Why is clang defining NULL as __null ??

Clang Frontend Using Clang
#1

I have a .cpp file which has usage of NULL at several places. When I try to compile this cpp file for Android/x86 platform using clang++ on Windows machine + standalone tool chain, I am running into “expected expression” error at the places where NULL is used. I find the definition of NULL in stddef.h of clang headers provided by Android NDK as below.

#if defined(__need_NULL)
#undef NULL
#ifdef __cplusplus
#  if !defined(__MINGW32__) && !defined(_MSC_VER)
#    define NULL __null
#  else
#    define NULL 0
#  endif
#else
#  define NULL ((void*)0)
#endif

As far as I know, __null is specific to GNU compiler. In my case both _MSC_VER and __MINGW32__ are undefined because I am compiling for Android platform using clang++ and standalone tool chain. So it is hitting into define NULL __null. Since clang++ has no clue of what __null is, it is resulting into “expected expression” error.

My question is, why is clang using macros(like __null) provided by GNU compiler? Or am I missing something here?

Could somebody please help me understand. Thanks

#2

clang generally also understands __null (for the same reasons GCC does - to provide better diagnostics when using NULL in non-pointer contexts). See, for example, this warning (not an error): https://godbolt.org/z/KvdW7a

Can’t say I know much about the NDK or what version of clang it has, what flags you might be passing, or why else it might be having trouble with __null, unfortunately.