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This feature is present in the C++23 draft. The ARM EABI requires that the type_info::operator== function can be defined out-of-line (and suggests that should be the default). With this patch, we fail to conform to that in C++23 mode. I think we might want to move the logic from operator== into a separate std::type_info::__equal function, which can be non-inline even if the actual type_info::operator== function is constexpr (and so implicitly inline). That isn't done by this patch, but probably should be. libstdc++-v3/ChangeLog: * 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. * libsupc++/typeinfo (type_info::name()): Avoid branching. (type_info::before): Combine different implementations into one. (type_info::operator==): Likewise. --- libstdc++-v3/include/bits/c++config | 10 +++- libstdc++-v3/include/std/version | 1 + libstdc++-v3/libsupc++/tinfo.cc | 4 ++ libstdc++-v3/libsupc++/typeinfo | 90 ++++++++++++++++++----------- 4 files changed, 70 insertions(+), 35 deletions(-) diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config index 4b7fa659300..4ae635c8a56 100644 --- a/libstdc++-v3/include/bits/c++config +++ b/libstdc++-v3/include/bits/c++config @@ -175,13 +175,21 @@ #endif #ifndef _GLIBCXX20_CONSTEXPR -# if __cplusplus > 201703L +# if __cplusplus >= 202002L # define _GLIBCXX20_CONSTEXPR constexpr # else # define _GLIBCXX20_CONSTEXPR # endif #endif +#ifndef _GLIBCXX23_CONSTEXPR +# if __cplusplus >= 202100L +# define _GLIBCXX23_CONSTEXPR constexpr +# else +# define _GLIBCXX23_CONSTEXPR +# endif +#endif + #ifndef _GLIBCXX17_INLINE # if __cplusplus >= 201703L # define _GLIBCXX17_INLINE inline diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version index 0930de82efa..e8d696fa72f 100644 --- a/libstdc++-v3/include/std/version +++ b/libstdc++-v3/include/std/version @@ -290,6 +290,7 @@ #if __cplusplus > 202002L // c++2b #define __cpp_lib_adaptor_iterator_pair_constructor 202106L +#define __cpp_lib_constexpr_typeinfo 202106L #define __cpp_lib_invoke_r 202106L #define __cpp_lib_is_scoped_enum 202011L #if __cpp_lib_concepts diff --git a/libstdc++-v3/libsupc++/tinfo.cc b/libstdc++-v3/libsupc++/tinfo.cc index a620e23e91c..5356fbbedd3 100644 --- a/libstdc++-v3/libsupc++/tinfo.cc +++ b/libstdc++-v3/libsupc++/tinfo.cc @@ -32,6 +32,10 @@ std::type_info:: #if !__GXX_TYPEINFO_EQUALITY_INLINE +#if __cplusplus > 202002L +# error "this file must be compiled with C++20 or older to define operator==" +#endif + // We can't rely on common symbols being shared between shared objects. bool std::type_info:: operator== (const std::type_info& arg) const _GLIBCXX_NOEXCEPT diff --git a/libstdc++-v3/libsupc++/typeinfo b/libstdc++-v3/libsupc++/typeinfo index 975321f2017..06769e0c243 100644 --- a/libstdc++-v3/libsupc++/typeinfo +++ b/libstdc++-v3/libsupc++/typeinfo @@ -38,6 +38,10 @@ #pragma GCC visibility push(default) +#if __cplusplus >= 202101L +# define __cpp_lib_constexpr_typeinfo 202106L +#endif + extern "C++" { namespace __cxxabiv1 @@ -97,42 +101,14 @@ namespace std /** Returns an @e implementation-defined byte string; this is not * portable between compilers! */ const char* name() const _GLIBCXX_NOEXCEPT - { return __name[0] == '*' ? __name + 1 : __name; } + { return __name + int(__name[0] == '*'); } -#if !__GXX_TYPEINFO_EQUALITY_INLINE - // In old abi, or when weak symbols are not supported, there can - // be multiple instances of a type_info object for one - // type. Uniqueness must use the _name value, not object address. - bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT; - bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT; -#else - #if !__GXX_MERGED_TYPEINFO_NAMES - /** Returns true if @c *this precedes @c __arg in the implementation's + /** Returns true if `*this` precedes `__arg` in the implementation's * collation order. */ - // Even with the new abi, on systems that support dlopen - // we can run into cases where type_info names aren't merged, - // so we still need to do string comparison. - bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT - { return (__name[0] == '*' && __arg.__name[0] == '*') - ? __name < __arg.__name - : __builtin_strcmp (__name, __arg.__name) < 0; } + bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT; - bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT - { - return ((__name == __arg.__name) - || (__name[0] != '*' && - __builtin_strcmp (__name, __arg.__name) == 0)); - } - #else - // On some targets we can rely on type_info's NTBS being unique, - // and therefore address comparisons are sufficient. - bool before(const type_info& __arg) const _GLIBCXX_NOEXCEPT - { return __name < __arg.__name; } - - bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT - { return __name == __arg.__name; } - #endif -#endif + _GLIBCXX23_CONSTEXPR + bool operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT; #if __cpp_impl_three_way_comparison < 201907L bool operator!=(const type_info& __arg) const _GLIBCXX_NOEXCEPT @@ -176,11 +152,57 @@ namespace std explicit type_info(const char *__n): __name(__n) { } private: - /// Assigning type_info is not supported. + // type_info objects cannot be copied. +#if __cplusplus >= 201103L + type_info& operator=(const type_info&) = delete; + type_info(const type_info&) = delete; +#else type_info& operator=(const type_info&); type_info(const type_info&); +#endif }; +#if __GXX_TYPEINFO_EQUALITY_INLINE + inline bool + type_info::before(const type_info& __arg) const _GLIBCXX_NOEXCEPT + { +#if !__GXX_MERGED_TYPEINFO_NAMES + // Even with the new abi, on systems that support dlopen + // we can run into cases where type_info names aren't merged, + // so we still need to do string comparison. + if (__name[0] != '*' || __arg.__name[0] != '*') + return __builtin_strcmp (__name, __arg.__name) < 0; +#else + // On some targets we can rely on type_info's NTBS being unique, + // and therefore address comparisons are sufficient. +#endif + + // In old abi, or when weak symbols are not supported, there can + // be multiple instances of a type_info object for one + // type. Uniqueness must use the __name value, not object address. + return __name < __arg.__name; + } +#endif + +#if __GXX_TYPEINFO_EQUALITY_INLINE || __cplusplus > 202002L + _GLIBCXX23_CONSTEXPR inline bool + type_info::operator==(const type_info& __arg) const _GLIBCXX_NOEXCEPT + { + if (__name == __arg.__name) + return true; + +#if !__GXX_MERGED_TYPEINFO_NAMES +# if __has_builtin(__builtin_is_constant_evaluated) + if (!__builtin_is_constant_evaluated()) +# endif + return __name[0] != '*' && __builtin_strcmp (__name, __arg.name()) == 0; +#endif + + return false; + } +# endif + + /** * @brief Thrown during incorrect typecasting. * @ingroup exceptions -- 2.31.1