[libvirt] [PATCH] build: silence some compiler warnings from gnulib

[Eric Blake]

Gnulib claims that there are some classes of warnings that are
worth enabling during development, but where silencing those
warnings causes code bloat that is not necessary in an optimized
build.  The code bloat to silence the warnings is only enabled
by -Dlint.  Follow the lead of coreutils in setting up -Dlint
whenever full warnings are requested.

* m4/virt-compile-warnings.m4 (LIBVIRT_COMPILE_WARNINGS): Add
-Dlint, and move _FORTIFY_SOURCE to config.h instead of CFLAGS.
---

In particular, see this gnulib thread, where Dan Berrange complained
about a warning present on a mingw cross-compile:
https://lists.gnu.org/archive/html/bug-gnulib/2012-01/msg00184.html

 m4/virt-compile-warnings.m4 |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4
index ba388aa..3a428c3 100644
--- a/m4/virt-compile-warnings.m4
+++ b/m4/virt-compile-warnings.m4
@@ -100,8 +100,13 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
         gl_WARN_ADD([-Wframe-larger-than=4096])
         dnl gl_WARN_ADD([-Wframe-larger-than=256])

+        # 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])
+
         # Extra special flags
-        gl_WARN_ADD([-Wp,-D_FORTIFY_SOURCE=2])
         dnl -fstack-protector stuff passes gl_WARN_ADD with gcc
         dnl on Mingw32, but fails when actually used
         case $host in
-- 
1.7.7.5