1 files changed, 17 insertions, 1 deletions

diff --git a/config.m4 b/config.m4
index f73dfe8..9cb8969 100644
--- a/config.m4
+++ b/config.m4
@@ -27,4 +27,20 @@ if test "$PHP_SUHOSIN7_DEBUG" != "no"; then
         AC_DEFINE(SUHOSIN7_DEBUG, 1, [Whether to enable suhosin7 debugging])
 fi
 
-CFLAGS="$CFLAGS -std=c11"
+AC_MSG_CHECKING([for C11 support with -std=c11])
+old_CFLAGS="$CFLAGS"
+CFLAGS+=" -std=c11"
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[])],[AC_MSG_RESULT([yes])],[
+        AC_MSG_RESULT([no])
+        CFLAGS="$old_CFLAGS"
+        echo "===== WARNING ============================================"
+        echo "  Suhosin7 is written in C11, but your compiler lacks C11"
+        echo "  support. Trying C99 instead, but compiling may fail."
+        echo "=========================================================="
+        AC_MSG_CHECKING([for C99 support with -std=c99])
+        CFLAGS+=" -std=c99"
+        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[])],[AC_MSG_RESULT([yes])],[
+                AC_MSG_RESULT([no])
+                CFLAGS="$old_CFLAGS"
+        ])
+])