This patch adjust the passing of parameters for the move_only_function,
copyable_function and function_ref. For types that are declared as being passed
by value in signature template argument, they are passed by value to the invoker,
when they are small (at most two pointers), trivially move constructible and
trivially destructible. The latter guarantees that passing them by value has not
user visible side effects.
In particular, this extends the set of types forwarded by value, that was
previously limited to scalars, to also include specializations of std::span and
std::string_view, and similar standard and program defined-types.
Checking the suitability of the parameter types requires the types to be complete.
As a consequence, the implementation imposes requirements on instantiation of
move_only_function and copyable_function. To avoid producing the errors from
the implementation details, a static assertion was added to partial
specializations of copyable_function, move_only_function and function_ref.
The static assertion uses existing __is_complete_or_unbounded, as arrays type
parameters are automatically decayed in function type.
Standard already specifies in [res.on.functions] p2.5 that instantiating these
partial specialization with incomplete types leads to undefined behavior.
libstdc++-v3/ChangeLog:
* include/bits/funcwrap.h (__polyfunc::__pass_by_rref): Define.
(__polyfunc::__param_t): Update to use __pass_by_rref.
* include/bits/cpyfunc_impl.h:: Assert that are parameters type
are complete.
* include/bits/funcref_impl.h: Likewise.
* include/bits/mofunc_impl.h: Likewise.
* testsuite/20_util/copyable_function/call.cc: New test.
* testsuite/20_util/function_ref/call.cc: New test.
* testsuite/20_util/move_only_function/call.cc: New test.
* testsuite/20_util/copyable_function/conv.cc: New test.
* testsuite/20_util/function_ref/conv.cc: New test.
* testsuite/20_util/move_only_function/conv.cc: New test.
* testsuite/20_util/copyable_function/incomplete_neg.cc: New test.
* testsuite/20_util/function_ref/incomplete_neg.cc: New test.
* testsuite/20_util/move_only_function/incomplete_neg.cc: New test.
Reviewed-by: Patrick Palka <ppalka@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
This patch implements C++26 copyable_function as specified in P2548R6.
It also implements LWG 4255 that adjust move_only_function so constructing
from empty copyable_function, produces empty functor. This falls from
existing checks, after specializing __is_polymorphic_function_v for
copyable_function specializations.
For compatible invoker signatures, the move_only_function may be constructed
from copyable_funciton without double indirection. To achieve that we derive
_Cpy_base from _Mo_base, and specialize __is_polymorphic_function_v for
copyable_function. Similary copyable_functions with compatible signatures
can be converted without double indirection.
As we starting to use _Op::_Copy operation from the _M_manage function,
invocations of that functions may now throw exceptions, so noexcept needs
to be removed from the signature of stored _M_manage pointers. This also
affects operations in _Mo_base, however we already wrap _M_manage invocations
in noexcept member functions (_M_move, _M_destroy, swap).
PR libstdc++/119125
libstdc++-v3/ChangeLog:
* doc/doxygen/stdheader.cc: Addded cpyfunc_impl.h header.
* include/Makefile.am: Add bits cpyfunc_impl.h.
* include/Makefile.in: Add bits cpyfunc_impl.h.
* include/bits/cpyfunc_impl.h: New file.
* include/bits/mofunc_impl.h: Mention LWG 4255.
* include/bits/move_only_function.h: Update header description
and change guard to also check __glibcxx_copyable_function.
(_Manager::_Func): Remove noexcept.
(std::__is_polymorphic_function_v<move_only_function<_Tp>>)
(__variant::_Never_valueless_alt<std::move_only_function<_Signature...>>)
(move_only_function) [__glibcxx_move_only_function]: Adjust guard.
(std::__is_polymorphic_function_v<copyable_function<_Tp>>)
(__variant::_Never_valueless_alt<std::copyable_function<_Signature...>>)
(__polyfunc::_Cpy_base, std::copyable_function)
[__glibcxx_copyable_function]: Define.
* include/bits/version.def: Define copyable_function.
* include/bits/version.h: Regenerate.
* include/std/functional: Define __cpp_lib_copyable_function.
* src/c++23/std.cc.in (copyable_function)
[__cpp_lib_copyable_function]: Export.
* testsuite/20_util/copyable_function/call.cc: New test based on
move_only_function tests.
* testsuite/20_util/copyable_function/cons.cc: New test based on
move_only_function tests.
* testsuite/20_util/copyable_function/conv.cc: New test based on
move_only_function tests.
* testsuite/20_util/copyable_function/copy.cc: New test.
* testsuite/20_util/copyable_function/move.cc: New test based on
move_only_function tests.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
Tomasz Kamiński