[MinGW-Notify] [mingw] #38607: Improved standards support for aligned memory allocators

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Sun Apr 19 22:03:02 JST 2020


#38607: Improved standards support for aligned memory allocators

  Open Date: 2018-09-17 19:25
Last Update: 2020-04-19 14:03

URL for this Ticket:
    https://osdn.net//projects/mingw/ticket/38607
RSS feed for this Ticket:
    https://osdn.net/ticket/ticket_rss.php?group_id=3917&tid=38607

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Last Changes/Comment on this Ticket:
2020-04-19 14:03 Updated by: keith

Comment:

I've simplified the previous implementation of both the ISO-C11 aligned_alloc
(), and the POSIX.1-2001 posix_memalign() functions, and separated them into
two individual patches; please note that the latter is dependent on the former,
to the extent that the former substitutes __mingw_free() and __mingw_realloc()
for free() and realloc() respectively.



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Ticket Status:

      Reporter: keith
         Owner: (None)
          Type: Feature Request
        Status: Open
      Priority: 5 - Medium
     MileStone: (None)
     Component: WSL
      Severity: 5 - Medium
    Resolution: None
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Ticket details:

Microsoft introduced _aligned_malloc(), and associated functions, with
MSVCR70.DLL. Although subsequently supported in MSVCRT.DLL, from WinXP onwards,
exposure of these APIs interferes with a clean build of GCC — not only insofar
as, having detected presence of the APIs, GCC would become dependent on WinXP
and later, thus needlessly breaking legacy support, but furthermore, the GCC
sources neglect to include the requisite <malloc.h> header file, and thus do
not build cleanly.

Legacy support for similar APIs was added to MinGW, in 2003/2004, under feature
request #260; however, it may be ill-advised to make GCC dependent on these
MinGW specific APIs, for the following reasons:­­—

 1. A patch, to incorporate them, would be unlikely to be accepted upstream.
 2. If the APIs are not detected, GCC will provide its own replacement
    functions.
 3. A review reveals potential flaws in the MinGW implementation.

Consequently, I suggest:—

 1. **Not** exposing the Microsoft APIs in libmsvcrt.a
 2. Reworking the MinGW implementation, to address potential flaws.
 3. Consider adding support for ISO-C11's aligned_alloc() and POSIX.1's
    posix_memalign() APIs.



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URL for this Ticket:
    https://osdn.net/projects/mingw/ticket/38607
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