From a39154ecac549b4115902a99f6e6c77b1a9e09ad Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sun, 7 Jun 2015 22:25:22 +0200
Subject: [PATCH] Fix autoconf check for function attributes.

GCC warns when a function attribute has no effect. The autoconf check
turns warnings about attributes into errors, therefore thinking that
they did not work. The reason was that the test function returned void,
which is not suitable for checking both __malloc__ and
__warn_unused_result__.
---
 m4/attribute.m4 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/m4/attribute.m4 b/m4/attribute.m4
index 6a8f5558..9d673e96 100644
--- a/m4/attribute.m4
+++ b/m4/attribute.m4
@@ -9,8 +9,8 @@ AC_DEFUN([tinc_ATTRIBUTE],
     CFLAGS="$CFLAGS -Wall -Werror"
     AC_COMPILE_IFELSE(
       [AC_LANG_SOURCE(
-        [void test(void) __attribute__ (($1));
-	 void test(void) { return; }
+        [void *test(void) __attribute__ (($1));
+	 void *test(void) { return (void *)0; }
 	],
        )],
        [tinc_cv_attribute_$1=yes],