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3633cc5428
This feature is present in the C++23 draft. With Jakub's recent front-end changes we can implement constexpr equality by comparing the addresses of std::type_info objects. We do not need string comparisons, because for constant evaluation cases we know we aren't dealing with std::type_info objects defined in other translation units. The ARM EABI requires that the type_info::operator== function can be defined out-of-line (and suggests that should be the default), but to be a constexpr function it must be defined inline (at least for C++23 mode). To meet these conflicting requirements we make the inline version of operator== call a new __equal function when called at runtime. That is an alias for the non-inline definition of operator== defined in libsupc++. libstdc++-v3/ChangeLog: * config/abi/pre/gnu.ver (GLIBCXX_3.4.30): Export new symbol for ARM EABI. * include/bits/c++config (_GLIBCXX23_CONSTEXPR): Define. * include/std/version (__cpp_lib_constexpr_typeinfo): Define. * libsupc++/tinfo.cc: Add #error to ensure non-inline definition is emitted. (type_info::__equal): Define alias symbol. * libsupc++/typeinfo (type_info::before): Combine different implementations into one. (type_info::operator==): Likewise. Use address equality for constant evaluation. Call __equal for targets that require the definition to be non-inline. * testsuite/18_support/type_info/constexpr.cc: New test.
90 lines
2.5 KiB
C++
90 lines
2.5 KiB
C++
// Methods for type_info for -*- C++ -*- Run Time Type Identification.
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// Copyright (C) 1994-2022 Free Software Foundation, Inc.
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//
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// This file is part of GCC.
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//
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// GCC is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// GCC is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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#include <bits/c++config.h>
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#include <cstddef>
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#include "tinfo.h"
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std::type_info::
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~type_info ()
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{ }
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#if !__GXX_TYPEINFO_EQUALITY_INLINE
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#if __cplusplus > 202002L
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# error "this file must be compiled with C++20 or older to define operator=="
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#endif
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// We can't rely on common symbols being shared between shared objects.
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bool std::type_info::
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operator== (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
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{
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#if __GXX_MERGED_TYPEINFO_NAMES
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return name () == arg.name ();
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#else
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/* The name() method will strip any leading '*' prefix. Therefore
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take care to look at __name rather than name() when looking for
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the "pointer" prefix. */
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return (&arg == this)
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|| (__name[0] != '*' && (__builtin_strcmp (name (), arg.name ()) == 0));
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#endif
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}
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bool
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std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
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__attribute__((alias("_ZNKSt9type_infoeqERKS_")));
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#endif
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namespace std {
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// return true if this is a type_info for a pointer type
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bool type_info::
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__is_pointer_p () const
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{
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return false;
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}
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// return true if this is a type_info for a function type
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bool type_info::
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__is_function_p () const
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{
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return false;
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}
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// try and catch a thrown object.
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bool type_info::
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__do_catch (const type_info *thr_type, void **, unsigned) const
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{
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return *this == *thr_type;
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}
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// upcast from this type to the target. __class_type_info will override
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bool type_info::
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__do_upcast (const abi::__class_type_info *, void **) const
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{
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return false;
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}
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}
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