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diff --git a/gc/gc_cpp.h b/gc/gc_cpp.h new file mode 100644 index 0000000..ad7df5d --- /dev/null +++ b/gc/gc_cpp.h @@ -0,0 +1,290 @@ +#ifndef GC_CPP_H +#define GC_CPP_H +/**************************************************************************** +Copyright (c) 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. +**************************************************************************** + +C++ Interface to the Boehm Collector + + John R. Ellis and Jesse Hull + Last modified on Mon Jul 24 15:43:42 PDT 1995 by ellis + +This interface provides access to the Boehm collector. It provides +basic facilities similar to those described in "Safe, Efficient +Garbage Collection for C++", by John R. Elis and David L. Detlefs +(ftp.parc.xerox.com:/pub/ellis/gc). + +All heap-allocated objects are either "collectable" or +"uncollectable". Programs must explicitly delete uncollectable +objects, whereas the garbage collector will automatically delete +collectable objects when it discovers them to be inaccessible. +Collectable objects may freely point at uncollectable objects and vice +versa. + +Objects allocated with the built-in "::operator new" are uncollectable. + +Objects derived from class "gc" are collectable. For example: + + class A: public gc {...}; + A* a = new A; // a is collectable. + +Collectable instances of non-class types can be allocated using the GC +placement: + + typedef int A[ 10 ]; + A* a = new (GC) A; + +Uncollectable instances of classes derived from "gc" can be allocated +using the NoGC placement: + + class A: public gc {...}; + A* a = new (NoGC) A; // a is uncollectable. + +Both uncollectable and collectable objects can be explicitly deleted +with "delete", which invokes an object's destructors and frees its +storage immediately. + +A collectable object may have a clean-up function, which will be +invoked when the collector discovers the object to be inaccessible. +An object derived from "gc_cleanup" or containing a member derived +from "gc_cleanup" has a default clean-up function that invokes the +object's destructors. Explicit clean-up functions may be specified as +an additional placement argument: + + A* a = ::new (GC, MyCleanup) A; + +An object is considered "accessible" by the collector if it can be +reached by a path of pointers from static variables, automatic +variables of active functions, or from some object with clean-up +enabled; pointers from an object to itself are ignored. + +Thus, if objects A and B both have clean-up functions, and A points at +B, B is considered accessible. After A's clean-up is invoked and its +storage released, B will then become inaccessible and will have its +clean-up invoked. If A points at B and B points to A, forming a +cycle, then that's considered a storage leak, and neither will be +collectable. See the interface gc.h for low-level facilities for +handling such cycles of objects with clean-up. + +The collector cannot guarrantee that it will find all inaccessible +objects. In practice, it finds almost all of them. + + +Cautions: + +1. Be sure the collector has been augmented with "make c++". + +2. If your compiler supports the new "operator new[]" syntax, then +add -DOPERATOR_NEW_ARRAY to the Makefile. + +If your compiler doesn't support "operator new[]", beware that an +array of type T, where T is derived from "gc", may or may not be +allocated as a collectable object (it depends on the compiler). Use +the explicit GC placement to make the array collectable. For example: + + class A: public gc {...}; + A* a1 = new A[ 10 ]; // collectable or uncollectable? + A* a2 = new (GC) A[ 10 ]; // collectable + +3. The destructors of collectable arrays of objects derived from +"gc_cleanup" will not be invoked properly. For example: + + class A: public gc_cleanup {...}; + A* a = new (GC) A[ 10 ]; // destructors not invoked correctly + +Typically, only the destructor for the first element of the array will +be invoked when the array is garbage-collected. To get all the +destructors of any array executed, you must supply an explicit +clean-up function: + + A* a = new (GC, MyCleanUp) A[ 10 ]; + +(Implementing clean-up of arrays correctly, portably, and in a way +that preserves the correct exception semantics requires a language +extension, e.g. the "gc" keyword.) + +4. Compiler bugs: + +* Solaris 2's CC (SC3.0) doesn't implement t->~T() correctly, so the +destructors of classes derived from gc_cleanup won't be invoked. +You'll have to explicitly register a clean-up function with +new-placement syntax. + +* Evidently cfront 3.0 does not allow destructors to be explicitly +invoked using the ANSI-conforming syntax t->~T(). If you're using +cfront 3.0, you'll have to comment out the class gc_cleanup, which +uses explicit invocation. + +****************************************************************************/ + +#include "gc.h" + +#ifndef THINK_CPLUS +#define _cdecl +#endif + +#if ! defined( OPERATOR_NEW_ARRAY ) \ + && (__BORLANDC__ >= 0x450 || (__GNUC__ >= 2 && __GNUC_MINOR__ >= 6) \ + || __WATCOMC__ >= 1050) +# define OPERATOR_NEW_ARRAY +#endif + +enum GCPlacement {GC, NoGC, PointerFreeGC}; + +class gc {public: + inline void* operator new( size_t size ); + inline void* operator new( size_t size, GCPlacement gcp ); + inline void operator delete( void* obj ); + +#ifdef OPERATOR_NEW_ARRAY + inline void* operator new[]( size_t size ); + inline void* operator new[]( size_t size, GCPlacement gcp ); + inline void operator delete[]( void* obj ); +#endif /* OPERATOR_NEW_ARRAY */ + }; + /* + Instances of classes derived from "gc" will be allocated in the + collected heap by default, unless an explicit NoGC placement is + specified. */ + +class gc_cleanup: virtual public gc {public: + inline gc_cleanup(); + inline virtual ~gc_cleanup(); +private: + inline static void _cdecl cleanup( void* obj, void* clientData );}; + /* + Instances of classes derived from "gc_cleanup" will be allocated + in the collected heap by default. When the collector discovers an + inaccessible object derived from "gc_cleanup" or containing a + member derived from "gc_cleanup", its destructors will be + invoked. */ + +extern "C" {typedef void (*GCCleanUpFunc)( void* obj, void* clientData );} + +inline void* operator new( + size_t size, + GCPlacement gcp, + GCCleanUpFunc cleanup = 0, + void* clientData = 0 ); + /* + Allocates a collectable or uncollected object, according to the + value of "gcp". + + For collectable objects, if "cleanup" is non-null, then when the + allocated object "obj" becomes inaccessible, the collector will + invoke the function "cleanup( obj, clientData )" but will not + invoke the object's destructors. It is an error to explicitly + delete an object allocated with a non-null "cleanup". + + It is an error to specify a non-null "cleanup" with NoGC or for + classes derived from "gc_cleanup" or containing members derived + from "gc_cleanup". */ + +#ifdef OPERATOR_NEW_ARRAY + +inline void* operator new[]( + size_t size, + GCPlacement gcp, + GCCleanUpFunc cleanup = 0, + void* clientData = 0 ); + /* + The operator new for arrays, identical to the above. */ + +#endif /* OPERATOR_NEW_ARRAY */ + +/**************************************************************************** + +Inline implementation + +****************************************************************************/ + +inline void* gc::operator new( size_t size ) { + return GC_MALLOC( size );} + +inline void* gc::operator new( size_t size, GCPlacement gcp ) { + if (gcp == GC) + return GC_MALLOC( size ); + else if (gcp == PointerFreeGC) + return GC_MALLOC_ATOMIC( size ); + else + return GC_MALLOC_UNCOLLECTABLE( size );} + +inline void gc::operator delete( void* obj ) { + GC_FREE( obj );} + + +#ifdef OPERATOR_NEW_ARRAY + +inline void* gc::operator new[]( size_t size ) { + return gc::operator new( size );} + +inline void* gc::operator new[]( size_t size, GCPlacement gcp ) { + return gc::operator new( size, gcp );} + +inline void gc::operator delete[]( void* obj ) { + gc::operator delete( obj );} + +#endif /* OPERATOR_NEW_ARRAY */ + + +inline gc_cleanup::~gc_cleanup() { + GC_REGISTER_FINALIZER_IGNORE_SELF( GC_base(this), 0, 0, 0, 0 );} + +inline void gc_cleanup::cleanup( void* obj, void* displ ) { + ((gc_cleanup*) ((char*) obj + (ptrdiff_t) displ))->~gc_cleanup();} + +inline gc_cleanup::gc_cleanup() { + GC_finalization_proc oldProc; + void* oldData; + void* base = GC_base( (void *) this ); + if (0 == base) return; + GC_REGISTER_FINALIZER_IGNORE_SELF( + base, cleanup, (void*) ((char*) this - (char*) base), + &oldProc, &oldData ); + if (0 != oldProc) { + GC_REGISTER_FINALIZER_IGNORE_SELF( base, oldProc, oldData, 0, 0 );}} + +inline void* operator new( + size_t size, + GCPlacement gcp, + GCCleanUpFunc cleanup, + void* clientData ) +{ + void* obj; + + if (gcp == GC) { + obj = GC_MALLOC( size ); + if (cleanup != 0) + GC_REGISTER_FINALIZER_IGNORE_SELF( + obj, cleanup, clientData, 0, 0 );} + else if (gcp == PointerFreeGC) { + obj = GC_MALLOC_ATOMIC( size );} + else { + obj = GC_MALLOC_UNCOLLECTABLE( size );}; + return obj;} + + +#ifdef OPERATOR_NEW_ARRAY + +inline void* operator new[]( + size_t size, + GCPlacement gcp, + GCCleanUpFunc cleanup, + void* clientData ) +{ + return ::operator new( size, gcp, cleanup, clientData );} + +#endif /* OPERATOR_NEW_ARRAY */ + + +#endif /* GC_CPP_H */ + |