In mid-2018, David Gressett raised an issue, privately among the MinGW developers, (of whom he is one, and thus he has access to their private forum), relating to problems he was experiencing when building the Ada component of GCC; specifically, the build configuration expected to link with Microsoft's over-aligned heap allocator, but was unable to do so. Investigation revealed that the GCC configuration process was finding a reference to Microsoft's _aligned_malloc() in libmsvcrt.a, (it had been added to MSVCRT.DLL, from Vista onward, which would have broken support for legacy platforms, which MinGW still aims to accommodate); however, having identified availability of the API, the GCC Ada implementation was then found to be broken w.r.t. correct header inclusion, and even w.r.t. feature test macro definitions being placed too late to have any effect. Nonetheless, identification of the issue prompted a review, and ultimate rewrite, of the existing provisions within MinGW for support of over-aligned heap memory allocation. The outcome of that review may be found at https://osdn.net/projects/mingw/ticket/38607. It may be noted, from that ticket, that having corrected deficiencies of the original MinGW over-aligned heap allocator API, I went on to propose implementation of ISO-C11's aligned_alloc() function, (which contrary to Microsoft's assertion, in their C++ language conformance document: https://docs.microsoft.com/en-us/cpp/overview/visual-cpp-language-conformance?view=vs-2019 > C11: The Universal CRT implemented the parts of the C11 Standard > Library that are required by C++17, with the exception of C99 > strftime() E/O alternative conversion specifiers, C11 fopen() > exclusive mode, and C11 aligned_alloc(). The latter is unlikely to be > implemented, because C11 specified aligned_alloc() in a way that's > incompatible with the Microsoft implementation of free(): namely, > that free() must be able to handle highly aligned allocation. is actually quite trivial to implement), together with POSIX.1-2001's posix_memalign() function, (which is equally trivial to implement). At the time, I invited — on the ticket only — a peer review of the two additional functions, and left it at that; to date, no one has taken me up on that invitation. Recently, this came to my attention again, on account of its relevance to new ticket https://osdn.net/projects/mingw/ticket/40315. As I have noted on this new ticket, applying the <stdlib.h> patch to implement ISO-C11's aligned_alloc() will also DTRT w.r.t. the GCC implementation of C++17's std::aligned_alloc(). Consequently, I'd like to reiterate the invitation for peer review, and extend it to the wider MinGW user community; if no one offers a reasoned objection, by the end of April, I would like to include the proposed implementations of aligned_alloc(), and of posix_memalign(), in upcoming mingwrt-5.3.1. -- Regards, Keith. Public key available from keys.gnupg.net Key fingerprint: C19E C018 1547 DE50 E1D4 8F53 C0AD 36C6 347E 5A3F -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: OpenPGP digital signature URL: <https://lists.osdn.me/mailman/archives/mingw-users/attachments/20200420/9830bdfb/attachment.sig>
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