[Perl/perl5] 8a548d: win32: initialise winsock unconditionally

  Branch: refs/heads/blead
  Home:   https://github.com/Perl/perl5
  Commit: 8a548d15292f2166cb07a69fc5fc943391b7fba5
      https://github.com/Perl/perl5/commit/8a548d15292f2166cb07a69fc5fc943391b7fba5
  Author: Tomasz Konojacki <me@xenu.pl>
  Date:   2023-03-17 (Fri, 17 Mar 2023)

  Changed paths:
    M win32/win32.c
    M win32/win32.h
    M win32/win32sck.c

  Log Message:
  -----------
  win32: initialise winsock unconditionally

The next commit needs it. Also, I don't think this optimisation is worth
the trouble.


  Commit: 8552f09f5cfe61a536a65f11290ef026f7aa0356
      https://github.com/Perl/perl5/commit/8552f09f5cfe61a536a65f11290ef026f7aa0356
  Author: Tomasz Konojacki <me@xenu.pl>
  Date:   2023-03-17 (Fri, 17 Mar 2023)

  Changed paths:
    M pod/perldelta.pod
    M win32/win32.c
    M win32/win32.h
    M win32/win32sck.c

  Log Message:
  -----------
  win32: inject a socket-aware version of CloseHandle() into the CRT

_close() on an fd calls CloseHandle(), which is illegal if the fd
contains a socket handle.

We previously worked around this by having our own close(), which called
closesocket() before calling _close()
(e601c439adce167078ac7b49550c0418ace86f94).

Amusingly, the author of that solution thought it's just a temporary
workaround:

  /*
   * close RTL fd while respecting sockets
   * added as temporary measure until PerlIO has real
   * Win32 native layer
   *   -- BKS, 11-11-2000
   */

To make it thread-safe, we had to manipulate the internals of file
descriptors, which kept changing
(b47a847f6284f6f98ad7509cf77a4aeb802d8fce).

Unfortunately, the C runtime has been rewritten and it no longer exposes
them at all. We had to disable the thread-safety fix in Visual C++ 2015
builds (1f664ef5314fb6e438137c44c95cf5ecdbdb5e9b). It also wouldn't work
with MinGW configured to use UCRT.

This commit introduces a new solution: we inject a socket-aware version
of CloseHandle() into the C runtime library. Hopefully, this will be
less fragile.

This also fixes a few issues that the original solution didn't:

  - Closing a busy pipe doesn't cause a deadlock (fixes #19963)

  - _dup2 properly closes an overwritten socket (fixes #20920)


Compare: https://github.com/Perl/perl5/compare/c1cac033a542...8552f09f5cfe

• [Perl/perl5] 8a548d: win32: initialise winsock unconditionally by xenu via perl5-changes