[Bug target/40411] -std=c99 does not enable c99 mode in Solaris C library

["redi at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40411

--- Comment #19 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-12-26 21:52:07 UTC ---
(In reply to comment #17)
> For this reason, I would find it bad if "gcc -std=c99" or "gcc -std=gnu99"
> would cause values-xpg6.o to be included in the link. Please close this
> issue as "Won't fix". Programs which wish to have POSIX compliant behaviour
> of system functions can use GNU gnulib; it doesn't rely on values-xpg6.o.

I don't entirely agree with this line of reasoning. If the system provides a
POSIX compliant C library it's reasonable to want to use it and users will want
some way to tel the compiler to do so. Whether using it is enabled via -std or
not, linking to values-xpg6.o can cause unexpected behaviour for applications
or shared objects.

It does seem reasonable to expect -std=c99 to enable C99 features if the system
supports them, and similarly for -std=c++0x