[libvirt] [libvirt-glib] build: allow building with newer glibc-headers and -O0

Commit log and autoconf snippet written by Eric Blake for libvirt. glibc 2.15 (on Fedora 17) coupled with explicit disabling of optimization during development dies a painful death: In file included from /usr/include/limits.h:27:0, from /usr/lib/gcc/x86_64-redhat-linux/4.7.0/include/limits.h:169,. from /usr/lib/gcc/x86_64-redhat-linux/4.7.0/include/syslimits.h:7, from /usr/lib/gcc/x86_64-redhat-linux/4.7.0/include/limits.h:34, from util/bitmap.c:26: /usr/include/features.h:314:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp] cc1: all warnings being treated as errors Work around this by only conditionally defining _FORTIFY_SOURCE, in the case where glibc can actually use it. The trick is using AH_VERBATIM instead of AC_DEFINE. * m4/virt-compile-warnings.m4 (LIBOSINFO_COMPILE_WARNINGS): Squelch _FORTIFY_SOURCE when needed to avoid glibc #warnings. --- m4/virt-compile-warnings.m4 | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index de542cc..99d214e 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -84,8 +84,13 @@ AC_DEFUN([LIBVIRT_GLIB_COMPILE_WARNINGS],[ gl_WARN_ADD([-Wframe-larger-than=4096]) # Use improved glibc headers - AC_DEFINE([_FORTIFY_SOURCE], [2], - [enable compile-time and run-time bounds-checking, and some warnings]) + AH_VERBATIM([FORTIFY_SOURCE], + [/* Enable compile-time and run-time bounds-checking, and some warnings, + without upsetting newer glibc. */ + #if defined __OPTIMIZE__ && __OPTIMIZE__ + # define _FORTIFY_SOURCE 2 + #endif + ]) # Extra special flags dnl -fstack-protector stuff passes gl_WARN_ADD with gcc -- 1.7.10.2