Missing C11 conditional feature macros

[nemequ]

According to § 6.10.8.3 of the C11 spec, __STDC_NO_ATOMICS__ should be defined in C11 mode when stdatomic.h is not available, as is the case for emscripten.

Testing is easy:

#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L) && !defined(__STDC_NO_ATOMICS__)
#include <stdatomic.h>
#endif

I use variants of that snippet in several places. I'm working around the issue with an additional && !defined(__EMSCRIPTEN__), but that's obviously sub-optimal.

You should probably also define __STDC_NO_THREADS__ until threads.h provides a complete implementation (i.e., until mtx_t and cnd_t are implemented).

[paulshapiro]

This would be very useful for me. @kripken any idea on the level of effort on this? I may be able to help with a bit of guidance.

[kripken]

The best place to add that define is in tools/shared.py (around where we define -D__EMSCRIPTEN__ etc.).

However, it seems like we could provide that header - we do have threads and atomics support, in particular pthreads works. Maybe it needs clang integration, though - if so, I'm not sure of the status of that.

[stale]

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