1 files changed, 16 insertions, 0 deletions
diff --git a/gcc/c-common.c b/gcc/c-common.c
index 7b27ba0..b843df2 100644
--- a/gcc/c-common.c
+++ b/gcc/c-common.c
@@ -6284,4 +6284,20 @@ check_missing_format_attribute (tree ltype, tree rtype)
     return false;
 }
 
+/* Subscripting with type char is likely to lose on a machine where
+   chars are signed.  So warn on any machine, but optionally.  Don't
+   warn for unsigned char since that type is safe.  Don't warn for
+   signed char because anyone who uses that must have done so
+   deliberately. Furthermore, we reduce the false positive load by
+   warning only for non-constant value of type char.  */
+
+void
+warn_array_subscript_with_type_char (tree index)
+{
+  if (TYPE_MAIN_VARIANT (TREE_TYPE (index)) == char_type_node
+      && TREE_CODE (index) != INTEGER_CST)
+    warning (OPT_Wchar_subscripts, "array subscript has type %<char%>");
+}
+
+
 #include "gt-c-common.h"