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Message-ID: <Pine.BSM.4.64L.2406170426130.32337@herc.mirbsd.org> Date: Mon, 17 Jun 2024 04:29:35 +0000 (UTC) From: Thorsten Glaser <tg@...bsd.de> To: musl@...ts.openwall.com Subject: Re: Question about flexible array 樊鹏 dixit: >The reason is a difference between gcc and g++: > >Flexible array members are not officially part of C++. >Flexible array members were officially standardized in C99. >/usr/include/bits/signal.h:35:23: error: flexible array member 'mcontext_t::__extcontext' not at end of 'struct tbb::detail::r1::coroutine_type' No, that’s not the problem here (the compiler allows that). The problem is this, in oneTBB itself: struct coroutine_type { coroutine_type() : my_context(), my_stack(), my_stack_size() {} ucontext_t my_context; void* my_stack; std::size_t my_stack_size; }; There’s a double problem here. One is the ordering. Changing to… struct coroutine_type { coroutine_type() : my_context(), my_stack(), my_stack_size() {} void* my_stack; std::size_t my_stack_size; ucontext_t my_context; }; … would fix that, but I *bet* that the surrounding code allocates its struct coroutine_type by a fixed size and copies my_context by sizeof(ucontext_t), which necessarily does not include the FAM. I’m not sure if it is even permissible for ucontext_t to contain a FAM; perhaps instead you need to figure out the exact or a maximum size and change the declaration (and the ABI, most likely) to that? Otherwise, all that’s left is to forbid userspace the copying of ucontext_t, which probably won’t fly… bye, //mirabilos -- “ah that reminds me, thanks for the stellar entertainment that you and certain other people provide on the Debian mailing lists │ sole reason I subscribed to them (I'm not using Debian anywhere) is the entertainment factor │ Debian does not strike me as a place for good humour, much less German admin-style humour”
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