http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678
--- Comment #27 from Nick Maclaren <nmm1 at cam dot ac.uk> --- On Jan 14 2014, vincent-gcc at vinc17 dot net wrote: > >http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678 > >> What "explicit definition of behavior" is there for the case when >> STDC FENV_ACCESS is set to "on" but __STDC_IEC_559__ is not set to one? > >The behavior is defined. The standard says, e.g. for C99: > >7.6.1 The FENV_ACCESS pragma > >The FENV_ACCESS pragma provides a means to inform the implementation when a >program might access the floating-point environment to test floating-point >status flags or run under non-default floating-point control modes. I suggest looking up the word "explicit" in a dictionary. Unless __STDC_IEC_559__ is set to 1, what modes and flags exist (and, even more importantly) what there semantics are) is at best implicit and more realistically unspecified - see footnote 204 for a clear statement of that. Have you ever implemented a C system for an architecture with non-IEEE arithmetic but with modes and flags? Because I have, and I have used several others. >> As there is none, it is undefined behaviour. gcc can therefore do >> whatever it likes. > >No. You are quite simply wrong. Regards, Nick Maclaren.
