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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
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_40@295234
91177308-0d34-0410-b5e6-
96231b3b80d8
// ...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>() &&
-// 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));
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'}}
+}
+}