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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. |
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| testsuite | ||
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| ChangeLog | ||
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| config.h.in | ||
| configure | ||
| configure.ac | ||
| configure.host | ||
| crossconfig.m4 | ||
| fragment.am | ||
| linkage.m4 | ||
| Makefile.am | ||
| Makefile.in | ||
| 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.