[libvirt] [PATCH] build: fix build at -O2 on rawhide

I had previously tested commit 059d746 with -O intentionally omitted from my CFLAGS; but that means that I missed out on this warning from gcc 4.6.2 when optimizations are enabled: util/buf.c: In function 'virBufferGetIndent': util/buf.c:86:1: error: function might be candidate for attribute 'pure' [-Werror=suggest-attribute=pure] While it is probably a good idea to add the attributes and silence this warning, it's also invasive; 'make -k' found more than 75 such complaints. And it doesn't help that gcc 4.6.2 is still buggy (coreutils reported a case where gcc 4.6.2 incorrectly suggested marking a function pure that incremented a global variable; fixed in gcc 4.7). So the best fix for now is to disable the warning. It also doesn't help that I stumbled across another problem - gcc documents that -Wsuggest-attribute=pure only warns if you use -O, or if you use -fipa-pure-const. But in practice, when I omitted -O but added -fipa-pure-const, the warnings are fickle - I got warnings for simple compilation that disappeared when I also added -fPIC. And the way libtool compiles things is with -fPIC first, then without -fPIC but with errors sent to /dev/null - which meant that without disabling -Wsuggest-attribute=pure, I got a compile error with no message. :( See http://debbugs.gnu.org/cgi/bugreport.cgi?bug=10197 * m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Silence -Wsuggest-attribute warnings for now. --- Pushing under the build-breaker rule. m4/virt-compile-warnings.m4 | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index 213b3db..34a89c9 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -116,2 +116,2 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ gl_WARN_ADD([-fdiagnostics-show-option]) gl_WARN_ADD([-funit-at-a-time]) + # Need -fipa-pure-const in order to make -Wsuggest-attribute=pure + # fire even without -O. + gl_WARN_ADD([-fipa-pure-const]) + # We should eventually enable this, but right now there are at + # least 75 functions triggering warnings. + gl_WARN_ADD([-Wno-suggest-attribute=pure]) + gl_WARN_ADD([-Wno-suggest-attribute=const]) + if test "$enable_compile_warnings" = "error" then gl_WARN_ADD([-Werror]) -- 1.7.7.3