On Fri, 2011-12-09 at 09:52 -0800, Alan Coopersmith wrote: > On 12/09/11 07:40, Keith Packard wrote: > > On Fri, 09 Dec 2011 07:45:01 -0500, Gaetan Nadon<[email protected]> > > wrote: > > > >> This function is deprecated because it defines -fno-strict-aliasing > >> which alters the code generated by the compiler. If -fno-strict-aliasing > >> is needed, then it should be added explicitly in the module when > >> it is updated to use BASE_CFLAGS. > > > > Does this change the default for this flag? -fno-strict-aliasing is > > needed to preserve compatibility with older code, and I think it should > > probably be on by default until a module owner disables it manually. > > The actual diff is: > -if test "x$GCC" = xyes ; then > - XSERVER_CFLAGS="$XSERVER_CFLAGS -fno-strict-aliasing" > -fi > +XORG_TESTSET_CFLAG([NO_STRICT_ALIASING_CFLAG], [-fno-strict-aliasing]) > +XSERVER_CFLAGS='$(BASE_CFLAGS) $(NO_STRICT_ALIASING_CFLAG)' > > which has the net effect of changing it from hardcoding for gcc to passing > it to any compiler which accepts the flag, so many actually expand usage of > it on non-gcc compilers. >
My understanding is that XORG_TESTSET_CFLAG tests the compiler flag with
the compiler being used. During xserver configuration, I get:
checking if gcc -std=gnu99 supports -fno-strict-aliasing... yes
I expect that the variable will be empty on non gcc compilers but I have
not tested that personally.
# XORG_TESTSET_CFLAG(<variable>, <flag>, [<alternative flag>, ...])
# ---------------
# Minimum version: 1.16.0
#
# Test if the compiler works when passed the given flag as a command
line argument.
# If it succeeds, the flag is appeneded to the given variable. If not,
it tries the
# next flag in the list until there are no more options.
#
# Note that this does not guarantee that the compiler supports the flag
as some
# compilers will simply ignore arguments that they do not understand,
but we do
# attempt to weed out false positives by using
-Werror=unknown-warning-option and
# -Werror=unused-command-line-argument
#
Thanks.
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