[libvirt] [PATCHv3 1/3] build: Check for broken GCC -Wlogical-op in configure
Some older versions of GCC report a false positive on code like
char * haystack, needle;
strchr(haystack, needle);
Added an extra check in configure.ac which will
#define BROKEN_GCC_WLOGICALOP 1
in this case, allowing to special handle "offending" code.
Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com>
---
configure.ac | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/configure.ac b/configure.ac
index bf32f95..dbcd079 100644
--- a/configure.ac
+++ b/configure.ac
@@ -254,6 +254,29 @@ AC_CHECK_TYPE([struct ifreq],
#include <net/if.h>
]])
+dnl Check whether strchr(s, char variable) causes a bogus compile warning
+dnl which is the case with a certain range of GCC versions
+AC_MSG_CHECKING([whether GCC -Wlogical-op is broken])
+
+save_CFLAGS="$CFLAGS"
+CFLAGS="-O2 -Wlogical-op -Werror"
+
+AC_TRY_COMPILE([#include <string.h>],
+ [const char *haystack;
+ char needle;
+ return strchr(haystack, needle) == haystack;],
+ [gcc_false_strchr_warning=no],
+ [gcc_false_strchr_warning=yes])
+
+CFLAGS="$save_CFLAGS"
+
+if test "x$gcc_false_strchr_warning" = xyes; then
+ AC_DEFINE_UNQUOTED([BROKEN_GCC_WLOGICALOP], 1,
+ [GCC -Wlogical-op is reporting false positive on strchr])
+fi
+
+AC_MSG_RESULT([$gcc_false_strchr_warning])
+
dnl Our only use of libtasn1.h is in the testsuite, and can be skipped
dnl if the header is not present. Assume -ltasn1 is present if the
dnl header could be found.
--
1.7.9.5