[llvm-branch-commits] [cfe-branch] r295234 - Merging r295150:

[Hans Wennborg via llvm-branch-commits]

Author: hans
Date: Wed Feb 15 14:51:59 2017
New Revision: 295234

URL: http://llvm.org/viewvc/llvm-project?rev=295234&view=rev
Log:
Merging r295150:
------------------------------------------------------------------------
r295150 | ahatanak | 2017-02-14 21:15:28 -0800 (Tue, 14 Feb 2017) | 13 lines

[Sema] Disallow returning a __block variable via a move.

r274291 made changes to prefer calling a move constructor to calling a
copy constructor when returning from a function. This caused programs to
crash when a __block variable in the heap was moved out and used later.

This commit fixes the bug by disallowing moving out of __block variables
implicitly.

rdar://problem/28181080

Differential Revision: https://reviews.llvm.org/D29908

------------------------------------------------------------------------

Modified:
    cfe/branches/release_40/   (props changed)
    cfe/branches/release_40/lib/Sema/SemaStmt.cpp
    cfe/branches/release_40/test/SemaObjCXX/blocks.mm

Propchange: cfe/branches/release_40/
------------------------------------------------------------------------------
--- svn:mergeinfo (original)
+++ svn:mergeinfo Wed Feb 15 14:51:59 2017
@@ -1,4 +1,4 @@
 /cfe/branches/type-system-rewrite:134693-134817
-/cfe/trunk:291850,291853,291865,291871,291877,291879,291881,291907,291955,291963-291964,292032,292052,292183,292194,292247,292265,292497,292555,292558-292559,292561,292590,292800,292847,292874,292991,293043,293134,293360,293369,293596,293678,293787,294008,294800,294855,295149
+/cfe/trunk:291850,291853,291865,291871,291877,291879,291881,291907,291955,291963-291964,292032,292052,292183,292194,292247,292265,292497,292555,292558-292559,292561,292590,292800,292847,292874,292991,293043,293134,293360,293369,293596,293678,293787,294008,294800,294855,295149-295150
 /cfe/trunk/test:170344
 /cfe/trunk/test/SemaTemplate:126920

Modified: cfe/branches/release_40/lib/Sema/SemaStmt.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/branches/release_40/lib/Sema/SemaStmt.cpp?rev=295234&r1=295233&r2=295234&view=diff
==============================================================================
--- cfe/branches/release_40/lib/Sema/SemaStmt.cpp (original)
+++ cfe/branches/release_40/lib/Sema/SemaStmt.cpp Wed Feb 15 14:51:59 2017
@@ -2743,15 +2743,17 @@ bool Sema::isCopyElisionCandidate(QualTy
   // ...automatic...
   if (!VD->hasLocalStorage()) return false;
 
+  // Return false if VD is a __block variable. We don't want to implicitly move
+  // out of a __block variable during a return because we cannot assume the
+  // variable will no longer be used.
+  if (VD->hasAttr<BlocksAttr>()) return false;
+
   if (AllowParamOrMoveConstructible)
     return true;
 
   // ...non-volatile...
   if (VD->getType().isVolatileQualified()) return false;
 
-  // __block variables can't be allocated in a way that permits NRVO.
-  if (VD->hasAttr<BlocksAttr>()) return false;
-
   // Variables with higher required alignment than their type's ABI
   // alignment cannot use NRVO.
   if (!VD->getType()->isDependentType() && VD->hasAttr<AlignedAttr>() &&

Modified: cfe/branches/release_40/test/SemaObjCXX/blocks.mm
URL: http://llvm.org/viewvc/llvm-project/cfe/branches/release_40/test/SemaObjCXX/blocks.mm?rev=295234&r1=295233&r2=295234&view=diff
==============================================================================
--- cfe/branches/release_40/test/SemaObjCXX/blocks.mm (original)
+++ cfe/branches/release_40/test/SemaObjCXX/blocks.mm Wed Feb 15 14:51:59 2017
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -fblocks -Wno-objc-root-class %s
+// RUN: %clang_cc1 -fsyntax-only -verify -fblocks -Wno-objc-root-class -std=c++11 %s
 @protocol NSObject;
 
 void bar(id(^)(void));
@@ -144,3 +144,17 @@ namespace DependentReturn {
 
   template void f<X>(X);
 }
+
+namespace MoveBlockVariable {
+struct B0 {
+};
+
+struct B1 { // expected-note 2 {{candidate constructor (the implicit}}
+  B1(B0&&); // expected-note {{candidate constructor not viable}}
+};
+
+B1 test_move() {
+  __block B0 b;
+  return b; // expected-error {{no viable conversion from returned value of type 'MoveBlockVariable::B0' to function return type 'MoveBlockVariable::B1'}}
+}
+}