curl-compilers.m4: enable vla warning for clang

Previously, that warning was only implicitly active in C90 mode.
Enable it unconditionally as already done for GCC.

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

diff --git a/m4/curl-compilers.m4 b/m4/curl-compilers.m4
index 88e9d67ba2b5da05745174af26e3abc7267e7b72..5860f946efc7b90c34a244ac66996afcc6b0d65f 100644 (file)
--- a/m4/curl-compilers.m4
+++ b/m4/curl-compilers.m4
@@ -882,6 +882,11 @@ AC_DEFUN([CURL_SET_COMPILER_WARNING_OPTS], [
             tmp_CFLAGS="$tmp_CFLAGS -Wunused"
           fi
           #
+          dnl Only clang 2.8 or later
+          if test "$compiler_num" -ge "208"; then
+            tmp_CFLAGS="$tmp_CFLAGS -Wvla"
+          fi
+          #
           dnl Only clang 2.9 or later
           if test "$compiler_num" -ge "209"; then
             tmp_CFLAGS="$tmp_CFLAGS -Wshift-sign-overflow"