<bits/features.h> setting of __STDC_IEC_559__ not universally accurate

[Joseph S. Myers]

On Mon, 28 Mar 2005, Mark Mitchell wrote:

> Ideally, the software floating-point emulation would indeed provide full IEC
> 559 conformance.  And, as the CONFORMANCE file indicates, __STDC_IEC_559__
> should really be defined by the compiler, so that it is set throughout the
> entire translation unit.

It and other such macros should be set throughout the translation unit - 
to a value depending on the library, not just the compiler, though passing 
some of the flags included in -ffast-math should probably disable defining 
this macro.  (This is most significant for __STDC_ISO_10646__, the value 
of which may depend on the precise library version.)  My proposal for such 
definitions is to have a separate header <stdc-macros.h> which defines 
these macros - but does not include <features.h> itself - which the 
compiler would preinclude at the start of each translation unit if it 
exists, and which <features.h> would include for the sake of older 
compilers.

-- 
Joseph S. Myers
joseph@codesourcery.com