   GC_malloc_ignore_off_page.
+ - Changed GC_printf under win32 to close and reopen the file
+   between calls.  FAT file systems otherwise make the log file
+   useless for debugging.
+ - Added GC_try_to_collect and GC_get_bytes_since_gc.  These
+   allow starting an abortable collection during idle times. 
+   This facility does not require special OS support.  (Thanks to
+   Michael Spertus of Geodesic Systems for suggesting this.  It was
+   actually an easy addition.  Kumar Srikantan previously added a similar
+   facility to a now ancient version of the collector.  At the time
+   this was much harder, and the result was less convincing.)
+ - Added some support for the Borland development environment.  (Thanks
+   to John Ellis and Michael Spertus.)
+ - Removed a misfeature from checksums.c that caused unexpected 
+   heap growth.  (Thanks to Scott Schwartz.)
+ - Changed finalize.c to call WARN if it encounters a finalization cycle.
+   WARN is defined in gc_priv.h to write a message, usually to stdout.
+   In many environments, this may be inappropriate.
+ - Renamed NO_PARAMS in gc.h to GC_NO_PARAMS, thus adhering to my own
+   naming convention.
+ - Added GC_set_warn_proc to intercept warnings.
+ - Fixed Amiga port. (Thanks to Michel Schinz (schinz@alphanet.ch).)
+ - Fixed a bug in mark.c that could result in an access to unmapped
+   memory from GC_mark_from_mark_stack on machines with unaligned
+   pointers.
+ - Fixed a win32 specific performance bug that could result in scanning of
+   objects allocated with the system malloc.
+ - Added REDIRECT_MALLOC.
+
+Since version 4.4:
+ - Fixed many minor and one major README bugs. (Thanks to Franklin Chen
+   (chen@adi.com) for pointing out many of them.)
+ - Fixed ALPHA/OSF/1 dynamic library support. (Thanks to Jonathan Bachrach
+   (jonathan@harlequin.com)).
+ - Added incremental GC support (MPROTECT_VDB) for Linux (with some
+   help from Bruno Haible).
+ - Altered SPARC recognition tests in gc.h and config.h (mostly as
+   suggested by Fergus Henderson).
+ - Added basic incremental GC support for win32, as implemented by
+   Windows NT and Windows 95.  GC_enable_incremental is a noop
+   under win32s, which doesn't implement enough of the VM interface.
+ - Added -DLARGE_CONFIG.
+ - Fixed GC_..._ignore_off_page to also function without
+   -DALL_INTERIOR_POINTERS.
+ - (Hopefully) fixed RS/6000 port.  (Only the test was broken.)
+ - Fixed a performance bug in the nonincremental collector running
+   on machines supporting incremental collection with MPROTECT_VDB
+   (e.g. SunOS 4, DEC AXP).  This turned into a correctness bug under
+   win32s with win32 incremental collection.  (Not all memory protection
+   was disabled.)
+ - Fixed some ppcr related bit rot.
+ - Caused dynamic libraries to be unregistered before reregistering.
+   The old way turned out to be a performance bug on some machines.
+ - GC_root_size was not properly maintained under MSWIN32.
+ - Added -DNO_DEBUGGING and GC_dump.
+ - Fixed a couple of bugs arising with SOLARIS_THREADS +
+   REDIRECT_MALLOC.
+ - Added NetBSD/M68K port.  (Thanks to Peter Seebach
+   <seebs@taniemarie.solon.com>.)
+ - Fixed a serious realloc bug.  For certain object sizes, the collector
+   wouldn't scan the expanded part of the object.  (Thanks to Clay Spence
+   (cds@peanut.sarnoff.com) for noticing the problem, and helping me to
+   track it down.)
+   
+Since version 4.5:
+ - Added Linux ELF support.  (Thanks to Arrigo Triulzi <arrigo@ic.ac.uk>.)
+ - GC_base crashed if it was called before any other GC_ routines.
+   This could happen if a gc_cleanup object was allocated outside the heap
+   before any heap allocation.
+ - The heap expansion heuristic was not stable if all objects had finalization
+   enabled.  Fixed finalize.c to count memory in finalization queue and
+   avoid explicit deallocation.  Changed alloc.c to also consider this count.
+   (This is still not recommended.  It's expensive if nothing else.)  Thanks
+   to John Ellis for pointing this out.
+ - GC_malloc_uncollectable(0) was broken.  Thanks to Phong Vo for pointing
+   this out.
+ - The collector didn't compile under Linux 1.3.X.  (Thanks to Fred Gilham for
+   pointing this out.)  The current workaround is ugly, but expected to be
+   temporary.
+ - Fixed a formatting problem for SPARC stack traces.
+ - Fixed some '=='s in os_dep.c that should have been assignments.
+   Fortunately these were in code that should never be executed anyway.
+   (Thanks to Fergus Henderson.)
+ - Fixed the heap block allocator to only drop blacklisted blocks in small
+   chunks.  Made BL_LIMIT self adjusting.  (Both of these were in response
+   to heap growth observed by Paul Graham.)
+ - Fixed the Metrowerks/68K Mac code to also mark from a6.  (Thanks
+   to Patrick Beard.)
+ - Significantly updated README.debugging.
+ - Fixed some problems with longjmps out of signal handlers, especially under
+   Solaris.  Added a workaround for the fact that siglongjmp doesn't appear to
+   do the right thing with -lthread under Solaris.
+ - Added MSDOS/djgpp port.  (Thanks to Mitch Harris  (maharri@uiuc.edu).)
+ - Added "make reserved_namespace" and "make user_namespace".  The
+   first renames ALL "GC_xxx" identifiers as "_GC_xxx".  The second is the
+   inverse transformation.  Note that doing this is guaranteed to break all
+   clients written for the other names.
+ - descriptor field for kind NORMAL in GC_obj_kinds with ADD_BYTE_AT_END
+   defined should be -ALIGNMENT not WORDS_TO_BYTES(-1).  This is
+   a serious bug on machines with pointer alignment of less than a word.
+ - GC_ignore_self_finalize_mark_proc didn't handle pointers to very near the
+   end of the object correctly.  Caused failures of the C++ test on a DEC Alpha
+   with g++.
+ - gc_inl.h still had problems.  Partially fixed.  Added warnings at the
+   beginning to hopefully specify the remaining dangers.
+ - Added DATAEND definition to config.h.
+ - Fixed some of the .h file organization.  Fixed "make floppy".
+ 
+Since version 4.6:
+ - Fixed some compilation problems with -DCHECKSUMS (thanks to Ian Searle)
+ - Updated some Mac specific files to synchronize with Patrick Beard.
+ - Fixed a serious bug for machines with non-word-aligned pointers.
+   (Thanks to Patrick Beard for pointing out the problem.  The collector
+   should fail almost any conceivable test immediately on such machines.)
+
+Since version 4.7:
+ - Changed a "comment" in a MacOS specific part of mach-dep.c that caused
+   gcc to fail on other platforms.
+
+Since version 4.8
+ - More README.debugging fixes.
+ - Objects ready for finalization, but not finalized in the same GC
+   cycle, could be prematurely collected.  This occasionally happened
+   in test_cpp.
+ - Too little memory was obtained from the system for very large
+   objects.  That could cause a heap explosion if these objects were
+   not contiguous (e.g. under PCR), and too much of them was blacklisted.
+ - Due to an improper initialization, the collector was too hesitant to
+   allocate blacklisted objects immediately after system startup.
+ - Moved GC_arrays from the data into the bss segment by not explicitly
+   initializing it to zero.  This significantly
+   reduces the size of executables, and probably avoids some disk accesses
+   on program startup.  It's conceivable that it might break a port that I
+   didn't test.
+ - Fixed EMX_MAKEFILE to reflect the gc_c++.h to gc_cpp.h renaming which
+   occurred a while ago.
+
+Since 4.9:
+ - Fixed a typo around a call to GC_collect_or_expand in alloc.c.  It broke
+   handling of out of memory.  (Thanks to Patrick Beard for noticing.)
+
+Since 4.10:
+ - Rationalized (hopefully) GC_try_to_collect in an incremental collection
+   environment.  It appeared to not handle a call while a collection was in
+   progress, and was otherwise too conservative.
+ - Merged GC_reclaim_or_delete_all into GC_reclaim_all to get rid of some
+   code.
+ - Added Patrick Beard's Mac fixes, with substantial completely untested
+   modifications.
+ - Fixed the MPROTECT_VDB code to deal with large pages and imprecise
+   fault addresses (as on an UltraSPARC running Solaris 2.5).  Note that this
+   was not a problem in the default configuration, which uses PROC_VDB.
+ - The DEC Alpha assembly code needed to restore $gp between calls.
+   Thanks to Fergus Henderson for tracking this down and supplying a
+   patch.
+ - The write command for "de" was completely broken for large files.
+   I used the easiest portable fix, which involved changing the semantics
+   so that f.new is written instead of overwriting f.  That's safer anyway.
+ - Added README.solaris2 with a discussion of the possible problems of
+   mixing the collector's sbrk allocation with malloc/realloc.
+ - Changed the data segment starting address for SGI machines.  The
+   old code failed under IRIX6.
+ - Required double word alignment for MIPS.
+ - Various minor fixes to remove warnings.
+ - Attempted to fix some Solaris threads problems reported by Zhiying Chen.
+   In particular, the collector could try to fork a thread with the
+   world stopped as part of GC_thr_init.  It also failed to deal with
+   the case in which the original thread terminated before the whole
+   process did.
+ - Added -DNO_EXECUTE_PERMISSION.  This has a major performance impact
+   on the incremental collector under Irix, and perhaps under other
+   operating systems.
+ - Added some code to support allocating the heap with mmap.  This may
+   be preferable under some circumstances.
+ - Integrated dynamic library support for HP.
+   (Thanks to Knut Tvedten <knuttv@ifi.uio.no>.)
+ - Integrated James Clark's win32 threads support, and made a number
+   of changes to it, many of which were suggested by Pontus Rydin.
+   This is still not 100% solid.
+ - Integrated Alistair Crooks' support for UTS4 running on an Amdahl
+   370-class machine.
+ - Fixed a serious bug in explicitly typed allocation.  Objects requiring
+   large descriptors where handled in a way that usually resulted in
+   a segmentation fault in the marker.  (Thanks to Jeremy Fitzhardinge
+   for helping to track this down.)
+ - Added partial support for GNU win32 development.  (Thanks to Fergus
+   Henderson.)
+ - Added optional support for Java-style finalization semantics.  (Thanks
+   to Patrick Bridges.)  This is recommended only for Java implementations.
+ - GC_malloc_uncollectable faulted instead of returning 0 when out of
+   memory.  (Thanks to dan@math.uiuc.edu for noticing.)
+ - Calls to GC_base before the collector was initialized failed on a
+   DEC Alpha.  (Thanks to Matthew Flatt.)
+ - Added base pointer checking to GC_REGISTER_FINALIZER in debugging
+   mode, at the suggestion of Jeremy Fitzhardinge.
+ - GC_debug_realloc failed for uncollectable objects.  (Thanks to
+   Jeremy Fitzhardinge.)
+ - Explicitly typed allocation could crash if it ran out of memory.
+   (Thanks to Jeremy Fitzhardinge.)
+ - Added minimal support for a DEC Alpha running Linux.
+ - Fixed a problem with allocation of objects whose size overflowed
+   ptrdiff_t.  (This now fails unconditionally, as it should.)
+ - Added the beginning of Irix pthread support.
+ - Integrated Xiaokun Zhu's fixes for djgpp 2.01.
+ - Added SGI-style STL allocator support (gc_alloc.h).
+ - Fixed a serious bug in README.solaris2.  Multithreaded programs must include
+   gc.h with SOLARIS_THREADS defined.
+ - Changed GC_free so it actually deallocates uncollectable objects.
+   (Thanks to Peter Chubb for pointing out the problem.)
+ - Added Linux ELF support for dynamic libararies.  (Thanks again to
+   Patrick Bridges.)
+ - Changed the Borland cc configuration so that the assembler is not
+   required.
+ - Fixed a bug in the C++ test that caused it to fail in 64-bit
+   environments.
+
+Since 4.11:
+ - Fixed ElfW definition in dyn_load.c. (Thanks to Fergus Henderson.)
+   This prevented the dynamic library support from compiling on some
+   older ELF Linux systems.
+ - Fixed UTS4 port (which I apparently mangled during the integration)
+   (Thanks to again to Alistair Crooks.)
+ - "Make C++" failed on Suns with SC4.0, due to a problem with "bool".
+   Fixed in gc_priv.h.
+ - Added more pieces for GNU win32.  (Thanks to Timothy N. Newsham.)
+   The current state of things should suffice for at least some
+   applications.
+ - Changed the out of memory retry count handling as suggested by
+   Kenjiro Taura.  (This matters only if GC_max_retries > 0, which
+   is no longer the default.)
+ - If a /proc read failed repeatedly, GC_written_pages was not updated
+   correctly.  (Thanks to Peter Chubb for diagnosing this.)
+ - Under unlikely circumstances, the allocator could infinite loop in
+   an out of memory situation.  (Thanks again to Kenjiro Taura for
+   identifying the problem and supplying a fix.)
+ - Fixed a syntactic error in the DJGPP code.  (Thanks to Fergus
+   Henderson for finding this by inspection.)  Also fixed a test program
+   problem with DJGPP (Thanks to Peter Monks.)
+ - Atomic uncollectable objects were not treated correctly by the
+   incremental collector.  This resulted in weird log statistics and
+   occasional performance problems.  (Thanks to Peter Chubb for pointing
+   this out.)
+ - Fixed some problems resulting from compilers that dont define
+   __STDC__.  In this case void * and char * were used inconsistently
+   in some cases.  (Void * should not have been used at all.  If
+   you have an ANSI superset compiler that does not define __STDC__,
+   please compile with -D__STDC__=0. Thanks to Manuel Serrano and others
+   for pointing out the problem.)
+ - Fixed a compilation problem on Irix with -n32 and -DIRIX_THREADS.
+   Also fixed some other IRIX_THREADS problems which may or may not have
+   had observable symptoms.
+ - Fixed an HP PA compilation problem in dyn_load.c.  (Thanks to
+   Philippe Queinnec.)
+ - SEGV fault handlers sometimes did not get reset correctly.  (Thanks
+   to David Pickens.)
+ - Added a fix for SOLARIS_THREADS on Intel.  (Thanks again to David
+   Pickens.)  This probably needs more work to become functional.
+ - Fixed struct sigcontext_struct in os_dep.c for compilation under
+   Linux 2.1.X.	(Thanks to Fergus Henderson.)
+ - Changed the DJGPP STACKBOTTOM and DATASTART values to those suggested
+   by Kristian Kristensen.  These may still not be right, but it is
+   it is likely to work more often than what was there before.  They may
+   even be exactly right.
+ - Added a #include <string.h> to test_cpp.cc.  This appears to help
+   with HP/UX and gcc.  (Thanks to assar@sics.se.)
+ - Version 4.11 failed to run in incremental mode on recent 64-bit Irix
+   kernels.  This was a problem related to page unaligned heap segments.
+   Changed the code to page align heap sections on all platforms.
+   (I had mistakenly identified this as a kernel problem earlier.
+   It was not.)
+ - Version 4.11 did not make allocated storage executable, except on
+   one or two platforms, due to a bug in a #if test.  (Thanks to Dave
+   Grove for pointing this out.)
+ - Added sparc_sunos4_mach_dep.s to support Sun's compilers under SunOS4.
+ - Added GC_exclude_static_roots.
+ - Fixed the object size mapping algorithm.  This shouldn't matter,
+   but the old code was ugly.
+ - Heap checking code could die if one of the allocated objects was
+   larger than its base address.  (Unsigned underflow problem.  Thanks
+   to Clay Spence for isolating the problem.)
+ - Added RS6000 (AIX) dynamic library support and fixed STACK_BOTTOM.
+   (Thanks to Fred Stearns.)
+ - Added Fergus Henderson's patches for improved robustness with large
+   heaps and lots of blacklisting.
+ - Added Peter Chubb's changes to support Solaris Pthreads, to support
+   MMAP allocation in Solaris, to allow Solaris to find dynamic libraries
+   through /proc, to add malloc_typed_ignore_off_page, and a few other
+   minor features and bug fixes.
+ - The Solaris 2 port should not use sbrk.  I received confirmation from
+   Sun that the use of sbrk and malloc in the same program is not
+   supported.  The collector now defines USE_MMAP by default on Solaris.
+ - Replaced the djgpp makefile with Gary Leavens' version.
+ - Fixed MSWIN32 detection test.
+ - Added Fergus Henderson's patches to allow putting the collector into
+   a DLL under GNU win32.
+ - Added Ivan V. Demakov's port to Watcom C on X86.
+ - Added Ian Piumarta's Linux/PowerPC port.
+ - On Brian Burton's suggestion added PointerFreeGC to the placement
+   options in gc_cpp.h.  This is of course unsafe, and may be controversial.
+   On the other hand, it seems to be needed often enough that it's worth
+   adding as a standard facility.
+
+Since 4.12:
+ - Fixed a crucial bug in the Watcom port.  There was a redundant decl
+   of GC_push_one in gc_priv.h.
+ - Added FINALIZE_ON_DEMAND.
+ - Fixed some pre-ANSI cc problems in test.c.
+ - Removed getpagesize() use for Solaris.  It seems to be missing in one
+   or two versions.
+ - Fixed bool handling for SPARCCompiler version 4.2.
+ - Fixed some files in include that had gotten unlinked from the main
+   copy.
+ - Some RS/6000 fixes (missing casts).  Thanks to Toralf Foerster.
+ - Fixed several problems in GC_debug_realloc, affecting mostly the
+   FIND_LEAK case.
+ - GC_exclude_static_roots contained a buggy unsigned comparison to
+   terminate a loop.  (Thanks to Wilson Ho.)
+ - CORD_str failed if the substring occurred at the last possible position.
+   (Only affects cord users.)
+ - Fixed Linux code to deal with RedHat 5.0 and integrated Peter Bigot's
+   os_dep.c code for dealing with various Linux versions.
+ - Added workaround for Irix pthreads sigaction bug and possible signal
+   misdirection problems.
+Since alpha1:
+ - Changed RS6000 STACKBOTTOM.
+ - Integrated Patrick Beard's Mac changes.
+ - Alpha1 didn't compile on Irix m.n, m < 6.
+ - Replaced Makefile.dj with a new one from Gary Leavens.
+ - Added Andrew Stitcher's changes to support SCO OpenServer.
+ - Added PRINT_BLACK_LIST, to allow debugging of high densities of false
+   pointers.
+ - Added code to debug allocator to keep track of return address
+   in GC_malloc caller, thus giving a bit more context.
+ - Changed default behavior of large block allocator to more
+   aggressively avoid fragmentation.  This is likely to slow down the
+   collector when it succeeds at reducing space cost.
+ - Integrated Fergus Henderson's CYGWIN32 changes.  They are untested,
+   but needed for newer versions.
+ - USE_MMAP had some serious bugs.  This caused the collector to fail
+   consistently on Solaris with -DSMALL_CONFIG.
+ - Added Linux threads support, thanks largely to Fergus Henderson.
+Since alpha2:
+ - Fixed more Linux threads problems.
+ - Changed default GC_free_space_divisor to 3 with new large block allocation.
+   (Thanks to Matthew Flatt for some measurements that suggest the old
+   value sometimes favors space too much over time.)
+ - More CYGWIN32 fixes.
+ - Integrated Tyson-Dowd's Linux-M68K port.
+ - Minor HP PA and DEC UNIX fixes from Fergus Henderson.
+ - Integrated Christoffe Raffali's Linux-SPARC changes.
+ - Allowed for one more GC fixup iteration after a full GC in incremental
+   mode.  Some quick measurements suggested that this significantly
+   reduces pause times even with smaller GC_RATE values.
+ - Moved some more GC data structures into GC_arrays.  This decreases
+   pause times and GC overhead, but makes debugging slightly less convenient.
+ - Fixed namespace pollution problem ("excl_table").
+ - Made GC_incremental a constant for -DSMALL_CONFIG, hopefully shrinking
+   that slightly.
+ - Added some win32 threads fixes.
+ - Integrated Ivan Demakov and David Stes' Watcom fixes.
+ - Various other minor fixes contributed by many people.
+ - Renamed config.h to gcconfig.h, since config.h tends to be used for
+   many other things.
+ - Integrated Matthew Flatt's support for 68K MacOS "far globals".
+ - Fixed up some of the dynamic library Makefile targets for consistency
+   across platforms.
+ - Fixed a USE_MMAP typo that caused out-of-memory handling to fail
+   on Solaris.
+ - Added code to test.c to test thread creation a bit more.
+ - Integrated GC_win32_free_heap, as suggested by Ivan Demakov.
+ - Fixed Solaris 2.7 stack base finding problem.  (This may actually
+   have been done in an earlier alpha release.)
+Since alpha3:
+ - Fixed MSWIN32 recognition test, which interfered with cygwin.
+ - Removed unnecessary gc_watcom.asm from distribution.  Removed
+   some obsolete README.win32 text.
+ - Added Alpha Linux incremental GC support.  (Thanks to Philipp Tomsich
+   for code for retrieving the fault address in a signal handler.)
+   Changed Linux signal handler context argument to be a pointer.
+ - Took care of some new warnings generated by the 7.3 SGI compiler.
+ - Integrated Phillip Musumeci's FreeBSD/ELF fixes.
+ - -DIRIX_THREADS was broken with the -o32 ABI (typo in gc_priv.h>
+
+Since 4.13:
+ - Fixed GC_print_source_ptr to not use a prototype.
+ - generalized CYGWIN test.
+ - gc::new did the wrong thing with PointerFreeGC placement.
+   (Thanks to Rauli Ruohonen.)
+ - In the ALL_INTERIOR_POINTERS (default) case, some callee-save register
+   values could fail to be scanned if the register was saved and
+   reused in a GC frame.  This showed up in verbose mode with gctest
+   compiled with an unreleased SGI compiler.  I vaguely recall an old
+   bug report that may have been related.  The bug was probably quite old.
+   (The problem was that the stack scanning could be deferred until
+   after the relevant frame was overwritten, and the new save location
+   might be outside the scanned area.  Fixed by more eager stack scanning.)
+ - PRINT_BLACK_LIST had some problems.  A few source addresses were garbage.
+ - Replaced Makefile.dj and added -I flags to cord make targets.
+   (Thanks to Gary Leavens.)
+ - GC_try_to_collect was broken with the nonincremental collector.
+ - gc_cleanup destructors could pass the wrong address to
+   GC_register_finalizer_ignore_self in the presence of multiple
+   inheritance.  (Thanks to Darrell Schiebel.)
+ - Changed PowerPC Linux stack finding code.
+
+Since 4.14alpha1
+ - -DSMALL_CONFIG did not work reliably with large (> 4K) pages.
+   Recycling the mark stack during expansion could result in a size
+   zero heap segment, which confused things.  (This was probably also an
+   issue with the normal config and huge pages.)
+ - Did more work to make sure that callee-save registers were scanned
+   completely, even with the setjmp-based code.  Added USE_GENERIC_PUSH_REGS
+   macro to facilitate testing on machines I have access to.
+ - Added code to explicitly push register contents for win32 threads.
+   This seems to be necessary.  (Thanks to Pierre de Rop.)
+
+Since 4.14alpha2
+ - changed STACKBOTTOM for DJGPP (Thanks to Salvador Eduardo Tropea).
+ 
+Since 4.14
+ - Reworked large block allocator.  Now uses multiple doubly linked free
+   lists to approximate best fit.
+ - Changed heap expansion heuristic.  Entirely free blocks are no longer
+   counted towards the heap size.  This seems to have a major impact on
+   heap size stability; the old version could expand the heap way too
+   much in the presence of large block fragmentation.
+ - added -DGC_ASSERTIONS and some simple assertions inside the collector.
+   This is mainlyt for collector debugging.
+ - added -DUSE_MUNMAP to allow the heap to shrink.  Suupported on only
+   a few UNIX-like platforms for now.
+ - added GC_dump_regions() for debugging of fragmentation issues.
+ - Changed PowerPC pointer alignment under Linux to 4.  (This needs
+   checking by someone who has one.  The suggestions came to me via a
+   rather circuitous path.)
+ - Changed the Linux/Alpha port to walk the data segment backwards until
+   it encounters a SIGSEGV.  The old way to find the start of the data
+   segment broke with a recent release.
+ - cordxtra.c needed to call GC_REGISTER_FINALIZER instead of
+   GC_register_finalizer, so that it would continue to work with GC_DEBUG.
+ - allochblk sometimes cleared the wrong block for debugging purposes
+   when it dropped blacklisted blocks.  This could result in spurious
+   error reports with GC_DEBUG.
+ - added MACOS X Server support.  (Thanks to Andrew Stone.)
+ - Changed the Solaris threads code to ignore stack limits > 8 MB with
+   a warning.  Empirically, it is not safe to access arbitrary pages
+   in such large stacks.  And the dirty bit implementation does not
+   guarantee that none of them will be accessed.
+ - Integrated Martin Tauchmann's Amiga changes.
+ - Integrated James Dominy's OpenBSD/SPARC port.
+
+Since 5.0alpha1
+ - Fixed bugs introduced in alpha1 (OpenBSD & large block initialization).
+ - Added -DKEEP_BACK_PTRS and backptr.h interface.  (The implementation
+   idea came from Al Demers.)
+
+Since 5.0alpha2
+ - Added some highly incomplete code to support a copied young generation.
+   Comments on nursery.h are appreciated.
+ - Changed -DFIND_LEAK, -DJAVA_FINALIZATION, and -DFINALIZE_ON_DEMAND,
+   so the same effect could be obtained with a runtime switch.   This is
+   a step towards standardizing on a single dynamic GC library.
+ - Significantly changed the way leak detection is handled, as a consequence
+   of the above.
+
+Since 5.0 alpha3
+ - Added protection fault handling patch for Linux/M68K from Fergus
+   Henderson and Roman Hodek.
+ - Removed the tests for SGI_SOURCE in new_gc_alloc.h.  This was causing that
+   interface to fail on nonSGI platforms.
+ - Changed the Linux stack finding code to use /proc, after changing it
+   to use HEURISTIC1.  (Thanks to David Mossberger for pointing out the
+   /proc hook.)
+ - Added HP/UX incremental GC support and HP/UX 11 thread support.
+   Thread support is currently still flakey.
+ - Added basic Linux/IA64 support.
+ - Integrated Anthony Green's PicoJava support.
+ - Integrated Scott Ananian's StrongARM/NetBSD support.
+ - Fixed some fairly serious performance bugs in the incremental
+   collector.  These have probably been there essentially forever.
+   (Mark bits were sometimes set before scanning dirty pages.
+   The reclaim phase unnecessarily dirtied full small object pages.)
+ - Changed the reclaim phase to ignore nearly full pages to avoid
+   touching them.
+ - Limited GC_black_list_spacing to roughly the heap growth increment.
+ - Changed full collection triggering heuristic to decrease full GC
+   frequency by default, but to explicitly trigger full GCs during
+   heap growth.  This doesn't always improve things, but on average it's
+   probably a win.
+ - GC_debug_free(0, ...) failed.  Thanks to Fergus Henderson for the
+   bug report and fix.
+
+Since 5.0 alpha4
+ - GC_malloc_explicitly_typed and friends sometimes failed to
+   initialize first word.
+ - Added allocation routines and support in the marker for mark descriptors
+   in a type structure referenced by the first word of an object.  This was
+   introduced to support gcj, but hopefully in a way that makes it
+   generically useful.
+ - Added GC_requested_heapsize, and inhibited collections in nonincremental
+   mode if the actual used heap size is less than what was explicitly
+   requested.
+ - The Solaris pthreads version of GC_pthread_create didn't handle a NULL
+   attribute pointer.  Solaris thread support used the wrong default thread
+   stack size.  (Thanks to Melissa O'Neill for the patch.)
+ - Changed PUSH_CONTENTS macro to no longer modify first parameter.
+   This usually doesn't matter, but it was certainly an accident waiting
+   to happen ...
+ - Added GC_register_finalizer_no_order and friends to gc.h.  They're
+   needed by Java implementations.
+ - Integrated a fix for a win32 deadlock resulting from clock() calling
+   malloc.  (Thanks to Chris Dodd.)
+ - Integrated Hiroshi Kawashima's port to Linux/MIPS.  This was designed
+   for a handheld platform, and may or may not be sufficient for other
+   machines.
+ - Fixed a va_arg problem with the %c specifier in cordprnt.c.  It appears
+   that this was always broken, but recent versions of gcc are the first to
+   report the (statically detectable) bug.
+ - Added an attempt at a more general solution to dlopen races/deadlocks.
+   GC_dlopen now temporarily disables collection.  Still not ideal, but ...
+ - Added -DUSE_I686_PREFETCH, -DUSE_3DNOW_PREFETCH, and support for IA64
+   prefetch instructions.  May improve performance measurably, but I'm not
+   sure the code will run correctly on processors that don't support the
+   instruction.  Won't build except with very recent gcc.
+ - Added caching for header lookups in the marker.  This seems to result
+   in a barely measurable performance gain.  Added support for interleaved
+   lookups of two pointers, but unconfigured that since the performance
+   gain is currently near zero, and it adds to code size.
+ - Changed Linux DATA_START definition to check both data_start and
+   __data_start, since nothing else seems to be portable.
+ - Added -DUSE_LD_WRAP to optionally take advantage of the GNU ld function
+   wrapping mechanism.  Probably currently useful only on Linux.
+ - Moved some variables for the scratch allocator into GC_arrays, on
+   Martin Hirzel's suggestion.
+ - Fixed a win32 threads bug that caused the collector to not look for
+   interior pointers from one of the thread stacks without
+   ALL_INTERIOR_POINTERS.  (Thanks to Jeff Sturm.)
+ - Added Mingw32 support.  (Thanks again to Jeff Sturm for the patch.)
+ - Changed the alpha port to use the generic register scanning code instead
+   of alpha_mach_dep.s.  Alpha_mach_dep.s doesn't look for pointers in fp
+   registers, but gcc sometimes spills pointers there.  (Thanks to Manuel
+   Serrano for helping me debug this by email.)  Changed the IA64 code to
+   do something similar for similar reasons.
+
+[5.0alpha5 doesn't really exist, but it may have escaped.]
+
+Since 5.0alpha6:
+ - -DREDIRECT_MALLOC was broken in alpha6. Fixed.
+ - Cleaned up gc_ccp.h slightly, thus also causing the HP C++ compiler to
+   accept it.
+ - Removed accidental reference to dbg_mlc.c, which caused dbg_mlc.o to be
+   linked into every executable.
+ - Added PREFETCH to bitmap marker.  Changed it to use the header cache.
+ - GC_push_marked sometimes pushed one object too many, resulting in a
+   segmentation fault in GC_mark_from_mark_stack.  This was probably an old
+   bug.  It finally showed up in gctest on win32.
+ - Gc_priv.h erroneously #defined GC_incremental to be TRUE instead of FALSE
+   when SMALL_CONFIG was defined.  This was no doubt a major performance bug for
+   the default win32 configuration.
+ - Removed -DSMALL_CONFIG from NT_MAKEFILE.  It seemed like an anchronism now
+   that the average PC has 64MB or so.
+ - Integrated Bryce McKinley's patches for linux threads and dynamic loading
+   from the libgcj tree.  Turned on dynamic loading support for Linux/PPC.
+ - Changed the stack finding code to use environ on HP/UX.  (Thanks
+   to Gustavo Rodriguez-Rivera for the suggestion.)  This should probably
+   be done on other platforms, too.  Since I can't test those, that'll
+   wait until after 5.0.
+
+Since 5.0alpha7:
+ - Fixed threadlibs.c for linux threads.  -DUSE_LD_WRAP was broken and
+   -ldl was omitted.  Fixed Linux stack finding code to handle
+   -DUSE_LD_WRAP correctly.
+ - Added MSWIN32 exception handler around marker, so that the collector
+   can recover from root segments that are unmapped during the collection.
+   This caused occasional failures under Windows 98, and may also be
+   an issue under Windows NT/2000.
+
+Since 5.0
+ - Fixed a gc.h header bug which showed up under Irix.  (Thanks to
+   Dan Sullivan.)
+ - Fixed a typo in GC_double_descr in typd_mlc.c.
+   This probably could result in objects described by array descriptors not
+   getting traced correctly.  (Thanks to Ben Hutchings for pointing this out.)
+ - The block nearly full tests in reclaim.c were not correct for 64 bit
+   environments.  This could result in unnecessary heap growth under unlikely
+   conditions.
+
+Since 5.1
+ - dyn_load.c declared GC_scratch_last_end_ptr as an extern even if it
+   was defined as a macro.  This prevented the collector from building on
+   Irix.
+ - We quietly assumed that indirect mark descriptors were never 0.
+   Our own typed allocation interface violated that.  This could result
+   in segmentation faults in the marker with typed allocation.
+ - Fixed a _DUSE_MUNMAP bug in the heap block allocation code.
+   (Thanks to Ben Hutchings for the patch.)
+ - Taught the collector about VC++ handling array operator new.
+   (Thanks again to Ben Hutchings for the patch.)
+ - The two copies of gc_hdrs.h had diverged.  Made one a link to the other
+   again.
+
+Since 5.2  (A few 5.2 patches are not in 6.0alpha1)
+ - Fixed _end declaration for OSF1.
+ - There were lots of spurious leak reports in leak detection mode, caused
+   by the fact that some pages were not being swept, and hence unmarked
+   objects weren't making it onto free lists.  (This bug dated back to 5.0.)
+ - Fixed a typo in the liblinuxgc.so Makefile rule.
+ - Added the GetExitCodeThread to Win32 GC_stop_world to (mostly) work
+   around a Windows 95 GetOpenFileName problem.  (Thanks to Jacob Navia.)
+
+Since 5.3
+ - Fixed a typo that prevented compilation with -DUSE_3DNOW_PREFETCH.
+   (Thanks to Shawn Wagner for actually testing this.)
+ - Fixed GC_is_thread_stack in solaris_threads.c.  It forgot to return a value
+   in the common case.  I wonder why nobody noticed?
+ - Fixed another silly syntax problem in GC_double_descr.  (Thanks to
+   Fergus Henderson for finding it.)
+ - Fixed a GC_gcj_malloc bug: It tended to release the allocator lock twice.
+
+Since 5.4  (A few 5.3 patches are not in 6.0alpha2)
+ - Added HP/PA prefetch support.
+ - Added -DDBG_HDRS_ALL and -DSHORT_DBG_HDRS to reduce the cost and improve
+   the reliability of generating pointer backtrace information, e.g. in
+   the Bigloo environment.
+ - Added parallel marking support (-DPARALLEL_MARK).  This currently
+   works only under IA32 and IA64 Linux, but it shouldn't be hard to adapt
+   to other platforms.  This is intended to be a lighter-weight (less
+   new code, probably not as scalable) solution than the work by Toshio Endo
+   et al, at the University of Tokyo.  A number of their ideas were
+   reused, though the code wasn't, and the underlying data structure
+   is significantly different.  In particular, we keep the global mark
+   stack as a single shared data structure, but most of the work is done
+   on smaller thread-local mark stacks.
+ - Changed GC_malloc_many to be cheaper, and to require less mutual exclusion
+   with -DPARALLEL_MARK.
+ - Added full support for thread local allocation under Linux
+   (-DTHREAD_LOCAL_ALLOC).  This is a thin veneer on GC_malloc_many, and
+   should be easily portable to other platforms, especially those that
+   support pthreads.
+ - CLEAR_DOUBLE was not always getting invoked when it should have been.
+ - GC_gcj_malloc and friends used different out of memory handling than
+   everything else, probably because I forgot about one when I implemented
+   the other.  They now both call GC_oom_fn(), not GC_oom_action().
+ - Integrated Jakub Jelinek's fixes for Linux/SPARC.
+ - Moved GC_objfreelist, GC_aobjfreelist, and GC_words_allocd out of
+   GC_arrays, and separately registered the first two as excluded roots.
+   This makes code compiled with gc_inl.h less dependent on the
+   collector version.  (It would be nice to remove the inclusion of
+   gc_priv.h by gc_inl.h completely, but we're not there yet.  The
+   locking definitions in gc_priv.h are still referenced.)
+   This change was later coniditoned on SEPARATE_GLOBALS, which
+   is not defined by default, since it involves a performance hit.
+ - Register GC_obj_kinds separately as an excluded root region.  The
+   attempt to register it with GC_arrays was usually failing.  (This wasn't
+   serious, but seemed to generate some confusion.) 
+ - Moved backptr.h to gc_backptr.h.
+
+Since 6.0alpha1
+ - Added USE_MARK_BYTES to reduce the need for compare-and-swap on platforms
+   for which that's expensive.
+ - Fixed a locking bug ib GC_gcj_malloc and some locking assertion problems.
+ - Added a missing volatile to OR_WORD and renamed the parameter to
+   GC_compare_and_swap so it's not a C++ reserved word.  (Thanks to
+   Toshio Endo for pointing out both of those.)
+ - Changed Linux dynamic library registration code to look at /proc/self/maps
+   instead of the rld data structures when REDIRECT_MALLOC is defined.
+   Otherwise some of the rld data data structures may be prematurely garbage
+   collected.  (Thanks to Eric Benson for helping to track this down.)
+ - Fixed USE_LD_WRAP a bit more, so it should now work without threads.
+ - Renamed XXX_THREADS macros to GC_XXX_THREADS for namespace correctness.
+   Tomporarily added some backward compatibility definitions.  Renamed
+   USE_LD_WRAP to GC_USE_LD_WRAP.
+ - Many MACOSX POWERPC changes, some additions to the gctest output, and
+   a few minor generic bug fixes.  (Thanks to Dietmar Planitzer.)
+
+Since 6.0 alpha2
+ - Fixed the /proc/self/maps code to not seek, since that apparently is not
+   reliable across all interesting kernels.
+ - Fixed some compilation problems in the absence of PARALLEL_MARK
+   (introduced in alpha2).
+ - Fixed an algorithmic problem with PARALLEL_MARK.  If work needs to
+   be given back to the main mark "stack", the BOTTOM entries of the local
+   stack should be given away, not the top ones.  This has substantial
+   performance impact, especially for > 2 processors, from what I can tell.
+ - Extracted gc_lock.h from gc_priv.h.  This should eventually make it a
+   bit easier to avoid including gc_priv.h in clients.
+ - Moved all include files to include/ and removed duplicate links to the
+   same file.  The old scheme was a bad idea because it was too easy to get the
+   copies out of sync, and many systems don't support hard links.
+   Unfortunately, it's likely that I broke some of the non-Unix Makefiles in
+   the process, although I tried to update them appropriately.
+ - Removed the partial support for a copied nursery.  It's not clear that
+   this would be a tremendous win, since we don't consistently lose to
+   generational copying collectors.  And it would significantly complicate
+   many things.  May be reintroduced if/when it really turns out to win.
+ - Removed references to IRIX_JDK_THREADS, since I believe there never
+   were and never will be any clients.
+ - Added some code to linux_threads.c to possibly support HPUX threads
+   using the Linux code.  Unfortunately, it doesn't work yet, and is
+   currently disabled.
+ - Added support under Linux/X86 for saving the call chain, both in (debug)
+   objects for client debugging, and in GC_arrays._last_stack for GC
+   debugging.  This was previously supported only under Solaris.  It is
+   not enabled by default under X86, since it requires that code be compiled
+   to explicitly dave frame pointers on the call stack.  (With gcc this
+   currently happens by default, but is often turned off explicitly.)
+   To turn it on, define SAVE_CALL_CHAIN.
+ 
+Since 6.0 alpha3
+ - Moved up the detection of mostly full blocks to the initiatiation of the
+   sweep phase.  This eliminates some lock conention in the PARALLEL_MARK case,
+   as multiple threads try to look at mostly full blocks concurrently.
+ - Restored the code in GC_malloc_many that grabs a prefix of the global
+   free list.  This avoids the case in which every GC_malloc_many call
+   tries and fails to allocate a new heap block, and the returns a single
+   object from the global free list.
+ - Some minor fixes in new_hblk.c.  (Attempted to build free lists in order
+   of increasing addresses instead of decreasing addresses for cache performance
+   reasons.  But this seems to be only a very minor gain with -DEAGER_SWEEP,
+   and a loss in other cases.  So the change was backed out.)
+ - Fixed some of the documentation.  (Thanks in large part to Fergus
+   Henderson.)
+ - Fixed the Linux USE_PROC_FOR_LIBRARIES code to deal with apps that perform
+   large numbers of mmaps.  (Thanks to Eric Benson.)  Also fixed that code to
+   deal with short reads.
+ - Added GC_get_total_bytes(). 
+ - Fixed leak detection mode to avoid spurious messages under linuxthreads.
+   (This should also now be easy for the other supported threads packages.
+   But the code is tricky enough that I'm hesitant to do it without being able
+   to test.  Everything allocated in the GC thread support itself should be
+   explicitly deallocated.)
+ - Made it possible (with luck) to redirect malloc to GC_local_malloc.
+
+Since 6.0 alpha4
+ - Changed the definition of GC_pause in linux_threads.c to use a volatile
+   asm.  Some versions of gcc apparently optimize away writes to local volatile
+   variables.  This caused poor locking behaviour starting at about
+   4 processors.
+ - Added GC_start_blocking(), GC_end_blocking() calls and wrapper for sleep
+   to linux_threads.c.
+   The first two calls could be used to generally avoid sending GC signals to
+   blocked threads, avoiding both premature wakeups and unnecessary overhead.
+ - Fixed a serious bug in thread-local allocation.  At thread termination,
+   GC_free could get called on small integers.  Changed the code for thread
+   termination to more efficiently return left-over free-lists.
+ - Integrated Kjetil Matheussen's BeOS support.
+ - Rearranged the directory structure to create the doc and tests
+   subdirectories.
+ - Sort of integrated Eric Benson's patch for OSF1.  This provided basic
+   OSF1 thread support by suitably extending hpux_irix_threads.c.  Based
+   on earlier email conversations with David Butenhof, I suspect that it
+   will be more reliable in the long run to base this on linux_threads.c
+   instead.  Thus I attempted to patch up linux_threads.c based on Eric's code.
+   The result is almost certainly broken, but hopefully close enough that
+   someone with access to a machine can pick it up.
+ - Integrated lots of minor changes from the NetBSD distribution.  (These
+   were supplied by David Brownlee.  I'm not sure about the original
+   authors.)
+ - Hacked a bit more on the HP/UX thread-support in linux_threads.c.  It
+   now appears to work in the absence of incremental collection.  Renamed
+   hpux_irix_threads.c back to irix_threads.c, and removed the attempt to
+   support HPUX there.
+ - Changed gc.h to define _REENTRANT in cases in which it should already
+   have been defined. It is still safer to also define it on the command
+   line. 
+
+Since 6.0alpha5:
+ - Changed the definition of DATASTART on ALPHA and IA64, where data_start
+   and __data_start are not defined by earlier versions of glibc.  This might
+   need to be fixed on other platforms as well.
+ - Changed the way the stack base and backing store base are found on IA64.
+   This should now remain reliable on future kernels.  But since it relies
+   on /proc, it will no longer work in the simulated NUE environment.
+ - Made the call to random() in dbg_mlc.c with -DKEEP_BACK_PTRS dependent
+   on the OS.  On non-Unix systems, rand() should be used instead.  Handled
+   small RAND_MAX.  (Thanks to Peter Ross for pointing this out.)
+ - Fixed the cord make rules to create the cord subdirectory, if necessary.
+   (Thanks to Doug Moen.)
+ - Changed fo_object_size calculation in finalize.c.  Turned finalization
+   of nonheap object into a no-op.  Removed anachronism from GC_size()
+   implementation.
+ - Changed GC_push_dirty call in solaris_threads.c to GC_push_selected.
+   It was missed in a previous renaming. (Thanks to Vladimir Tsichevski
+   for pointing this out.)
+ - Arranged to not not mask SIGABRT in linux_threads.c.  (Thanks to Bryce
+   McKinlay.) 
+ - Added GC_no_dls hook for applications that want to register their own
+   roots.
+ - Integrated Kjetil Matheussen's Amiga changes.
+ - Added FREEBSD_STACKBOTTOM.  Changed the X86/FreeBSD port to use it.
+   (Thanks to Matthew Flatt.)
+ - Added pthread_detach interception for platforms supported by linux_threads.c
+   and irix_threads.c.  Should also be added for Solaris?
+ - Changed the USE_MMAP code to check for the case in which we got the
+   high end of the address space, i.e. mem_ptr + mem_sz == 0.  It appears
+   that this can happen under Solaris 7.  It seems to be allowed by what
+   I would claim is an oversight in the mmap specification.  (Thanks to Toshio
+   Endo for pointing out the problem.)
+ - Cleanup of linux_threads.c.  Some code was originally cloned from
+   irix_threads.c and now unnecessary.  Some comments were obviously wrong.
+ - (Mostly) fixed a longstanding problem with setting of dirty bits from
+   a signal handler.  In the presence of threads, dirty bits could get lost,
+   since the etting of a bit in the bit vector was not atomic with respect
+   to other updates.  The fix is 100% correct only for platforms for which
+   GC_test_and_set is defined.  The goal is to make that all platforms with
+   thread support.  Matters only if incremental GC and threads are both
+   enabled.
+ - made GC_all_interior_pointers (a.k.a. ALL_INTERIOR_POINTERS) an
+   initialization time, instead of build-time option.  This is a 
+   nontrivial, high risk change.  It should slow down the code measurably
+   only if MERGE_SIZES is not defined, which is a very nonstandard
+   configuration.   
+ - Added doc/README.environment, and implemented what it describes.  This
+   allows a number of additional configuration options to be set through
+   the environment.  It documents a few previously undocumented options.
+ - Integrated Eric Benson's leak testing improvements.
+ - Removed the option to throw away the beginning of each page (DISCARD_WORDS).
+   This became less and less useful as processors enforce stricter alignment.
+   And it hadn't been tested in ages, and was thus probably broken anyway.
+
+Since 6.0alpha6:
+ - Added GC_finalizer_notifier.  Fixed GC_finalize_on_demand.  (The variable
+   actually wasn't being tested at the right points.  The build-time flag
+   was.)
+ - Added Tom Tromey's S390 Linux patch.
+ - Added code to push GC_finalize_now in GC_push_finalizer_structures.
+   (Thanks to Matthew Flatt.)
+ - Added GC_push_gc_structures() to push all GC internal roots.
+ - Integrated some FreeBSD changes from Matthew Flatt.
+ - It looks like USRSTACK is not always correctly defined under Solaris.
+   Hacked gcconfig.h to attempt to work around the problem.  The result
+   is not well tested.  (Thanks again to Matthew Flatt for pointing this
+   out.  The gross hack is mine. - HB)
+ - Added Ji-Yong Chung's win32 threads and C++ fixes.
+ - Arranged for hpux_test_and_clear.s to no longer be needed or built.
+   It was causing build problems with gas, and it's not clear this is
+   better than the pthreads alternative on this platform.
+ - Some MINGW32 fixes from Hubert Garavel.
+ - Added Initial Hitachi SH4 port from Kaz Kojima.
+ - Ported thread-local allocation and parallel mark code to HP/UX on PA_RISC.
+ - Made include/gc_mark.h more public and separated out the really private
+   pieces.  This is probably still not quite sufficient for clients that
+   want to supply their own kind of type information.  But it's a start.
+   This involved lots of identifier renaming to make it namespace clean.
+ - Added GC_dont_precollect for clients that need complete control over
+   the root set.
+ - GC_is_visible didn't do the right thing with gcj objects.  (Not that
+   many people are likely to care, but ...)
+ - Don't redefine read with GC_USE_LD_WRAP.
+ - Initial port to LINUX/HP_PA.  Incremental collection and threads are not
+   yet supported.  (Incremental collection should work if you have the
+   right kernel.  Threads may work with a sufficiently patched pthread
+   library.)
+ - Changed gcconfig.h to recognize __i386__ as an alternative to i386 in
+   many places.  (Thanks to Benjamin Lerman.)
+ - Made win32_threads.c more tolerant of detaching a thread that it didn't
+   know about.  (Thanks to Paul Nash.)
+ - Added Makefile.am and configure.in from gcc to the distribution, with
+   minimal changes.  For the moment, those are just placeholders.  In the
+   future, we're planning to switch to a GNU-style build environment for
+   Un*x-like systems, though the old Makefile will remain as a backup.
+ - Turned off STUBBORN_ALLOC by default, and added it back as a Makefile
+   option.
+ - Redistributed some functions between malloc.c and mallocx.c, so that
+   simple statically linked apps no longer pull in mallocx.o.
+ - Changed large object allocation to clear the first and last few words
+   of each block before releassing the lock.  Otherwise the marker could see
+   objects with nonsensical type descriptors.
+ - Fixed a couple of subtle problems that could result in not recognizing
+   interior pointers from the stack.  (I believe these were introduced
+   in 6.0alpha6.)
+ - GC_debug_free_inner called GC_free, which tried to reacquire the
+   allocator lock, and hence deadlocked.  (DBG_HDRS_ALL probably never worked
+   with threads?)
+ - Fixed several problems with back traces.  Accidental references to a free
+   list could cause the free list pointer to be overwritten by a back pointer.
+   There seemed to be some problems with the encoding of root and finalizer
+   references.
+  
+Since 6.0alpha7:
+ - Changed GC_debug_malloc_replacement and GC_debug_realloc_replacement
+   so that they compile under Irix.  (Thanks to Dave Love.)
+ - Updated powerpc_macosx_mach_dep.s so that it works if the collector
+   is in a dynamic library.  (Thanks to Andrew Begel.)
+ - Transformed README.debugging into debugging.html, updating and
+   expanding it in the process.  Added gcdescr.html and tree.html
+   from the web site to the GC distribution.
+ - Fixed several problems related to PRINT_BLACK_LIST. This involved
+   restructuring some of the marker macros.
+ - Fixed some problems with the sizing of objects with debug information.
+   Finalization was broken KEEP_BACK_PTRS or PRINT_BLACK_LIST.  Reduced the
+   object size with SHORT_DEBUG_HDRS by another word.
+ - The "Needed to allocate blacklisted ..." warning had inadvertently
+   been turned off by default, due to a buggy test in allchblk.c.  Turned
+   it back on.
+ - Removed the marker macros to deal with 2 pointers in interleaved fashion.
+   They were messy and the performance improvement seemed minimal.  We'll
+   leave such scheduling issues to the compiler.
+ - Changed Linux/PowerPC test to also check for __powerpc__ in response
+   to a discussion on the gcc mailing list.
+ - On Matthew Flatt's suggestion removed the "static" from the jmp_buf
+   declaration in GC_generic_push_regs.  This was causing problems in
+   systems that register all of their own roots.  It looks far more correct
+   to me without the "static" anyway. 
+ - Fixed several problems with thread local allocation of pointerfree or
+   typed objects.  The collector was reclaiming thread-local free lists, since
+   it wasn't following the link fields.
+ - There was apparently a long-standing race condition related to multithreaded
+   incremental collection.  A collection could be started and a thread stopped
+   between the memory unprotect system call and the setting of the
+   corresponding dirt bit.  I believe this did not affect Solaris or PCR, which
+   use a different dirty-bit implementation.  Fixed this by installing
+   signal handlers with sigaction instead of signal, and disabling the thread
+   suspend signal while in the write-protect handler.  (It is unclear
+   whether this scenario ever actually occurred.  I found it while tracking
+   down the following:)
+ - Incremental collection did not cooperate correctly with the PARALLEL_MARK
+   implementation of GC_malloc_many or the local_malloc primitves.  It still
+   doesn't work well, but it shouldn't lose memory anymore.
+ - Integrated some changes from the gcc source tree that I had previously
+   missed.  (Thanks to Bryce McKinley for the reminder/diff.)
+ - Added Makefile.direct as a copy of the default Makefile, which would
+   normally be overwritten if configure is run.
+ - Changed the gc.tar target in Makefile.direct to embed the version number
+   in the gc directory name.  This will affect future tar file distributions.
+ - Changed the Irix dynamic library finding code to no longer try to
+   eliminate writable text segments under Irix6.x, since that is probably no
+   longer necessary, and can apparently be unsafe on occasion.  (Thanks to
+   Shiro Kawai for pointing this out.)
+ - GC_cleanup with GC_DEBUG enabled passed a real object base address to
+   GC_debug_register_finalizer_ignore_self, which expected a pointer past the
+   debug header.  Call GC_register_finalizer_ignore_self instead, even with
+   debugging enabled.  (Thanks to Jean-Daniel Fekete for catching this.)
+ - The collector didn't build with call chain saving enabled but NARGS=0.
+   (Thanks to Maarten Thibaut.)
+ - Fixed up the GNU-style build files enough so that they work in some
+   obvious cases.
+ - Added initial port to Digital Mars compiler for win32. (Thanks to Walter
+   Bright.)
+
+Since 6.0alpha8:
+ - added README.macros.
+ - Made gc.mak a symbolic link to work around winzip's tendency to ignore
+   hard links.
+ - Simplified the setting of NEED_FIND_LIMIT in os_dep.c, possibly breaking
+   it on untested platforms.
+ - Integrated initial GNU HURD port. (Thanks to Chris Lingard and Igor
+   Khavkine.)
+ - A few more fixes for Digital Mars compiler.
+ - Fixed gcc version recognition.  Renamed OPERATOR_NEW_ARRAY to
+   GC_OPERATOR_NEW_ARRAY.  Changed GC_OPERATOR_NEW_ARRAY to be the default.
+   It can be overridden with -DGC_NO_OPERATOR_NEW_ARRAY.  (Thanks to
+   Cesar Eduardo Barros.) 
+ - Changed the byte size to free-list mapping in thread local allocation
+   so that size 0 allocations are handled correctly.
+ - Fixed Linux/MIPS stackbottom for new toolchain. (Thanks to Ryan Murray.)
+ - Changed finalization registration to invoke GC_oom_fn when it runs out
+   of memory.
+ - Removed lvalue cast in finalize.c.  This caused some debug configurations
+   not to build with some non-gcc compilers.
+
+Since 6.0alpha9:
+ - Two more bug fixes for KEEP_BACK_PTRS and DBG_HDRS_ALL.
+ - Fixed a stack clearing problem that resulted in SIGILL with a
+   misaligned stack pointer for multithreaded SPARC builds.
+ - Integrated another HURD patch (thanks to Igor Khavkine).
+ 
+
+To do:
+ - There seem to be outstanding issues on Solaris/X86, possibly with
+   finding the data segment starting address.  Information/patches would
+   ne appreciated.
+ - New_gc_alloc.h is apparently no longer compatible with the latest C++
+   standard library in gcc3.0.  (This isn't technically a bug, since it only
+   claimed compatibility with the SGI STL.  But we may need a new C++ STL
+   allocator interface.)
+ - Very large root set sizes (> 16 MB or so) could cause the collector
+   to abort with an unexpected mark stack overflow.  (Thanks again to
+   Peter Chubb.)  NOT YET FIXED.  Workaround is to increase the initial
+   size.
+ - The SGI version of the collector marks from mmapped pages, even
+   if they are not part of dynamic library static data areas.  This
+   causes performance problems with some SGI libraries that use mmap
+   as a bitmap allocator.  NOT YET FIXED.  It may be possible to turn
+   off DYNAMIC_LOADING in the collector as a workaround.  It may also
+   be possible to conditionally intercept mmap and use GC_exclude_static_roots.
+   The real fix is to walk rld data structures, which looks possible.
+ - Incremental collector should handle large objects better.  Currently,
+   it looks like the whole object is treated as dirty if any part of it
+   is.
+ - Cord/cordprnt.c doesn't build on a few platforms (notably PowerPC), since
+   we make some unwarranted assumptions about how varargs are handled.  This
+   currently makes the cord-aware versions of printf unusable on some platforms.
+   Fixing this is unfortunately not trivial.
diff --git a/gc/doc/README.contributors b/gc/doc/README.contributors
new file mode 100644
index 0000000..fd5c95f
--- /dev/null
+++ b/gc/doc/README.contributors
@@ -0,0 +1,57 @@
+This is an attempt to acknowledge early contributions to the garbage
+collector.  Later contributions should instead be mentioned in
+README.changes.
+
+HISTORY -
+
+  Early versions of this collector were developed as a part of research
+projects supported in part by the National Science Foundation
+and the Defense Advance Research Projects Agency.
+
+The garbage collector originated as part of the run-time system for
+the Russell programming language implementation. The first version of the
+garbage collector was written primarily by Al Demers.  It was then refined
+and mostly rewritten, primarily by Hans-J. Boehm, at Cornell U., 
+the University of Washington, Rice University (where it was first used for
+C and assembly code), Xerox PARC, SGI, and HP Labs.  However, significant
+contributions have also been made by many others.
+
+Some other contributors:  
+
+More recent contributors are mentioned in the modification history in
+README.changes.  My apologies for any omissions.
+
+The SPARC specific code was originally contributed by Mark Weiser.
+The Encore Multimax modifications were supplied by
+Kevin Kenny (kenny@m.cs.uiuc.edu).  The adaptation to the IBM PC/RT is largely
+due to Vernon Lee, on machines made available to Rice by IBM.
+Much of the HP specific code and a number of good suggestions for improving the
+generic code are due to Walter Underwood.
+Robert Brazile (brazile@diamond.bbn.com) originally supplied the ULTRIX code.
+Al Dosser (dosser@src.dec.com) and Regis Cridlig (Regis.Cridlig@cl.cam.ac.uk)
+subsequently provided updates and information on variation between ULTRIX
+systems.  Parag Patel (parag@netcom.com) supplied the A/UX code.
+Jesper Peterson(jep@mtiame.mtia.oz.au), Michel Schinz, and
+Martin Tauchmann (martintauchmann@bigfoot.com) supplied the Amiga port.
+Thomas Funke (thf@zelator.in-berlin.de(?)) and
+Brian D.Carlstrom (bdc@clark.lcs.mit.edu) supplied the NeXT ports.
+Douglas Steel (doug@wg.icl.co.uk) provided ICL DRS6000 code.
+Bill Janssen (janssen@parc.xerox.com) supplied the SunOS dynamic loader
+specific code. Manuel Serrano (serrano@cornas.inria.fr) supplied linux and
+Sony News specific code.  Al Dosser provided Alpha/OSF/1 code.  He and
+Dave Detlefs(detlefs@src.dec.com) also provided several generic bug fixes.
+Alistair G. Crooks(agc@uts.amdahl.com) supplied the NetBSD and 386BSD ports.
+Jeffrey Hsu (hsu@soda.berkeley.edu) provided the FreeBSD port.
+Brent Benson (brent@jade.ssd.csd.harris.com) ported the collector to
+a Motorola 88K processor running CX/UX (Harris NightHawk).
+Ari Huttunen (Ari.Huttunen@hut.fi) generalized the OS/2 port to
+nonIBM development environments (a nontrivial task).
+Patrick Beard (beard@cs.ucdavis.edu) provided the initial MacOS port.
+David Chase, then at Olivetti Research, suggested several improvements.
+Scott Schwartz (schwartz@groucho.cse.psu.edu) supplied some of the
+code to save and print call stacks for leak detection on a SPARC.
+Jesse Hull and John Ellis supplied the C++ interface code.
+Zhong Shao performed much of the experimentation that led to the
+current typed allocation facility.  (His dynamic type inference code hasn't
+made it into the released version of the collector, yet.)
+
diff --git a/gc/doc/README.cords b/gc/doc/README.cords
new file mode 100644
index 0000000..3485e01
--- /dev/null
+++ b/gc/doc/README.cords
@@ -0,0 +1,53 @@
+Copyright (c) 1993-1994 by Xerox Corporation.  All rights reserved.
+
+THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+
+Permission is hereby granted to use or copy this program
+for any purpose,  provided the above notices are retained on all copies.
+Permission to modify the code and to distribute modified code is granted,
+provided the above notices are retained, and a notice that the code was
+modified is included with the above copyright notice.
+
+Please send bug reports to Hans-J. Boehm (Hans_Boehm@hp.com or
+boehm@acm.org).
+
+This is a string packages that uses a tree-based representation.
+See cord.h for a description of the functions provided.  Ec.h describes
+"extensible cords", which are essentially output streams that write
+to a cord.  These allow for efficient construction of cords without
+requiring a bound on the size of a cord.
+
+More details on the data structure can be found in
+
+Boehm, Atkinson, and Plass, "Ropes: An Alternative to Strings",
+Software Practice and Experience 25, 12, December 1995, pp. 1315-1330.
+
+A fundamentally similar "rope" data structure is also part of SGI's standard
+template library implementation, and its descendents, which include the
+GNU C++ library.  That uses reference counting by default.
+There is a short description of that data structure at
+http://reality.sgi.com/boehm/ropeimpl.html .  (The more official location
+http://www.sgi.com/tech/stl/ropeimpl.html is missing a figure.)
+
+All of these are descendents of the "ropes" in Xerox Cedar.
+
+de.c is a very dumb text editor that illustrates the use of cords.
+It maintains a list of file versions.  Each version is simply a
+cord representing the file contents.  Nonetheless, standard
+editing operations are efficient, even on very large files.
+(Its 3 line "user manual" can be obtained by invoking it without
+arguments.  Note that ^R^N and ^R^P move the cursor by
+almost a screen.  It does not understand tabs, which will show
+up as highlighred "I"s.  Use the UNIX "expand" program first.)
+To build the editor, type "make cord/de" in the gc directory.
+
+This package assumes an ANSI C compiler such as gcc.  It will
+not compile with an old-style K&R compiler.
+
+Note that CORD_printf iand friends use C functions with variable numbers
+of arguments in non-standard-conforming ways.  This code is known to
+break on some platforms, notably PowerPC.  It should be possible to
+build the remainder of the library (everything but cordprnt.c) on
+any platform that supports the collector.
+ 
diff --git a/gc/doc/README.dj b/gc/doc/README.dj
new file mode 100644
index 0000000..613bc42
--- /dev/null
+++ b/gc/doc/README.dj
@@ -0,0 +1,12 @@
+[Original version supplied by Xiaokun Zhu <xiaokun@aero.gla.ac.uk>]
+[This version came mostly from Gary Leavens.			  ]
+
+Look first at Makefile.dj, and possibly change the definitions of
+RM and MV if you don't have rm and mv installed.
+Then use Makefile.dj to compile the garbage collector.
+For example, you can do:
+
+	make -f Makefile.dj test
+
+All the tests should work fine.
+
diff --git a/gc/doc/README.environment b/gc/doc/README.environment
new file mode 100644
index 0000000..5760342
--- /dev/null
+++ b/gc/doc/README.environment
@@ -0,0 +1,44 @@
+The garbage collector looks at a number of environment variables which are
+the used to affect its operation.  These are examined only on Un*x-like
+platforms.
+
+GC_INITIAL_HEAP_SIZE=<bytes> -	Initial heap size in bytes.  May speed up
+				process start-up.
+
+GC_LOOP_ON_ABORT - Causes the collector abort routine to enter a tight loop.
+		   This may make it easier to debug, such a process, especially
+		   for multithreaded platforms that don't produce usable core
+		   files, or if a core file would be too large.  On some
+		   platforms, this also causes SIGSEGV to be caught and
+		   result in an infinite loop in a handler, allowing
+		   similar debugging techniques.
+
+GC_PRINT_STATS - Turn on as much logging as is easily feasible without
+		 adding signifcant runtime overhead.  Doesn't work if
+		 the collector is built with SMALL_CONFIG.  Overridden
+		 by setting GC_quiet.  On by default if the collector
+		 was built without -DSILENT.
+
+GC_PRINT_ADDRESS_MAP - Linux only.  Dump /proc/self/maps, i.e. various address
+		       maps for the process, to stderr on every GC.  Useful for
+		       mapping root addresses to source for deciphering leak
+		       reports.
+
+GC_NPROCS=<n> - Linux w/threads only.  Explicitly sets the number of processors
+	        that the GC should expect to use.  Note that setting this to 1
+		when multiple processors are available will preserve
+		correctness, but may lead to really horrible performance.
+
+GC_NO_BLACKLIST_WARNING - Prevents the collector from issuing
+		"Needed to allocate blacklisted block at ..." warnings.
+
+The following turn on runtime flags that are also program settable.  Checked
+only during initialization.  We expect that they will usually be set through
+other means, but this may help with debugging and testing:
+
+GC_FIND_LEAK - Turns on GC_find_leak and thus leak detection.
+
+GC_ALL_INTERIOR_POINTERS - Turns on GC_all_interior_pointers and thus interior
+			   pointer recognition.
+
+GC_DONT_GC - Turns off garbage collection.  Use cautiously.
diff --git a/gc/doc/README.hp b/gc/doc/README.hp
new file mode 100644
index 0000000..caa8bdd
--- /dev/null
+++ b/gc/doc/README.hp
@@ -0,0 +1,18 @@
+Dynamic loading support requires that executables be linked with -ldld.
+The alternative is to build the collector without defining DYNAMIC_LOADING
+in gcconfig.h and ensuring that all garbage collectable objects are
+accessible without considering statically allocated variables in dynamic
+libraries.
+
+The collector should compile with either plain cc or cc -Ae.  Cc -Aa
+fails to define _HPUX_SOURCE and thus will not configure the collector
+correctly.
+
+Incremental collection support was reccently added, and should now work.
+
+In spite of past claims, pthread support under HP/UX 11 should now work.
+Define GC_HPUX_THREADS for the build.  Incremental collection still does not
+work in combination with it.
+
+The stack finding code can be confused by putenv calls before collector
+initialization.  Call GC_malloc or GC_init before any putenv calls.
diff --git a/gc/doc/README.linux b/gc/doc/README.linux
new file mode 100644
index 0000000..efd0a26
--- /dev/null
+++ b/gc/doc/README.linux
@@ -0,0 +1,135 @@
+See README.alpha for Linux on DEC AXP info.
+
+This file applies mostly to Linux/Intel IA32.  Ports to Linux on an M68K
+and PowerPC are also integrated.  They should behave similarly, except that
+the PowerPC port lacks incremental GC support, and it is unknown to what
+extent the Linux threads code is functional.  See below for M68K specific
+notes.
+
+Incremental GC is supported on Intel IA32 and M68K.
+
+Dynamic libraries are supported on an ELF system.  A static executable
+should be linked with the gcc option "-Wl,-defsym,_DYNAMIC=0".
+
+The collector appears to work with Linux threads.  We have seen
+intermittent hangs in sem_wait.  So far we have been unable to reproduce
+these unless the process was being debugged or traced.  Thus it's
+possible that the only real issue is that the debugger loses
+signals on rare occasions.
+
+The garbage collector uses SIGPWR and SIGXCPU if it is used with
+Linux threads.  These should not be touched by the client program.
+
+To use threads, you need to abide by the following requirements:
+
+1) You need to use LinuxThreads (which are included in libc6).
+
+   The collector relies on some implementation details of the LinuxThreads
+   package.  It is unlikely that this code will work on other
+   pthread implementations (in particular it will *not* work with
+   MIT pthreads).
+
+2) You must compile the collector with -DGC_LINUX_THREADS and -D_REENTRANT
+   specified in the Makefile.
+
+3a) Every file that makes thread calls should define GC_LINUX_THREADS and 
+   _REENTRANT and then include gc.h.  Gc.h redefines some of the
+   pthread primitives as macros which also provide the collector with
+   information it requires.
+
+3b) A new alternative to (3a) is to build the collector and compile GC clients
+   with -DGC_USE_LD_WRAP, and to link the final program with
+
+   (for ld) --wrap read --wrap dlopen --wrap pthread_create \
+	    --wrap pthread_join --wrap pthread_detach \
+	    --wrap pthread_sigmask --wrap sleep
+
+   (for gcc) -Wl,--wrap -Wl,read -Wl,--wrap -Wl,dlopen -Wl,--wrap \
+	     -Wl,pthread_create -Wl,--wrap -Wl,pthread_join -Wl,--wrap \
+	     -Wl,pthread_detach -Wl,--wrap -Wl,pthread_sigmask \
+	     -Wl,--wrap -Wl,sleep
+
+   In any case, _REENTRANT should be defined during compilation.
+
+4) Dlopen() disables collection during its execution.  (It can't run
+   concurrently with the collector, since the collector looks at its
+   data structures.  It can't acquire the allocator lock, since arbitrary
+   user startup code may run as part of dlopen().)  Under unusual
+   conditions, this may cause unexpected heap growth.
+
+5) The combination of GC_LINUX_THREADS, REDIRECT_MALLOC, and incremental
+   collection fails in seemingly random places.  This hasn't been tracked
+   down yet, but is perhaps not completely astonishing.  The thread package
+   uses malloc, and thus can presumably get SIGSEGVs while inside the
+   package.  There is no real guarantee that signals are handled properly
+   at that point.
+
+6) Thread local storage may not be viewed as part of the root set by the
+   collector.  This probably depends on the linuxthreads version.  For the
+   time being, any collectable memory referenced by thread local storage should
+   also be referenced from elsewhere, or be allocated as uncollectable.
+   (This is really a bug that should be fixed somehow.)
+
+
+M68K LINUX:
+(From Richard Zidlicky)
+The bad news is that it can crash every linux-m68k kernel on a 68040,
+so an additional test is needed somewhere on startup. I have meanwhile
+patches to correct the problem in 68040 buserror handler but it is not
+yet in any standard kernel.
+
+Here is a simple test program to detect whether the kernel has the
+problem. It could be run as a separate check in configure or tested 
+upon startup. If it fails (return !0) than mprotect can't be used
+on that system.
+
+/*
+ * test for bug that may crash 68040 based Linux
+ */
+
+#include <sys/mman.h>
+#include <signal.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+char *membase;
+int pagesize=4096;
+int pageshift=12;
+int x_taken=0;
+
+int sighandler(int sig)
+{
+   mprotect(membase,pagesize,PROT_READ|PROT_WRITE);
+   x_taken=1;
+}
+
+main()
+{
+  long l;
+
+   signal(SIGSEGV,sighandler);
+   l=(long)mmap(NULL,pagesize,PROT_READ,MAP_PRIVATE | MAP_ANON,-1,0);
+  if (l==-1)
+     {
+       perror("mmap/malloc");
+       abort();
+     }
+  membase=(char*)l;
+    *(long*)(membase+sizeof(long))=123456789;
+  if (*(long*)(membase+sizeof(long)) != 123456789 )
+    {
+      fprintf(stderr,"writeback failed !\n");
+      exit(1);
+    }
+  if (!x_taken)
+    {
+      fprintf(stderr,"exception not taken !\n");
+      exit(1);
+    }
+  fprintf(stderr,"vmtest Ok\n");
+  exit(0);
+}
+
+
diff --git a/gc/doc/README.macros b/gc/doc/README.macros
new file mode 100644
index 0000000..d9df8dd
--- /dev/null
+++ b/gc/doc/README.macros
@@ -0,0 +1,78 @@
+The collector uses a large amount of conditional compilation in order to
+deal with platform dependencies.  This violates a number of known coding
+standards.  On the other hand, it seems to be the only practical way to
+support this many platforms without excessive code duplication. 
+
+A few guidelines have mostly been followed in order to keep this manageable:
+
+1) #if and #ifdef directives are properly indented whenever easily possible.
+All known C compilers allow whitespace between the "#" and the "if" to make
+this possible.  ANSI C also allows white space before the "#", though we
+avoid that.  It has the known disadvantages that it differs from the normal
+GNU conventions, and that it makes patches larger than otherwise necessary.
+In my opinion, it's still well worth it, for the same reason that we indent
+ordinary "if" statements.
+
+2) Whenever possible, tests are performed on the macros defined in gcconfig.h
+instead of directly testing patform-specific predefined macros.  This makes it
+relatively easy to adapt to new compilers with a different set of predefined
+macros.  Currently these macros generally identify platforms instead of
+features.  In many cases, this is a mistake.
+
+3) The code currently avoids #elif, eventhough that would make it more
+readable.  This was done since #elif would need to be understood by ALL
+compilers used to build the collector, and that hasn't always been the case.
+It makes sense to reconsider this decision at some point, since #elif has been
+standardized at least since 1989.
+
+Many of the tested configuration macros are at least somewhat defined in
+either include/private/gcconfig.h or in Makefile.direct.  Here is an attempt
+at defining some of the remainder:  (Thanks to Walter Bright for suggesting
+this.  This is a work in progress)
+
+MACRO		EXPLANATION
+-----		-----------
+
+__DMC__	Always #define'd by the Digital Mars compiler. Expands
+		to the compiler version number in hex, i.e. 0x810 is
+		version 8.1b0
+
+_ENABLE_ARRAYNEW
+		#define'd by the Digital Mars C++ compiler when
+		operator new[] and delete[] are separately
+		overloadable. Used in gc_cpp.h.
+
+_MSC_VER	Expands to the Visual C++ compiler version.  Assumed to
+		not be defined for other compilers (at least if they behave
+		appreciably differently).
+
+_DLL		Defined by Visual C++ if dynamic libraries are being built
+		or used.  Used to test whether __declspec(dllimport) or
+		__declspec(dllexport) needs to be added to declarations
+		to support the case in which the collector is in a dll.
+
+GC_DLL		User-settable macro that forces the effect of _DLL.
+
+GC_NOT_DLL	User-settable macro that overrides _DLL, e.g. if dynamic
+		libraries are used, but the collector is in a static library.
+
+__STDC__	Assumed to be defined only by compilers that understand
+		prototypes and other C89 features.  Its value is generally
+		not used, since we are fine with most nonconforming extensions.
+
+SUNOS5SIGS	Solaris-like signal handling.  This is probably misnamed,
+		since it really doesn't guarantee much more than Posix.
+		Currently set only for Solaris2.X, HPUX, and DRSNX.  Should
+		probably be set for some other platforms.
+
+PCR		Set if the collector is being built as part of the Xerox
+		Portable Common Runtime.
+
+SRC_M3		Set if the collector is being built as a replacement of the
+		one in the DEC/Compaq SRC Modula-3 runtime.  I suspect this
+		was last used around 1994, and no doubt broke a long time ago.
+		It's there primarily incase someone wants to port to a similar
+		system.
+
+
+
diff --git a/gc/doc/README.rs6000 b/gc/doc/README.rs6000
new file mode 100644
index 0000000..f5630b2
--- /dev/null
+++ b/gc/doc/README.rs6000
@@ -0,0 +1,9 @@
+We have so far failed to find a good way to determine the stack base.
+It is highly recommended that GC_stackbottom be set explicitly on program
+startup.  The supplied value sometimes causes failure under AIX 4.1, though
+it appears to work under 3.X.  HEURISTIC2 seems to work under 4.1, but
+involves a substantial performance penalty, and will fail if there is
+no limit on stack size.
+
+There is no thread support.  (I assume recent versions of AIX provide
+pthreads?  I no longer have access to a machine ...)
diff --git a/gc/doc/README.sgi b/gc/doc/README.sgi
new file mode 100644
index 0000000..7bdb50a
--- /dev/null
+++ b/gc/doc/README.sgi
@@ -0,0 +1,41 @@
+Performance of the incremental collector can be greatly enhanced with
+-DNO_EXECUTE_PERMISSION.
+
+The collector should run with all of the -32, -n32 and -64 ABIs.  Remember to
+define the AS macro in the Makefile to be "as -64", or "as -n32".
+
+If you use -DREDIRECT_MALLOC=GC_malloc with C++ code, your code should make
+at least one explicit call to malloc instead of new to ensure that the proper
+version of malloc is linked in.
+
+Sproc threads are not supported in this version, though there may exist other
+ports.
+
+Pthreads support is provided.  This requires that:
+
+1) You compile the collector with -DGC_IRIX_THREADS specified in the Makefile.
+
+2) You have the latest pthreads patches installed.  
+
+(Though the collector makes only documented pthread calls,
+it relies on signal/threads interactions working just right in ways
+that are not required by the standard.  It is unlikely that this code
+will run on other pthreads platforms.  But please tell me if it does.)
+
+3) Every file that makes thread calls should define IRIX_THREADS and then
+include gc.h.  Gc.h redefines some of the pthread primitives as macros which
+also provide the collector with information it requires.
+
+4) pthread_cond_wait and pthread_cond_timed_wait should be prepared for
+premature wakeups.  (I believe the pthreads and realted standards require this
+anyway.  Irix pthreads often terminate a wait if a signal arrives.
+The garbage collector uses signals to stop threads.)
+
+5) It is expensive to stop a thread waiting in IO at the time the request is
+initiated.  Applications with many such threads may not exhibit acceptable
+performance with the collector.  (Increasing the heap size may help.)
+
+6) The collector should not be compiled with -DREDIRECT_MALLOC.  This
+confuses some library calls made by the pthreads implementation, which
+expect the standard malloc.
+
diff --git a/gc/doc/README.solaris2 b/gc/doc/README.solaris2
new file mode 100644
index 0000000..6ed61dc
--- /dev/null
+++ b/gc/doc/README.solaris2
@@ -0,0 +1,62 @@
+The collector supports both incremental collection and threads under
+Solaris 2.  The incremental collector normally retrieves page dirty information
+through the appropriate /proc calls.  But it can also be configured
+(by defining MPROTECT_VDB instead of PROC_VDB in gcconfig.h) to use mprotect
+and signals.  This may result in shorter pause times, but it is no longer
+safe to issue arbitrary system calls that write to the heap.
+
+Under other UNIX versions,
+the collector normally obtains memory through sbrk.  There is some reason
+to expect that this is not safe if the client program also calls the system
+malloc, or especially realloc.  The sbrk man page strongly suggests this is
+not safe: "Many library routines use malloc() internally, so use brk()
+and sbrk() only when you know  that malloc() definitely will not be used by
+any library routine."  This doesn't make a lot of sense to me, since there
+seems to be no documentation as to which routines can transitively call malloc.
+Nonetheless, under Solaris2, the collector now (since 4.12) allocates
+memory using mmap by default.  (It defines USE_MMAP in gcconfig.h.)
+You may want to reverse this decisions if you use -DREDIRECT_MALLOC=...
+
+
+SOLARIS THREADS:
+
+The collector must be compiled with -DGC_SOLARIS_THREADS (thr_ functions)
+or -DGC_SOLARIS_PTHREADS (pthread_ functions) to be thread safe.
+It is also essential that gc.h be included in files that call thr_create,
+thr_join, thr_suspend, thr_continue, or dlopen.  Gc.h macro defines
+these to also do GC bookkeeping, etc.  Gc.h must be included with
+one or both of these macros defined, otherwise
+these replacements are not visible.
+A collector built in this way way only be used by programs that are
+linked with the threads library.
+
+In this mode, the collector contains various workarounds for older Solaris
+bugs.  Mostly, these should not be noticeable unless you look at system
+call traces.  However, it cannot protect a guard page at the end of
+a thread stack.  If you know that you will only be running Solaris2.5
+or later, it should be possible to fix this by compiling the collector
+with -DSOLARIS23_MPROTECT_BUG_FIXED.
+
+Since 5.0 alpha5, dlopen disables collection temporarily,
+unless USE_PROC_FOR_LIBRARIES is defined.  In some unlikely cases, this
+can result in unpleasant heap growth.  But it seems better than the
+race/deadlock issues we had before.
+
+If solaris_threads are used on an X86 processor with malloc redirected to
+GC_malloc, it is necessary to call GC_thr_init explicitly before forking the
+first thread.  (This avoids a deadlock arising from calling GC_thr_init
+with the allocation lock held.)
+
+It appears that there is a problem in using gc_cpp.h in conjunction with
+Solaris threads and Sun's C++ runtime.  Apparently the overloaded new operator
+is invoked by some iostream initialization code before threads are correctly
+initialized.  As a result, call to thr_self() in garbage collector
+initialization  segfaults.  Currently the only known workaround is to not
+invoke the garbage collector from a user defined global operator new, or to
+have it invoke the garbage-collector's allocators only after main has started.
+(Note that the latter requires a moderately expensive test in operator
+delete.)
+
+Hans-J. Boehm
+(The above contains my personal opinions, which are probably not shared
+by anyone else.)
diff --git a/gc/doc/README.uts b/gc/doc/README.uts
new file mode 100644
index 0000000..6be4966
--- /dev/null
+++ b/gc/doc/README.uts
@@ -0,0 +1,2 @@
+Alistair Crooks supplied the port.  He used Lexa C version 2.1.3 with
+-Xa to compile.
diff --git a/gc/doc/README.win32 b/gc/doc/README.win32
new file mode 100644
index 0000000..417281d
--- /dev/null
+++ b/gc/doc/README.win32
@@ -0,0 +1,149 @@
+The collector has at various times been compiled under Windows 95 & NT,
+with the original Microsoft SDK, with Visual C++ 2.0, 4.0, and 6, with
+the GNU win32 environment, with Borland 4.5, and recently with
+Watcom C.  It is likely that some of these have been broken in the
+meantime.  Patches are appreciated.
+
+It runs under both win32s and win32, but with different semantics.
+Under win32, all writable pages outside of the heaps and stack are
+scanned for roots.  Thus the collector sees pointers in DLL data
+segments.  Under win32s, only the main data segment is scanned.
+(The main data segment should always be scanned.  Under some
+versions of win32s, other regions may also be scanned.)
+Thus all accessible objects should be accessible from local variables
+or variables in the main data segment.  Alternatively, other data
+segments (e.g. in DLLs) may be registered with the collector by
+calling GC_init() and then GC_register_root_section(a), where
+a is the address of some variable inside the data segment.  (Duplicate
+registrations are ignored, but not terribly quickly.)
+
+(There are two reasons for this.  We didn't want to see many 16:16
+pointers.  And the VirtualQuery call has different semantics under
+the two systems, and under different versions of win32s.)
+
+The collector test program "gctest" is linked as a GUI application,
+but does not open any windows.  Its output appears in the file
+"gc.log".  It may be started from the file manager.  The hour glass
+cursor may appear as long as it's running.  If it is started from the
+command line, it will usually run in the background.  Wait a few
+minutes (a few seconds on a modern machine) before you check the output.
+You should see either a failure indication or a "Collector appears to
+work" message.
+
+The cord test program has not been ported (but should port
+easily).  A toy editor (cord/de.exe) based on cords (heavyweight
+strings represented as trees) has been ported and is included.
+It runs fine under either win32 or win32S.  It serves as an example
+of a true Windows application, except that it was written by a
+nonexpert Windows programmer.  (There are some peculiarities
+in the way files are displayed.  The <cr> is displayed explicitly
+for standard DOS text files.  As in the UNIX version, control
+characters are displayed explicitly, but in this case as red text.
+This may be suboptimal for some tastes and/or sets of default
+window colors.)
+
+In general -DREDIRECT_MALLOC is unlikely to work unless the
+application is completely statically linked.
+
+For Microsoft development tools, rename NT_MAKEFILE as
+MAKEFILE.  (Make sure that the CPU environment variable is defined
+to be i386.)  In order to use the gc_cpp.h C++ interface, all
+client code should include gc_cpp.h.
+
+Clients may need to define GC_NOT_DLL before including gc.h, if the
+collector was built as a static library (as it normally is in the
+absence of thread support).
+
+For GNU-win32, use the regular makefile, possibly after uncommenting
+the line "include Makefile.DLLs".  The latter should be necessary only
+if you want to package the collector as a DLL.  The GNU-win32 port is
+believed to work only for b18, not b19, probably dues to linker changes
+in b19.  This is probably fixable with a different definition of
+DATASTART and DATAEND in gcconfig.h.
+
+For Borland tools, use BCC_MAKEFILE.  Note that
+Borland's compiler defaults to 1 byte alignment in structures (-a1),
+whereas Visual C++ appears to default to 8 byte alignment (/Zp8).
+The garbage collector in its default configuration EXPECTS AT
+LEAST 4 BYTE ALIGNMENT.  Thus the BORLAND DEFAULT MUST
+BE OVERRIDDEN.  (In my opinion, it should usually be anyway.
+I expect that -a1 introduces major performance penalties on a
+486 or Pentium.)  Note that this changes structure layouts.  (As a last
+resort, gcconfig.h can be changed to allow 1 byte alignment.  But
+this has significant negative performance implications.)
+The Makefile is set up to assume Borland 4.5.  If you have another
+version, change the line near the top.  By default, it does not
+require the assembler.  If you do have the assembler, I recommend
+removing the -DUSE_GENERIC.
+
+There is some support for incremental collection.  This is
+currently pretty simple-minded.  Pages are protected.  Protection
+faults are caught by a handler installed at the bottom of the handler
+stack.  This is both slow and interacts poorly with a debugger.
+Whenever possible, I recommend adding a call to
+GC_enable_incremental at the last possible moment, after most
+debugging is complete.  Unlike the UNIX versions, no system
+calls are wrapped by the collector itself.  It may be necessary
+to wrap ReadFile calls that use a buffer in the heap, so that the
+call does not encounter a protection fault while it's running.
+(As usual, none of this is an issue unless GC_enable_incremental
+is called.)
+
+Note that incremental collection is disabled with -DSMALL_CONFIG.
+
+James Clark has contributed the necessary code to support win32 threads.
+Use NT_THREADS_MAKEFILE (a.k.a gc.mak) instead of NT_MAKEFILE
+to build this version.  Note that this requires some files whose names
+are more than 8 + 3 characters long.  Thus you should unpack the tar file
+so that long file names are preserved.  To build the garbage collector
+test with VC++ from the command line, use
+
+nmake /F ".\gc.mak" CFG="gctest - Win32 Release"
+
+This requires that the subdirectory gctest\Release exist.
+The test program and DLL will reside in the Release directory.
+
+This version relies on the collector residing in a dll.
+
+This version currently supports incremental collection only if it is
+enabled before any additional threads are created.
+Version 4.13 attempts to fix some of the earlier problems, but there
+may be other issues.  If you need solid support for win32 threads, you
+might check with Geodesic Systems.  Their collector must be licensed,
+but they have invested far more time in win32-specific issues.
+
+Hans
+
+Ivan V. Demakov's README for the Watcom port:
+
+The collector has been compiled with Watcom C 10.6 and 11.0.
+It runs under win32, win32s, and even under msdos with dos4gw
+dos-extender. It should also run under OS/2, though this isn't
+tested. Under win32 the collector can be built either as dll
+or as static library.
+
+Note that all compilations were done under Windows 95 or NT.
+For unknown reason compiling under Windows 3.11 for NT (one
+attempt has been made) leads to broken executables.
+
+Incremental collection is not supported.
+
+cord is not ported.
+
+Before compiling you may need to edit WCC_MAKEFILE to set target
+platform, library type (dynamic or static), calling conventions, and
+optimization options.
+
+To compile the collector and testing programs use the command:
+    wmake -f WCC_MAKEFILE
+
+All programs using gc should be compiled with 4-byte alignment.
+For further explanations on this see comments about Borland.
+
+If gc compiled as dll, the macro ``GC_DLL'' should be defined before
+including "gc.h" (for example, with -DGC_DLL compiler option). It's
+important, otherwise resulting programs will not run.
+
+Ivan Demakov (email: ivan@tgrad.nsk.su)
+
+