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| author | Jonathan Wakely <jwakely@redhat.com> | 2021-08-26 14:01:36 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2021-08-27 00:12:54 +0100 |
| commit | d38d26be33aba5d4c12429478375a47c474124d2 (patch) | |
| tree | c771210d2741aae1783e86489d3211d55bfa592a /gcc | |
| parent | 8cf428bfd3ca967b3d135e311d3e391998a39335 (diff) | |
| download | gcc-d38d26be33aba5d4c12429478375a47c474124d2.zip gcc-d38d26be33aba5d4c12429478375a47c474124d2.tar.gz gcc-d38d26be33aba5d4c12429478375a47c474124d2.tar.bz2 | |
libstdc++: Avoid a move in std::function construction (LWG 2447)
This makes the std::function constructor use perfect forwarding, to
avoid an unnecessary move-construction of the target. This means we need
to rewrite the _Function_base::_Base_manager::_M_init_functor function
to use a forwarding reference, and so can reuse it for the clone
operation.
Also simplify the SFINAE constraints on the constructor, by combining
the !is_same_v<remove_cvref_t<F>, function> constraint into the
_Callable trait.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
* include/bits/std_function.h (_function_base::_Base_manager):
Replace _M_init_functor with a function template using a
forwarding reference, and a pair of _M_create function
templates. Reuse _M_create for the clone operation.
(function::_Decay_t): New alias template.
(function::_Callable): Simplify by using _Decay.
(function::function(F)): Change parameter to forwarding
reference, as per LWG 2447. Add noexcept-specifier. Simplify
constraints.
(function::operator=(F&&)): Add noexcept-specifier.
* testsuite/20_util/function/cons/lwg2774.cc: New test.
* testsuite/20_util/function/cons/noexcept.cc: New test.
Diffstat (limited to 'gcc')
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