Fix va_arg bug noticed by Eli, __builtin_va_arg is not an l-value

designating an object.

llvm-svn: 64371

2 files changed, 9 insertions, 1 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 95a6a349f31..7b06a3c1ce6 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -565,7 +565,7 @@ Expr::isLvalueResult Expr::isLvalue(ASTContext &Ctx) const {
   case PredefinedExprClass:
     return LV_Valid;
   case VAArgExprClass:
-    return LV_Valid;
+    return LV_NotObjectType;
   case CXXDefaultArgExprClass:
     return cast<CXXDefaultArgExpr>(this)->getExpr()->isLvalue(Ctx);
   case CXXConditionDeclExprClass:
diff --git a/clang/test/Sema/varargs.c b/clang/test/Sema/varargs.c
index ae21c208eb8..b340177f9c5 100644
--- a/clang/test/Sema/varargs.c
+++ b/clang/test/Sema/varargs.c
@@ -52,3 +52,11 @@ foo(__builtin_va_list authors, ...) {
   __builtin_va_end (authors);
 }
 
+void f7(int a, ...) {
+  __builtin_va_list ap;
+  __builtin_va_start(ap, a);
+  // FIXME: This error message is sub-par.
+  __builtin_va_arg(ap, int) = 1; // expected-error {{non-object type 'int' is not assignable}}
+  int *x = &__builtin_va_arg(ap, int); // expected-error {{address expression must be an lvalue or a function designator}}
+  __builtin_va_end(ap);
+}