Hi,
Bastian Blank wrote:
It's obviously buggy to emit a warning on standards-mandated behaviour!
I know you can turn this warning off with -Wno-unknown-pragmas, but
that's not something you want to be doing in production code.
Please show the part of the standard. A compiler may produce warnings
without reason.
Was the section I quoted in my original bug report not sufficient?
Paragraph 7.6.1.2 of C99 says [again]:
"If part of a program tests floating-point status flags, sets
floating-point control modes, or runs under non-default mode settings,
but was translated with the state for the FENV_ACCESS pragma "off", *the
behaviour is undefined*." [emphasis mine]
These are things that many correct programs will want to do. For
example, SuSv3 has this to say about pow():
"An application wishing to check for error situations should set errno
to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
occurred."[1]
Gcc as-is, will encourage (quite strongly, since may people will compile
with -Wall, +/- -Werror) users to write code that calls feclearexcept()
and suchlike without using #pragma STDC FENV_ACCESS ON first. This is
undefined behaviour, according to C99! It seems clear to me that this is
a bug in gcc.
Regards,
Matthew
[1] http://www.opengroup.org/onlinepubs/009695399/functions/pow.html
--
To UNSUBSCRIBE, email to [EMAIL PROTECTED]
with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
