From 86ced61713098b13d58f24f4dfd0806dddaeb20c Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Wed, 15 Feb 2017 20:51:59 +0000 Subject: 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 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_40@295234 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Sema/SemaStmt.cpp | 8 +++++--- test/SemaObjCXX/blocks.mm | 16 +++++++++++++++- 2 files changed, 20 insertions(+), 4 deletions(-) diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp index a8832e9a1c..390e1b52c8 100644 --- a/lib/Sema/SemaStmt.cpp +++ b/lib/Sema/SemaStmt.cpp @@ -2743,15 +2743,17 @@ bool Sema::isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD, // ...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()) 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()) return false; - // Variables with higher required alignment than their type's ABI // alignment cannot use NRVO. if (!VD->getType()->isDependentType() && VD->hasAttr() && diff --git a/test/SemaObjCXX/blocks.mm b/test/SemaObjCXX/blocks.mm index 09d614d372..3f901cc0a8 100644 --- a/test/SemaObjCXX/blocks.mm +++ b/test/SemaObjCXX/blocks.mm @@ -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); } + +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'}} +} +} -- cgit v1.2.3