build: error on implicit function declaration

This patch modifies gcc options to error in case of implicit
declaration. Bug #612 has shown this kind of bugs can be very
costly.

diff --git a/configure.ac b/configure.ac
index a0c7af72e43893e60cee86e5351622f14d4e8a44..c8236539ae867d5b57ee99953314853e8bc69241 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -45,7 +45,7 @@ AC_INIT(configure.ac)
 
     if test "$gccvernum" -ge "400"; then
             dnl gcc 4.0 or later
-            CFLAGS="$CFLAGS -Wextra"
+            CFLAGS="$CFLAGS -Wextra -Werror=implicit-function-declaration"
     else
             CFLAGS="$CFLAGS -W"
     fi