9a0b518a82
This adds the overloads of std::make_shared and std::allocate_shared for creating arrays, added to C++20 by P0674R1. It also adds std::make_shared_for_overwrite, added to C++20 by P1020R1 (and renamed by P1973R1). The std::make_unique_for_overwite overloads are already supported. The original std::make_shared overload is changed to construct a shared_ptr directly instead of calling std::allocate_shared. This removes a function call at runtime, and avoids having to do overload resolution for std::allocate_shared, now that there are five overloads of it. Allocating a shared array is done by a new __shared_count constructor. An array is allocated with space for additional elements at the end and an instance of new _Sp_counted_array class template is constructed in that unused capacity. The non-array form of std::make_shared_for_overwrite uses the same __shared_count constructor as the original std::make_shared overload, but a new partial specialization of _Sp_counted_ptr_inplace is selected when the allocator's value_type is the new _Sp_overwrite_tag type. That new partial specialization default-initializes its contained object and destroys it with a destructor call rather than using the allocator. Despite being C++20 features, this implementation only uses concepts conditionally, with workarounds when they are not supported. This allows it to work with older non-GCC compilers (Clang 9 and icc 2021). At some point we can simplify the code by removing the workarounds. libstdc++-v3/ChangeLog: * include/bits/shared_ptr.h (__cpp_lib_shared_ptr_weak_type): Correct type of macro value. (shared_ptr): Add additional friend declarations. (make_shared, allocate_shared): Constrain existing overloads and remove static_assert. * include/bits/shared_ptr_base.h (__cpp_lib_smart_ptr_for_overwrite): New macro. (_Sp_counted_ptr_inplace<T, Alloc, Lp>): New partial specialization for use with make_shared_for_overwrite. (__cpp_lib_shared_ptr_arrays): Update value for C++20. (_Sp_counted_array_base): New class template. (_Sp_counted_array): New class template. (__shared_count(_Tp*&, const _Sp_counted_array_base&, _Init)): New constructor for allocating shared arrays. (__shared_ptr(const _Sp_counted_array_base&, _Init)): Likewise. * include/std/version (__cpp_lib_shared_ptr_weak_type): Correct type. (__cpp_lib_shared_ptr_arrays): Update value for C++20. (__cpp_lib_smart_ptr_for_overwrite): New macro. * testsuite/20_util/shared_ptr/creation/99006.cc: Adjust expected errors. * testsuite/20_util/shared_ptr/creation/array.cc: New test. * testsuite/20_util/shared_ptr/creation/overwrite.cc: New test. * testsuite/20_util/shared_ptr/creation/version.cc: New test. * testsuite/20_util/unique_ptr/creation/for_overwrite.cc: Check feature test macro. Test non-trivial default-initialization. |
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| libsupc++ | ||
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| python | ||
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| src | ||
| testsuite | ||
| ChangeLog | ||
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| ChangeLog-2021 | ||
| Makefile.am | ||
| Makefile.in | ||
| README | ||
| acinclude.m4 | ||
| aclocal.m4 | ||
| config.h.in | ||
| configure | ||
| configure.ac | ||
| configure.host | ||
| crossconfig.m4 | ||
| fragment.am | ||
| linkage.m4 | ||
README
file: libstdc++-v3/README New users may wish to point their web browsers to the file index.html in the 'doc/html' subdirectory. It contains brief building instructions and notes on how to configure the library in interesting ways.