1 files changed, 63 insertions, 11 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 467fb82b8d0..19eaf55ba43 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -1001,6 +1001,10 @@ static bool IsGlobalLValue(APValue::LValueBase B) {
     const CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
     return CLE->isFileScope() && CLE->isLValue();
   }
+  case Expr::MaterializeTemporaryExprClass:
+    // A materialized temporary might have been lifetime-extended to static
+    // storage duration.
+    return cast<MaterializeTemporaryExpr>(E)->getStorageDuration() == SD_Static;
   // A string literal has static storage duration.
   case Expr::StringLiteralClass:
   case Expr::PredefinedExprClass:
@@ -1182,7 +1186,10 @@ const ValueDecl *GetLValueBaseDecl(const LValue &LVal) {
 }
 
 static bool IsLiteralLValue(const LValue &Value) {
-  return Value.Base.dyn_cast<const Expr*>() && !Value.CallIndex;
+  if (Value.CallIndex)
+    return false;
+  const Expr *E = Value.Base.dyn_cast<const Expr*>();
+  return E && !isa<MaterializeTemporaryExpr>(E);
 }
 
 static bool IsWeakLValue(const LValue &Value) {
@@ -2279,11 +2286,44 @@ CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E, AccessKinds AK,
     const Expr *Base = LVal.Base.dyn_cast<const Expr*>();
 
     if (!Frame) {
-      Info.Diag(E);
-      return CompleteObject();
-    }
+      if (const MaterializeTemporaryExpr *MTE =
+              dyn_cast<MaterializeTemporaryExpr>(Base)) {
+        assert(MTE->getStorageDuration() == SD_Static &&
+               "should have a frame for a non-global materialized temporary");
+
+        // Per C++1y [expr.const]p2:
+        //  an lvalue-to-rvalue conversion [is not allowed unless it applies to]
+        //   - a [...] glvalue of integral or enumeration type that refers to
+        //     a non-volatile const object [...]
+        //   [...]
+        //   - a [...] glvalue of literal type that refers to a non-volatile
+        //     object whose lifetime began within the evaluation of e.
+        //
+        // C++11 misses the 'began within the evaluation of e' check and
+        // instead allows all temporaries, including things like:
+        //   int &&r = 1;
+        //   int x = ++r;
+        //   constexpr int k = r;
+        // Therefore we use the C++1y rules in C++11 too.
+        const ValueDecl *VD = Info.EvaluatingDecl.dyn_cast<const ValueDecl*>();
+        const ValueDecl *ED = MTE->getExtendingDecl();
+        if (!(BaseType.isConstQualified() &&
+              BaseType->isIntegralOrEnumerationType()) &&
+            !(VD && VD->getCanonicalDecl() == ED->getCanonicalDecl())) {
+          Info.Diag(E, diag::note_constexpr_access_static_temporary, 1) << AK;
+          Info.Note(MTE->getExprLoc(), diag::note_constexpr_temporary_here);
+          return CompleteObject();
+        }
 
-    BaseVal = &Frame->Temporaries[Base];
+        BaseVal = Info.Ctx.getMaterializedTemporaryValue(MTE, false);
+        assert(BaseVal && "got reference to unevaluated temporary");
+      } else {
+        Info.Diag(E);
+        return CompleteObject();
+      }
+    } else {
+      BaseVal = &Frame->Temporaries[Base];
+    }
 
     // Volatile temporary objects cannot be accessed in constant expressions.
     if (BaseType.isVolatileQualified()) {
@@ -3940,6 +3980,8 @@ public:
 //  * Any Expr, with a CallIndex indicating the function in which the temporary
 //    was evaluated, for cases where the MaterializeTemporaryExpr is missing
 //    from the AST (FIXME).
+//  * A MaterializeTemporaryExpr that has static storage duration, with no
+//    CallIndex, for a lifetime-extended temporary.
 // plus an offset in bytes.
 //===----------------------------------------------------------------------===//
 namespace {
@@ -4045,9 +4087,19 @@ bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
     if (!EvaluateIgnoredValue(Info, CommaLHSs[I]))
       return false;
 
+  // A materialized temporary with static storage duration can appear within the
+  // result of a constant expression evaluation, so we need to preserve its
+  // value for use outside this evaluation.
+  APValue *Value;
+  if (E->getStorageDuration() == SD_Static) {
+    Value = Info.Ctx.getMaterializedTemporaryValue(E, true);
+    Result.set(E);
+  } else {
+    Value = &Info.CurrentCall->Temporaries[E];
+    Result.set(E, Info.CurrentCall->Index);
+  }
+
   // Materialize the temporary itself.
-  APValue *Value = &Info.CurrentCall->Temporaries[E];
-  Result.set(E, Info.CurrentCall->Index);
   if (!EvaluateInPlace(*Value, Info, Result, Inner))
     return false;
 
@@ -7608,10 +7660,10 @@ void Expr::EvaluateForOverflow(const ASTContext &Ctx,
   }
 }
 
- bool Expr::EvalResult::isGlobalLValue() const {
-   assert(Val.isLValue());
-   return IsGlobalLValue(Val.getLValueBase());
- }
+bool Expr::EvalResult::isGlobalLValue() const {
+  assert(Val.isLValue());
+  return IsGlobalLValue(Val.getLValueBase());
+}
 
 
 /// isIntegerConstantExpr - this recursive routine will test if an expression is