Followup to r15323. Cannot use AC_GCC_WARNING_SUBST to detect

whether -Wformat-security is supported. Special handling is needed.

gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2  accepts -Wformat-security
without -Wformat being present on the command line. Other GCC
versions will issue a warning if -Wformat is missing. r15323
adds -Werror to AC_GCC_WARNING_SUBST and therefore turns that
warning into an error.  With the consequence that
-Wformat-security appears to be unsupported -- a false conclusion.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15331

diff --git a/configure.ac b/configure.ac
index 57dbfa7cd0f505258af85d4e85f9160327bd13cf..e3afe8074791c890732a3795127a8800cf882679 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1738,12 +1738,27 @@ AC_GCC_WARNING_SUBST_NO([static-local-in-inline], [FLAG_W_NO_STATIC_LOCAL_IN_INL
 AC_GCC_WARNING_SUBST([write-strings], [FLAG_W_WRITE_STRINGS])
 AC_GCC_WARNING_SUBST([empty-body], [FLAG_W_EMPTY_BODY])
 AC_GCC_WARNING_SUBST([format], [FLAG_W_FORMAT])
-AC_GCC_WARNING_SUBST([format-security], [FLAG_W_FORMAT_SECURITY])
 AC_GCC_WARNING_SUBST([cast-qual], [FLAG_W_CAST_QUAL])
 AC_GCC_WARNING_SUBST([old-style-declaration], [FLAG_W_OLD_STYLE_DECLARATION])
 AC_GCC_WARNING_SUBST([ignored-qualifiers], [FLAG_W_IGNORED_QUALIFIERS])
 AC_GCC_WARNING_SUBST([missing-parameter-type], [FLAG_W_MISSING_PARAMETER_TYPE])
 
+# Does this compiler support -Wformat-security ?
+# Special handling is needed, because certain GCC versions require -Wformat
+# being present if -Wformat-security is given. Otherwise a warning is issued.
+# However, AC_GCC_WARNING_SUBST will stick in -Werror (see r15323 for rationale).
+# And with that the warning will be turned into an error with the result
+# that -Wformat-security is believed to be unsupported when in fact it is.
+AC_MSG_CHECKING([if gcc accepts -Wformat-security])
+safe_CFLAGS=$CFLAGS
+CFLAGS="-Wformat -Wformat-security -Werror"
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]], [[;]])], [
+AC_SUBST([FLAG_W_FORMAT_SECURITY], [-Wformat-security])
+AC_MSG_RESULT([yes])], [
+AC_SUBST([FLAG_W_FORMAT_SECURITY], [])
+AC_MSG_RESULT([no])])
+CFLAGS=$safe_CFLAGS
+
 # does this compiler support -Wextra or the older -W ?
 
 AC_MSG_CHECKING([if gcc accepts -Wextra or -W])