[Bug middle-end/34678] Optimization generates incorrect code with -frounding-math option (#pragma STDC FENV_ACCESS not implemented)

[vincent-gcc at vinc17 dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34678

--- Comment #30 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Nick Maclaren from comment #29)
> It is not an "explicit definition of BEHAVIOR" (my emphasis),

The pragma is just a directive. It has no additional behavior, so that there is
nothing else to define.

> >Note that the C standard doesn't explicitly say how a source file as a sequence
> >of bytes is to be interpreted as a sequence of character, so that if you just
      ^^^^^
> > restrict to the C standard, everything is undefined.
> 
> Yes, it does - it's implementation-defined in 5.1.1.2 Translation phases,
> paragraph 1.1:
> 
>     Physical source file multibyte characters are mapped, in an
                           ^^^^^^^^^^^^^^^^^^^^
Read again. I'm talking of a sequence of bytes. What your quoting is about a
sequence of multibyte characters. The interpretation of the sequences of bytes
as a sequence of multibyte characters is not defined.

> You imply that you are also relying on some other standards or
> specifications.

Not other standards, just the implementation.