[libvirt] [PATCH 1/2] build: allow building with newer glibc-headers and -O0

Fix copied from libvirt, commit by Eric Blake. glibc 2.15 (on Fedora 17) coupled with explicit disabling of optimization during development dies a painful death: /usr/include/features.h:314:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp] 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 | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index d403587..913abca 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -84,8 +84,12 @@ AC_DEFUN([LIBVIRT_DESIGNER_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. */ + #if defined __OPTIMIZE__ && __OPTIMIZE__ + # define _FORTIFY_SOURCE 2 + #endif + ]) # Extra special flags dnl -fstack-protector stuff passes gl_WARN_ADD with gcc -- 1.7.11.4