Add a warning for questionable va_args usage.

llvm-svn: 68435

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -1464,6 +1464,8 @@ def err_va_start_used_in_non_variadic_function : Error<
   "'va_start' used in function with fixed args">;
 def warn_second_parameter_of_va_start_not_last_named_argument : Warning<
   "second parameter of 'va_start' not last named argument">;
+def warn_va_arg_with_qualified_va_list : Warning<
+  "va_arg applied to va_list type %0 with unexpected qualifiers">;
 def err_first_argument_to_va_arg_not_of_type_va_list : Error<
   "first argument to 'va_arg' is of type %0 and not 'va_list'">;
 

clang/lib/Sema/SemaExpr.cpp

@@ -4726,11 +4726,18 @@ Sema::OwningExprResult Sema::ActOnVAArg(SourceLocation BuiltinLoc,
 
   AssignConvertType ConvResult = 
     CheckAssignmentConstraints(VaListType, E->getType());
-  if (ConvResult != Compatible &&
-      ConvResult != CompatiblePointerDiscardsQualifiers)
+  switch (ConvResult) {
+  case Compatible: break;  // Everything good.
+  case CompatiblePointerDiscardsQualifiers:
+    Diag(E->getLocStart(), diag::warn_va_arg_with_qualified_va_list)
+      << E->getType() << E->getSourceRange();
+    break;
+
+  default:
     return ExprError(Diag(E->getLocStart(),
                          diag::err_first_argument_to_va_arg_not_of_type_va_list)
       << E->getType() << E->getSourceRange());
+  }
 
   // FIXME: Check that type is complete/non-abstract
   // FIXME: Warn if a non-POD type is passed in.

clang/test/Sema/varargs-x86-64.c

@@ -0,0 +1,8 @@
+// RUN: clang-cc -fsyntax-only -verify %s -triple x86_64-apple-darwin9
+
+// rdar://6726818
+void f1() {
+  const __builtin_va_list args2;
+  (void)__builtin_va_arg(args2, int); // expected-warning {{va_arg applied to va_list type 'struct __va_list_tag const *' with unexpected qualifiers}}
+}
+

clang/test/Sema/varargs.c

@@ -61,9 +61,3 @@ void f7(int a, ...) {
   __builtin_va_end(ap);
 }
 
-// rdar://6726818
-void f8() {
-  const __builtin_va_list args2;
-  (void)__builtin_va_arg(args2, int);
-}
-