Add -Wno-tautological-compare to the standard compile flags, if that
is accepted.  With XCode 5.5.1 -Wtautological-compare appears to come
as standard, and it generates a lot of mostly useless noise.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14136 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/Makefile.all.am b/Makefile.all.am
index b3b344a..0d30ed5 100644
--- a/Makefile.all.am
+++ b/Makefile.all.am
@@ -105,6 +105,7 @@
 	-Wstrict-prototypes \
 	-Wmissing-declarations \
 	@FLAG_W_NO_FORMAT_ZERO_LENGTH@ \
+	@FLAG_W_NO_TAUTOLOGICAL_COMPARE@ \
 	-fno-strict-aliasing \
 	-fno-builtin
 
diff --git a/configure.ac b/configure.ac
index e87a2e4..c91ea94 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1727,6 +1727,25 @@
 CFLAGS=$safe_CFLAGS
 
 
+# does this compiler support -Wno-tautological-compare ?
+
+AC_MSG_CHECKING([if gcc accepts -Wno-tautological-compare])
+
+safe_CFLAGS=$CFLAGS
+CFLAGS="-Wno-tautological-compare"
+
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ ]], [[
+  return 0;
+]])], [
+AC_SUBST([FLAG_W_NO_TAUTOLOGICAL_COMPARE], [-Wno-tautological-compare])
+AC_MSG_RESULT([yes])
+], [
+AC_SUBST([FLAG_W_NO_TAUTOLOGICAL_COMPARE], [])
+AC_MSG_RESULT([no])
+])
+CFLAGS=$safe_CFLAGS
+
+
 # does this compiler support -Wno-nonnull ?
 
 AC_MSG_CHECKING([if gcc accepts -Wno-nonnull])