DR1213: element access on an array xvalue or prvalue produces an xvalue. In the

latter case, a temporary array object is materialized, and can be
lifetime-extended by binding a reference to the member access. Likewise, in an
array-to-pointer decay, an rvalue array is materialized before being converted
into a pointer.

This caused IR generation to stop treating file-scope array compound literals
as having static storage duration in some cases in C++; that has been rectified
by modeling such a compound literal as an lvalue. This also improves clang's
compatibility with GCC for those cases.

llvm-svn: 288654

1 files changed, 4 insertions, 3 deletions

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 3937aad..c21dbc1 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -5971,9 +5971,10 @@ performReferenceExtension(Expr *Init,
       if (CE->getSubExpr()->isGLValue())
         Init = CE->getSubExpr();
 
-    // FIXME: Per DR1213, subscripting on an array temporary produces an xvalue.
-    // It's unclear if binding a reference to that xvalue extends the array
-    // temporary.
+    // Per the current approach for DR1299, look through array element access
+    // when performing lifetime extension.
+    if (auto *ASE = dyn_cast<ArraySubscriptExpr>(Init))
+      Init = ASE->getBase();
   } while (Init != Old);
 
   if (MaterializeTemporaryExpr *ME = dyn_cast<MaterializeTemporaryExpr>(Init)) {