added a note regarding what to do when you get the `stddef.h not found`.

testscript is still WIP.

1 files changed, 4 insertions, 0 deletions

diff --git a/README.md b/README.md
index e251032..51ff3ea 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,10 @@ For an up-to-date list, you can run `cgrep --help` or look at the man page.
 `cgrep` is a clang tool, so it will accept all valid clang command line options.
 
 ## Known Issues
+`cgrep` complains that it cannot find `stddef.h` or some other similar header. If that happens to you , it's because cgrep can't find the clang built-in headers. run `llvm-config --libdir`, then head on to `clang`. Inside that directory you should see one(or maybe more) llvm/clang versions. Pick the one you used to build cgrep against. Inside that directory there will be a directory named `include`. Pass that to cgrep any way you see fit.<br/>
+Alternatively, `$(llvm-config --libdir)/clang/$(llvm-config --version)/include` should give the path cgrep needs to include. If you build your llvm/clang from upstream, this might not work. SVN bulds will have the svn string attached to the version number.<br/>
+You could,for example, use `--extra-arg=-I/usr/lib/llvm-9/lib/clang/9.0.0/include` to call cgrep or you could just alias `cgrep` to `cgrep --extra-arg=-I/usr/lib/llvm-9/lib/clang/9.0.0/include`.<br/>
+
 `cgrep`, replaces the clang diagnosticConsumer with a simple one that only tells you there are erros during the compilation. You can get the normal clang output using the `--clangdiag` switch. The decision was made to declutter the output generated by cgrep.
 
 ## License