curl-compilers.m4: enable missing-variable-declarations clang warning

It usually warns when forgetting to declare TU-local variables static.

Closes https://github.com/curl/curl/pull/1578

diff --git a/m4/curl-compilers.m4 b/m4/curl-compilers.m4
index 7d53953c91d48f327775378adbb93fa84ebd0855..9efe2ae2350202a63ecc76a6b13db299e62903b8 100644 (file)
--- a/m4/curl-compilers.m4
+++ b/m4/curl-compilers.m4
@@ -892,6 +892,11 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
             tmp_CFLAGS="$tmp_CFLAGS -Wshift-sign-overflow"
           fi
           #
+          dnl Only clang 3.2 or later
+          if test "$compiler_num" -ge "302"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wmissing-variable-declarations"
+          fi
+          #
           dnl Only clang 3.6 or later
           if test "$compiler_num" -ge "306"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wdouble-promotion"