From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1921) id 04FB8385AC34; Thu, 21 Jul 2022 07:54:59 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 04FB8385AC34 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Sebastian Huber To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-8589] libstdc++: Fix lifetime bugs for non-TLS eh_globals [PR105880] X-Act-Checkin: gcc X-Git-Author: Jonathan Wakely X-Git-Refname: refs/heads/releases/gcc-12 X-Git-Oldrev: 7f596e4314cbd496f90d16a91962141a418558af X-Git-Newrev: ade3197134cc9ed2b7e589a7b58c73110ae13f1c Message-Id: <20220721075459.04FB8385AC34@sourceware.org> Date: Thu, 21 Jul 2022 07:54:59 +0000 (GMT) X-BeenThere: libstdc++-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 21 Jul 2022 07:54:59 -0000 https://gcc.gnu.org/g:ade3197134cc9ed2b7e589a7b58c73110ae13f1c commit r12-8589-gade3197134cc9ed2b7e589a7b58c73110ae13f1c Author: Jonathan Wakely Date: Wed Jun 8 10:43:57 2022 +0100 libstdc++: Fix lifetime bugs for non-TLS eh_globals [PR105880] This ensures that the single-threaded fallback buffer eh_globals is not destroyed during program termination, using the same immortalization technique used for error category objects. Also ensure that init._M_init can still be read after init has been destroyed, by making it a static data member. libstdc++-v3/ChangeLog: PR libstdc++/105880 * libsupc++/eh_globals.cc (eh_globals): Ensure constant init and prevent destruction during termination. (__eh_globals_init::_M_init): Replace with static member _S_init. (__cxxabiv1::__cxa_get_globals_fast): Update. (__cxxabiv1::__cxa_get_globals): Likewise. (cherry picked from commit 1e65f2ed99024f23c56f7b6a961898bcaa882a92) Diff: --- libstdc++-v3/libsupc++/eh_globals.cc | 51 ++++++++++++++++++++++++++---------- 1 file changed, 37 insertions(+), 14 deletions(-) diff --git a/libstdc++-v3/libsupc++/eh_globals.cc b/libstdc++-v3/libsupc++/eh_globals.cc index 3a003b89edf..768425c0f40 100644 --- a/libstdc++-v3/libsupc++/eh_globals.cc +++ b/libstdc++-v3/libsupc++/eh_globals.cc @@ -64,8 +64,26 @@ __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW #else -// Single-threaded fallback buffer. -static __cxa_eh_globals eh_globals; +#if __has_cpp_attribute(clang::require_constant_initialization) +# define __constinit [[clang::require_constant_initialization]] +#endif + +namespace +{ + struct constant_init + { + union { + unsigned char unused; + __cxa_eh_globals obj; + }; + constexpr constant_init() : obj() { } + + ~constant_init() { /* do nothing, union member is not destroyed */ } + }; + + // Single-threaded fallback buffer. + __constinit constant_init eh_globals; +} #if __GTHREADS @@ -90,32 +108,37 @@ eh_globals_dtor(void* ptr) struct __eh_globals_init { __gthread_key_t _M_key; - bool _M_init; + static bool _S_init; - __eh_globals_init() : _M_init(false) - { + __eh_globals_init() + { if (__gthread_active_p()) - _M_init = __gthread_key_create(&_M_key, eh_globals_dtor) == 0; + _S_init = __gthread_key_create(&_M_key, eh_globals_dtor) == 0; } ~__eh_globals_init() { - if (_M_init) + if (_S_init) __gthread_key_delete(_M_key); - _M_init = false; + _S_init = false; } + + __eh_globals_init(const __eh_globals_init&) = delete; + __eh_globals_init& operator=(const __eh_globals_init&) = delete; }; +bool __eh_globals_init::_S_init = false; + static __eh_globals_init init; extern "C" __cxa_eh_globals* __cxxabiv1::__cxa_get_globals_fast() _GLIBCXX_NOTHROW { __cxa_eh_globals* g; - if (init._M_init) + if (init._S_init) g = static_cast<__cxa_eh_globals*>(__gthread_getspecific(init._M_key)); else - g = &eh_globals; + g = &eh_globals.obj; return g; } @@ -123,7 +146,7 @@ extern "C" __cxa_eh_globals* __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW { __cxa_eh_globals* g; - if (init._M_init) + if (init._S_init) { g = static_cast<__cxa_eh_globals*>(__gthread_getspecific(init._M_key)); if (!g) @@ -140,7 +163,7 @@ __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW } } else - g = &eh_globals; + g = &eh_globals.obj; return g; } @@ -148,11 +171,11 @@ __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW extern "C" __cxa_eh_globals* __cxxabiv1::__cxa_get_globals_fast() _GLIBCXX_NOTHROW -{ return &eh_globals; } +{ return &eh_globals.obj; } extern "C" __cxa_eh_globals* __cxxabiv1::__cxa_get_globals() _GLIBCXX_NOTHROW -{ return &eh_globals; } +{ return &eh_globals.obj; } #endif