From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Thu, 6 Jun 2013 08:19:16 +0000 (+0000)
Subject: When a static storage duration temporary appears in a constant expression, it
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=f69dd33cfc0b1f2a6c88d10951dbd29c4dc806c2;p=clang

When a static storage duration temporary appears in a constant expression, it
must be initialized by a constant expression (not just a core constant
expression), because we're going to emit it as a global. Core issue for this is
pending.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183388 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 19eaf55ba4..d94efc1341 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -4099,12 +4099,17 @@ bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
     Result.set(E, Info.CurrentCall->Index);
   }
 
+  QualType Type = Inner->getType();
+
   // Materialize the temporary itself.
-  if (!EvaluateInPlace(*Value, Info, Result, Inner))
+  if (!EvaluateInPlace(*Value, Info, Result, Inner) ||
+      (E->getStorageDuration() == SD_Static &&
+       !CheckConstantExpression(Info, E->getExprLoc(), Type, *Value))) {
+    *Value = APValue();
     return false;
+  }
 
   // Adjust our lvalue to refer to the desired subobject.
-  QualType Type = Inner->getType();
   for (unsigned I = Adjustments.size(); I != 0; /**/) {
     --I;
     switch (Adjustments[I].Kind) {
diff --git a/test/SemaCXX/constant-expression-cxx11.cpp b/test/SemaCXX/constant-expression-cxx11.cpp
index 3a460c93af..fb2e6a32ee 100644
--- a/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/test/SemaCXX/constant-expression-cxx11.cpp
@@ -363,6 +363,16 @@ static_assert(&b4 != &b2, "");
 // Proposed DR: copy-elision doesn't trigger lifetime extension.
 constexpr B b5 = B{ {0}, {0} }; // expected-error {{constant expression}} expected-note {{reference to temporary}} expected-note {{here}}
 
+namespace NestedNonStatic {
+  // Proposed DR: for a reference constant expression to refer to a static
+  // storage duration temporary, that temporary must itself be initialized
+  // by a constant expression (a core constant expression is not enough).
+  struct A { int &&r; };
+  struct B { A &&a; };
+  constexpr B a = { A{0} }; // ok
+  constexpr B b = { A(A{0}) }; // expected-error {{constant expression}} expected-note {{reference to temporary}} expected-note {{here}}
+}
+
 }
 
 constexpr int strcmp_ce(const char *p, const char *q) {