https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77542
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
CC| |msebor at gcc dot gnu.org
Known to work| |7.3.0, 8.2.0, 9.0
Resolution|--- |FIXED
Known to fail| |5.3.0, 6.4.0
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
After fixing the test in attachment 39608 I get the output below which I think
is what the reporter expected. Resolving as fixed.
$ cat t.C && xg++ -S -Wall t.C
#include <memory>
class Foo {
public:
void close() { }
private:
int foo;
};
struct FooDeleter
{
void operator()(Foo *foo) { foo->close(); }
};
class Test {
public:
typedef std::unique_ptr<Foo, FooDeleter> BindScope;
template <typename... Args>
BindScope bind(Args&&... args) __attribute__((warn_unused_result));
BindScope checkWarningInt(int arg) __attribute__((warn_unused_result));
BindScope checkWarningFoo(int arg) __attribute__((warn_unused_result));
operator Foo*() { return m_ptr.get(); }
private:
std::unique_ptr<Foo> m_ptr;
};
template <typename... Args>
Test::BindScope Test::bind(Args&&... args) {
BindScope bindScope(*this);
return std::move(bindScope);
}
Test::BindScope Test::checkWarningFoo(int arg) {
BindScope bindScope(*this);
return std::move(bindScope);
}
Test::BindScope Test::checkWarningInt(int arg) {
return 0;
}
int main(int argc, char *argv[]) {
Test t;
t.bind(1, "foo"); // no warning <--- that's my bug
t.checkWarningFoo(1); // emits warning
t.checkWarningInt(1); // emits warning
}
t.C: In member function ‘Test::BindScope Test::checkWarningFoo(int)’:
t.C:38:19: warning: moving a local object in a return statement prevents copy
elision [-Wpessimizing-move]
38 | return std::move(bindScope);
| ~~~~~~~~~^~~~~~~~~~~
t.C:38:19: note: remove ‘std::move’ call
t.C: In function ‘int main(int, char**)’:
t.C:47:19: warning: ignoring return value of ‘Test::BindScope Test::bind(Args&&
...) [with Args = {int, const char (&)[4]}; Test::BindScope =
std::unique_ptr<Foo, FooDeleter>]’, declared with attribute warn_unused_result
[-Wunused-result]
47 | t.bind(1, "foo"); // no warning <--- that's my bug
| ^
t.C:31:17: note: declared here
31 | Test::BindScope Test::bind(Args&&... args) {
| ^~~~
t.C:48:23: warning: ignoring return value of ‘Test::BindScope
Test::checkWarningFoo(int)’, declared with attribute warn_unused_result
[-Wunused-result]
48 | t.checkWarningFoo(1); // emits warning
| ^
t.C:36:17: note: declared here
36 | Test::BindScope Test::checkWarningFoo(int arg) {
| ^~~~
t.C:49:23: warning: ignoring return value of ‘Test::BindScope
Test::checkWarningInt(int)’, declared with attribute warn_unused_result
[-Wunused-result]
49 | t.checkWarningInt(1); // emits warning
| ^
t.C:41:17: note: declared here
41 | Test::BindScope Test::checkWarningInt(int arg) {
| ^~~~
t.C: In instantiation of ‘Test::BindScope Test::bind(Args&& ...) [with Args =
{int, const char (&)[4]}; Test::BindScope = std::unique_ptr<Foo, FooDeleter>]’:
t.C:47:18: required from here
t.C:33:29: warning: moving a local object in a return statement prevents copy
elision [-Wpessimizing-move]
33 | return std::move(bindScope);
| ^
t.C:33:29: note: remove ‘std::move’ call
