Both the compiler and the linker have to accept -fstack-protector

Author: jedisct1

configure.ac

@@ -42,8 +42,20 @@ AS_IF([echo `(uname -s) 2>/dev/null` | $GREP "CYGWIN" > /dev/null], [
   AX_CHECK_LINK_FLAG([-Wl,--nxcompat], [LDFLAGS="$LDFLAGS -Wl,--nxcompat"])
 ], [
   AS_IF([test `(uname -s) 2>/dev/null` = "DragonFly"],
-    [AX_CHECK_COMPILE_FLAG([-fstack-protector], [CFLAGS="$CFLAGS -fstack-protector"])],
-    [AX_CHECK_COMPILE_FLAG([-fstack-protector-all], [CFLAGS="$CFLAGS -fstack-protector-all"])]
+    [
+      AX_CHECK_COMPILE_FLAG([-fstack-protector], [
+        AX_CHECK_LINK_FLAG([-fstack-protector],
+          [CFLAGS="$CFLAGS -fstack-protector"]
+	)
+      ])
+    ],
+    [
+      AX_CHECK_COMPILE_FLAG([-fstack-protector-all], [
+        AX_CHECK_LINK_FLAG([-fstack-protector-all],
+          [CFLAGS="$CFLAGS -fstack-protector-all"]
+	)
+      ])
+    ]
   )
   AS_IF([test "x$ac_compiler_gnu" = "xyes"],[
     AS_IF([$CC --version 2>/dev/null | $GREP "Free Software Foundation" > /dev/null 2>&1],[

m4/ax_check_link_flag.m4

@@ -60,7 +60,8 @@ AC_DEFUN([AX_CHECK_LINK_FLAG],
 AC_CACHE_CHECK([whether the linker accepts $1], CACHEVAR, [
   ax_check_save_flags=$LDFLAGS
   LDFLAGS="$LDFLAGS $4 $1"
-  AC_LINK_IFELSE([AC_LANG_PROGRAM()],
+  AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <stdio.h>]],
+  [[char x[42U];if (fgets(x,1000,stdin)) puts(x)]])],
     [AS_VAR_SET(CACHEVAR,[yes])],
     [AS_VAR_SET(CACHEVAR,[no])])
   LDFLAGS=$ax_check_save_flags])