[PATCH] D34695: _Float16 preprocessor macro definitions

[Roger Ferrer Ibanez via Phabricator via cfe-commits]

rogfer01 added inline comments.


================
Comment at: lib/Headers/float.h:137
 
+#ifdef __STDC_WANT_IEC_60559_TYPES_EXT__
+#  define FLT16_MANT_DIG  __FLT16_MANT_DIG__
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scanon wrote:
> rogfer01 wrote:
> > My understanding is that, given that we support TS18661-2 by default, this macro should be predefined by clang and then there is no need to protect these macros.
> > 
> > You may want to add a test for this in `test/Preprocessor/init.c`.
> Where do you see that the `__STDC_WANT_IEC_60559_TYPES_EXT__` macro should be predefined by clang?
Hi Steve,

certainly you're right, the TS says

> The new identifiers added to C11 library headers by this part of ISO/IEC TS-18661 are defined or declared by their respective headers only if `__STDC_WANT_IEC_60559_TYPES_EXT__` is defined as a macro at the point in the source file where the appropriate header is first included.

so (if I read this right) these identifiers are only available if such macro is defined when including `float.h`. 

Can I assume from your comment that someone else should define it? Perhaps the `float.h` header itself, some other file in the C-library implementation or the user of the compiler via some `-D__STDC_WANT_IEC_60559_TYPES_EXT__`, but not be predefined by the compiler? If this is the case, then the macros still have to be guarded conditionally (as they were in the original patch).

Does this make sense? Thanks.


https://reviews.llvm.org/D34695