-Wchar-subscripts should not warn for unsigned char subscripts. Fixes PR4978.

llvm-svn: 81776

clang/lib/Sema/SemaExpr.cpp

@@ -1809,7 +1809,9 @@ Sema::ActOnArraySubscriptExpr(Scope *S, ExprArg Base, SourceLocation LLoc,
     return ExprError(Diag(LLoc, diag::err_typecheck_subscript_not_integer)
                      << IndexExpr->getSourceRange());
 
-  if (IndexExpr->getType()->isCharType() && !IndexExpr->isTypeDependent())
+  QualType IndexTy = Context.getCanonicalType(IndexExpr->getType());
+  if ((IndexTy == Context.CharTy || IndexTy == Context.SignedCharTy)
+      && !IndexExpr->isTypeDependent())
     Diag(LLoc, diag::warn_subscript_is_char) << IndexExpr->getSourceRange();
 
   // C99 6.5.2.1p1: "shall have type "pointer to *object* type". Similarly,

clang/test/Sema/warn-char-subscripts.c

@@ -29,3 +29,36 @@ void t5() {
   int *array = 0;
   int val = array[returnsChar()]; // expected-warning{{array subscript is of type 'char'}}
 }
+
+void t6() {
+  int array[1] = { 0 };
+  signed char subscript = 0;
+  int val = array[subscript]; // expected-warning{{array subscript is of type 'char'}}
+}
+
+void t7() {
+  int array[1] = { 0 };
+  unsigned char subscript = 0;
+  int val = array[subscript]; // no warning for unsigned char
+}
+
+typedef char CharTy;
+void t8() {
+  int array[1] = { 0 };
+  CharTy subscript = 0;
+  int val = array[subscript]; // expected-warning{{array subscript is of type 'char'}}
+}
+
+typedef signed char SignedCharTy;
+void t9() {
+  int array[1] = { 0 };
+  SignedCharTy subscript = 0;
+  int val = array[subscript]; // expected-warning{{array subscript is of type 'char'}}
+}
+
+typedef unsigned char UnsignedCharTy;
+void t10() {
+  int array[1] = { 0 };
+  UnsignedCharTy subscript = 0;
+  int val = array[subscript]; // no warning for unsigned char
+}