https://llvm.org/bugs/show_bug.cgi?id=25640
Bug ID: 25640
Summary: -Wpessimizing-move false positive for return value of
statement expression
Product: clang
Version: 3.7
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Frontend
Assignee: unassignedclangb...@nondot.org
Reporter: su...@fb.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
The following code generates a -Wpessimizing-move violation:
```
#include <memory>
#include <utility>
class C {};
void f() {
auto c = ({auto c1 = std::make_unique<C>(); std::move(c1);});
}
1.cpp:5:47: error: moving a local object in a return statement prevents copy
elision [-Werror,-Wpessimizing-move]
auto c = ({auto c1 = std::make_unique<C>(); std::move(c1);});
^
1.cpp:5:47: note: remove std::move call here
auto c = ({auto c1 = std::make_unique<C>(); std::move(c1);});
^~~~~~~~~~ ~
```
When `std::move` is removed, it becomes a syntax error:
```
1.cpp:5:47: error: call to deleted constructor of 'std::unique_ptr<C,
std::default_delete<C> >'
auto c = ({auto c1 = std::make_unique<C>(); c1;});
^~
.../unique_ptr.h:356:7: note: 'unique_ptr' has been explicitly marked deleted
here
unique_ptr(const unique_ptr&) = delete;
^
1 error generated.
```
clang --version
clang version 3.8.0 (trunk 251726)
Target: x86_64-unknown-linux-gnu
Thread model: posix
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