From 3ed4d1cbaad763c103771bdefb8b986a08f165fc Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Tue, 18 Jun 2013 17:51:51 +0000
Subject: [PATCH] PR14503: Don't assert if a constexpr constructor temploid
 instantiates to a constructor that does not initialize all members, and that
 constructor is used to initialize a global.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184211 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticASTKinds.td     |  2 ++
 lib/AST/ExprConstant.cpp                      |  5 +++++
 .../CXX/dcl.dcl/dcl.spec/dcl.constexpr/p4.cpp | 20 +++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/include/clang/Basic/DiagnosticASTKinds.td b/include/clang/Basic/DiagnosticASTKinds.td
index 06aca52c63..f560069189 100644
--- a/include/clang/Basic/DiagnosticASTKinds.td
+++ b/include/clang/Basic/DiagnosticASTKinds.td
@@ -38,6 +38,8 @@ def note_constexpr_nonliteral : Note<
 def note_constexpr_non_global : Note<
   "%select{pointer|reference}0 to %select{|subobject of }1"
   "%select{temporary|%3}2 is not a constant expression">;
+def note_constexpr_uninitialized : Note<
+  "subobject of type %0 is not initialized">;
 def note_constexpr_array_index : Note<"cannot refer to element %0 of "
   "%select{array of %2 elements|non-array object}1 in a constant expression">;
 def note_constexpr_float_arithmetic : Note<
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 86dcbd04e7..72f1c21ee6 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -1132,6 +1132,11 @@ static bool CheckLiteralType(EvalInfo &Info, const Expr *E,
 /// check that the expression is of literal type.
 static bool CheckConstantExpression(EvalInfo &Info, SourceLocation DiagLoc,
                                     QualType Type, const APValue &Value) {
+  if (Value.isUninit()) {
+    Info.Diag(DiagLoc, diag::note_constexpr_uninitialized) << Type;
+    return false;
+  }
+
   // Core issue 1454: For a literal constant expression of array or class type,
   // each subobject of its value shall have been initialized by a constant
   // expression.
diff --git a/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p4.cpp b/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p4.cpp
index 8a4fa42f00..708c259d5b 100644
--- a/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p4.cpp
+++ b/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p4.cpp
@@ -314,3 +314,23 @@ namespace CtorLookup {
   constexpr C::C(const C&) = default;
   constexpr C::C(C&) = default; // expected-error {{not constexpr}}
 }
+
+namespace PR14503 {
+  template<typename> struct V {
+    union {
+      int n;
+      struct {
+        int x,
+            y;
+      };
+    };
+    constexpr V() : x(0) {}
+  };
+
+  // The constructor is still 'constexpr' here, but the result is not intended
+  // to be a constant expression. The standard is not clear on how this should
+  // work.
+  constexpr V<int> v; // expected-error {{constant expression}} expected-note {{subobject of type 'int' is not initialized}}
+
+  constexpr int k = V<int>().x; // FIXME: ok?
+}
-- 
2.40.0