From 8c92b87cd0c34c68f1025f39405e7b783074430b Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Sun, 14 Dec 2014 08:40:47 +0000
Subject: [PATCH] AST: Limit zero-sized constexpr behavior to array types

Restricting this "extension" to array types maximizes our standards
conformance while not miscompiling real-world programs.

llvm-svn: 224215
---
 clang/lib/AST/ExprConstant.cpp                   | 4 +++-
 clang/test/SemaCXX/constant-expression-cxx11.cpp | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 417f7931df47..ad36e76bea45 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -1426,7 +1426,9 @@ static bool isZeroSized(const LValue &Value) {
   const ValueDecl *Decl = GetLValueBaseDecl(Value);
   if (Decl && isa<VarDecl>(Decl)) {
     QualType Ty = Decl->getType();
-    return Ty->isIncompleteType() || Decl->getASTContext().getTypeSize(Ty) == 0;
+    if (Ty->isArrayType())
+      return Ty->isIncompleteType() ||
+             Decl->getASTContext().getTypeSize(Ty) == 0;
   }
   return false;
 }
diff --git a/clang/test/SemaCXX/constant-expression-cxx11.cpp b/clang/test/SemaCXX/constant-expression-cxx11.cpp
index cf317950c772..dbb1255ef1c8 100644
--- a/clang/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx11.cpp
@@ -1960,6 +1960,7 @@ namespace PR21786 {
   extern void (*start[])();
   extern void (*end[])();
   static_assert(&start != &end, ""); // expected-error {{constant expression}}
+  static_assert(&start != nullptr, "");
 
   struct Foo;
   struct Bar {
@@ -1967,7 +1968,7 @@ namespace PR21786 {
     static const Foo y;
   };
   static_assert(&Bar::x != nullptr, "");
-  static_assert(&Bar::x != &Bar::y, ""); // expected-error {{constant expression}}
+  static_assert(&Bar::x != &Bar::y, "");
 }
 
 namespace PR21859 {