[Bug libc/6981] New: __STDC_IEC_559__ should not be defined unconditionally

["vincent+libc at vinc17 dot org" <sourceware-bugzilla at sourceware dot org>]

__STDC_IEC_559__ is unconditionally defined as 1 in "/usr/include/features.h".
On some platforms, this is incorrect. In particular, if FLT_EVAL_METHOD is 1 or
2, it doesn't make sense to define __STDC_IEC_559__ as this contradicts the
bindings defined in Annex F of the ISO C standard.

I suggest to define __STDC_IEC_559__ only if FLT_EVAL_METHOD is 0 (probably test
__FLT_EVAL_METHOD__).

Even this test would not be sufficient with GCC, as it systematically contracts
expressions (in particular on PowerPC and IA-64, which have a FMA), which is
against the support of Annex F.

-- 
           Summary: __STDC_IEC_559__ should not be defined unconditionally
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: vincent+libc at vinc17 dot org
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=6981

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