[PATCH] D26376: Undef stdatomic.h macro definitions that are defining functions provided in libc++ <atomic>

[Mehdi AMINI via Phabricator via cfe-commits]

mehdi_amini added a comment.

In https://reviews.llvm.org/D26376#597614, @mclow.lists wrote:

> More info - The following code:
>
>   #include <stdatomic.h>
>   int main () {}
>   
>
> fails to compile on either gcc 6.2 (locally), gcc 7 head (online compiler) or MSVC (online compiler).


Interesting, that lead me to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60932 which describes the issue I believe.

One of the example is that we should guarantee ABI compatibility between C and C++ for such code:

  #ifdef __cplusplus
  #include <atomic>
  using namespace std;
  #else
  #include <stdatomic.h>
  #endif
  
  struct s {
    atomic_int i;
  };

Do you know if we're providing this guarantee today?

In https://reviews.llvm.org/D26376#613186, @EricWF wrote:

> Yeah this seems like a configuration that simply can't be supported. I'm not sure if this patch is a great idea.


OK, let's abandon this then!


https://reviews.llvm.org/D26376