build: enable -Wundef warnings

Now that we've fixed all of them, enable them by default if the compiler
supports it.

Signed-off-by: Ruben Kerkhof <ruben@rubenkerkhof.com>

diff --git a/configure.ac b/configure.ac
index fe389ebb35c827953016c8752f9f4c5a97d83ab1..628e0c8afc1dbce65b0f70cb5cc97219155bd040 100755 (executable)
--- a/configure.ac
+++ b/configure.ac
@@ -295,6 +295,7 @@ AC_C_FLAG([-Wmissing-declarations])
 AC_C_FLAG([-Wpointer-arith])
 AC_C_FLAG([-Wbad-function-cast])
 AC_C_FLAG([-Wwrite-strings])
+AC_C_FLAG([-Wundef])
 if test "$enable_gcc_ultra_verbose" = "yes" ; then
   AC_C_FLAG([-Wcast-qual])
   AC_C_FLAG([-Wstrict-prototypes])