Enable stricter C99 warnings

Fedora is considering moving all its packages to C99 and enabling
stricter C99 warnings. OCaml has already moved to a compiler requiring
C11 features, let's enable these warnings on GCC-compatible compilers.

Some of the warnings on the following article are already covered by
-Wall and -Werror.

Reference: [Modernizing Fedora's C code][1].

[1]: https://lwn.net/Articles/913505/

1 files changed, 2 insertions, 1 deletions

diff --git a/configure b/configure
index 487f66a95e..57981c8a32 100755
--- a/configure
+++ b/configure
@@ -13656,7 +13656,8 @@ case $ocaml_cv_cc_vendor in #(
   *) :
     outputobj='-o '
   warn_error_flag='-Werror'
-  cc_warnings='-Wall' ;;
+  cc_warnings="-Wall -Wint-conversion -Wstrict-prototypes \
+-Wold-style-definition" ;;
 esac
 
 case $enable_warn_error,true in #(