Force an error when a function prototype is missing

If someone understands the stochastic process whereby GCC decides to
apply this function or not, please let me know.

diff --git a/configure.ac b/configure.ac
index 0bb57b6624e5a79860732b159c391858c06c0cbf..8cd1f77e9794f4b9b61288d30cffe76c650f8b8b 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -933,7 +933,7 @@ if test "${ac_cv_c_ntohl_sys_param_h}" != "no"; then
 fi
 CFLAGS="${CFLAGS_save}"
 
-RDC_PROG_CC_WFLAGS([all extra sign-compare undef pointer-arith bad-function-cast cast-align write-strings missing-prototypes volatile-register-var])
+RDC_PROG_CC_WFLAGS([all extra sign-compare undef pointer-arith bad-function-cast cast-align write-strings missing-prototypes volatile-register-var error-implicit-function-declaration])
 RDC_PROG_CC_FLAGS_IFELSE([-pipe])
 
 dnl Check for various optimization flags