Hey, On Mon, Jun 04, 2012 at 12:08:20PM -0600, Eric Blake wrote:
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 (LIBVIRT_COMPILE_WARNINGS): Squelch _FORTIFY_SOURCE when needed to avoid glibc #warnings. ---
Pushing under the build-breaker rule.
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 5527bff..a91d69f 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -102,8 +102,12 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ # Silence certain warnings in gnulib, and use improved glibc headers AC_DEFINE([lint], [1], [Define to 1 if the compiler is checking for lint.]) - 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 __OPTIMIZE__ + # define _FORTIFY_SOURCE 2 + #endif + ])
This is not causing an actual issue while compiling libvirt, but __OPTIMIZE__ is not defined when using -O0, which causes a warning with -Wundef I've tested this with $ gcc --version gcc (GCC) 4.7.0 20120507 (Red Hat 4.7.0-5) $ gcc -c -Wundef -O0 test.c #if __OPTIMIZE__ #warning if __OPTIMIZE__ #endif #ifdef __OPTIMIZE__ #warning ifdef __OPTIMIZE #endif Using a #ifdef would be more correct: diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 index a91d69f..0ea7276 100644 --- a/m4/virt-compile-warnings.m4 +++ b/m4/virt-compile-warnings.m4 @@ -104,7 +104,7 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ [Define to 1 if the compiler is checking for lint.]) AH_VERBATIM([FORTIFY_SOURCE], [/* Enable compile-time and run-time bounds-checking, and some warnings. */ - #if __OPTIMIZE__ + #ifdef __OPTIMIZE__ # define _FORTIFY_SOURCE 2 #endif ]) [ (or doing #ifdef __OPTIMIZE__ #if __OPTIMIZE .... if __OPTIMIZE__ was set to 0 with -O0 with some gcc/libc versions) Christophe