From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 56924385841A for ; Wed, 5 Jan 2022 15:30:54 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 56924385841A Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-312-mpd7cBTtMluPik6S509zXg-1; Wed, 05 Jan 2022 10:30:51 -0500 X-MC-Unique: mpd7cBTtMluPik6S509zXg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1D7AA101F7A1; Wed, 5 Jan 2022 15:30:50 +0000 (UTC) Received: from localhost (unknown [10.33.36.252]) by smtp.corp.redhat.com (Postfix) with ESMTP id BE4B179A22; Wed, 5 Jan 2022 15:30:49 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: Implement P1328 "Making std::type_info::operator== constexpr" Date: Wed, 5 Jan 2022 15:30:48 +0000 Message-Id: <20220105153048.1775975-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" X-Spam-Status: No, score=-13.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=unavailable autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 05 Jan 2022 15:30:56 -0000 Tested powerpc64le-linux, pushed to trunk. 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. --- libstdc++-v3/config/abi/pre/gnu.ver | 3 + libstdc++-v3/include/bits/c++config | 10 +- libstdc++-v3/include/std/version | 1 + libstdc++-v3/libsupc++/tinfo.cc | 7 ++ libstdc++-v3/libsupc++/typeinfo | 96 ++++++++++++------- .../18_support/type_info/constexpr.cc | 48 ++++++++++ 6 files changed, 131 insertions(+), 34 deletions(-) create mode 100644 libstdc++-v3/testsuite/18_support/type_info/constexpr.cc diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver index c2f09a9290a..afd242b32aa 100644 --- a/libstdc++-v3/config/abi/pre/gnu.ver +++ b/libstdc++-v3/config/abi/pre/gnu.ver @@ -2424,6 +2424,9 @@ GLIBCXX_3.4.30 { # std::__timepunct::_M_am_pm_format(const char**) _ZNKSt11__timepunctI[cw]E15_M_am_pm_formatEPPK[cw]; + # Only defined #if ! __GXX_TYPEINFO_EQUALITY_INLINE + _ZNKSt9type_info7__equalERKS_; + } GLIBCXX_3.4.29; # Symbols in the support library (libsupc++) have their own tag. diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config index 3609793c0e6..c64b61b3c90 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 58760e69be8..f421056964e 100644 --- a/libstdc++-v3/include/std/version +++ b/libstdc++-v3/include/std/version @@ -295,6 +295,7 @@ // c++2b #define __cpp_lib_adaptor_iterator_pair_constructor 202106L #define __cpp_lib_byteswap 202110L +#define __cpp_lib_constexpr_typeinfo 202106L #define __cpp_lib_invoke_r 202106L #define __cpp_lib_ios_noreplace 202200L #define __cpp_lib_is_scoped_enum 202011L diff --git a/libstdc++-v3/libsupc++/tinfo.cc b/libstdc++-v3/libsupc++/tinfo.cc index f38472020d2..ef13dd33064 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 @@ -47,6 +51,9 @@ operator== (const std::type_info& arg) const _GLIBCXX_NOEXCEPT #endif } +bool +std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT +__attribute__((alias("_ZNKSt9type_infoeqERKS_"))); #endif namespace std { diff --git a/libstdc++-v3/libsupc++/typeinfo b/libstdc++-v3/libsupc++/typeinfo index 91c30997403..3018a510fd5 100644 --- a/libstdc++-v3/libsupc++/typeinfo +++ b/libstdc++-v3/libsupc++/typeinfo @@ -38,6 +38,10 @@ #pragma GCC visibility push(default) +#if __cplusplus >= 202100L +# define __cpp_lib_constexpr_typeinfo 202106L +#endif + extern "C++" { namespace __cxxabiv1 @@ -99,40 +103,12 @@ namespace std const char* name() const _GLIBCXX_NOEXCEPT { return __name[0] == '*' ? __name + 1 : __name; } -#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 +152,65 @@ 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 + bool __equal(const type_info&) const _GLIBCXX_NOEXCEPT; +#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 (std::__is_constant_evaluated()) + return this == &__arg; + + if (__name == __arg.__name) + return true; + +#if !__GXX_TYPEINFO_EQUALITY_INLINE + // ABI requires comparisons to be non-inline. + return __equal(__arg); +#elif !__GXX_MERGED_TYPEINFO_NAMES + // Need to do string comparison. + return __name[0] != '*' && __builtin_strcmp (__name, __arg.name()) == 0; +#else + return false; +#endif + } +# endif + + /** * @brief Thrown during incorrect typecasting. * @ingroup exceptions diff --git a/libstdc++-v3/testsuite/18_support/type_info/constexpr.cc b/libstdc++-v3/testsuite/18_support/type_info/constexpr.cc new file mode 100644 index 00000000000..07f4fb651f4 --- /dev/null +++ b/libstdc++-v3/testsuite/18_support/type_info/constexpr.cc @@ -0,0 +1,48 @@ +// { dg-options "-std=gnu++23 -frtti" } +// { dg-do compile { target c++23 } } + +#include + +#ifndef __cpp_lib_constexpr_typeinfo +# error "Feature-test macro for constexpr typeinfo missing in " +#elif __cpp_lib_constexpr_typeinfo != 202106L +# error "Feature-test macro for constexpr typeinfo has wrong value in " +#endif + +struct X { }; + +constexpr bool +test01() +{ + if (typeid(int) == typeid(long)) + return false; + + if (typeid(int) != typeid(int)) + return false; + + struct X { virtual ~X() { } }; + + if (typeid(X) != typeid(X)) + return false; + + if (typeid(X) == typeid(::X)) + return false; + + if (typeid(X) == typeid(int)) + return false; + + const auto& ti_x = typeid(X); + if (ti_x != ti_x) + return false; + + if (ti_x != typeid(X)) + return false; + + struct Y { }; + if (ti_x == typeid(Y)) + return false; + + return true; +} + +static_assert( test01() ); -- 2.31.1