[libc][hdrgen] macro_name/macro_value duplicates defines from libc/include/llvm-libc-macros/*-macros.h

[nickdesaulniers]

I just noticed that our generated dlfcn.h has:

#include "llvm-libc-macros/dlfcn-macros.h"
#define RTLD_LAZY

and my editor was warning me about RTLD_LAZY (and friends being redefined). I noticed because building llvm against our headers was producing error: expecting expression in llvm/ code that used these preprocessor defines.

libc/include/dlfcn.yaml uses macro_name+macro_value to define these, but then we ALSO have them listed in libc/include/llvm-libc-macros/dlfcn-macros.h.

If we were just going to define them in one but not the other, rather than redefining them, which would we choose?

I think we should just stick with libc/include/llvm-libc-macros/dlfcn-macros.h. I don't see currently what the point of macro_value/macro_name is. We could do something fancy with generating special values at build time, but FWICT we're not doing that at all right now.

Did I miss something, or should we just drop the macro_name/macro_value feature from hdrgen and hard code these #defines in the corresponding libc/include/llvm-libc-macros/*-macros.h?

cc @michaelrj-google @frobtech

[llvmbot]

@llvm/issue-subscribers-libc

Author: Nick Desaulniers (nickdesaulniers)

I just noticed that our generated dlfcn.h has: ```c #include "llvm-libc-macros/dlfcn-macros.h" #define RTLD_LAZY ``` and my editor was warning me about `RTLD_LAZY` (and friends being redefined). I noticed because building llvm against our headers was producing `error: expecting expression` in llvm/ code that used these preprocessor defines.

libc/include/dlfcn.yaml uses macro_name+macro_value to define these, but then we ALSO have them listed in libc/include/llvm-libc-macros/dlfcn-macros.h.

If we were just going to define them in one, but not the other, which would we choose?

I think we should just stick with libc/include/llvm-libc-macros/dlfcn-macros.h. I don't see currently what the point of macro_value/macro_name is. We could do something fancy with generating special values at build time, but FWICT we're not doing that at all right now.

Did I miss something, or should we just drop the macro_name/macro_value feature from hdrgen and hard code these #defines in the corresponding libc/include/llvm-libc-macros/*-macros.h?

cc @michaelrj-google @frobtech

[nickdesaulniers]

Oh, this is similar to feedback I left in #123265 (had forgotten about that).