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)

1 files changed, 0 insertions, 74 deletions

diff --git a/win32/win32sck.c b/win32/win32sck.c
index f08b7bea29..4edd1407a4 100644
--- a/win32/win32sck.c
+++ b/win32/win32sck.c
@@ -632,80 +632,6 @@ win32_socket(int af, int type, int protocol)
     return s;
 }
 
-/*
- * close RTL fd while respecting sockets
- * added as temporary measure until PerlIO has real
- * Win32 native layer
- *   -- BKS, 11-11-2000
-*/
-
-int my_close(int fd)
-{
-    int osf;
-    osf = TO_SOCKET(fd);/* Get it now before it's gone! */
-    if (osf != -1) {
-        int err;
-        err = closesocket(osf);
-        if (err == 0) {
-#ifdef _set_osfhnd
-            assert(_osfhnd(fd) == osf); /* catch a bad ioinfo struct def */
-            /* don't close freed handle */
-            _set_osfhnd(fd, INVALID_HANDLE_VALUE);
-            return close(fd);
-#else
-            (void)close(fd);    /* handle already closed, ignore error */
-            return 0;
-#endif
-        }
-        else if (err == SOCKET_ERROR) {
-            int wsaerr = WSAGetLastError();
-            err = convert_wsa_error_to_errno(wsaerr);
-            if (err != ENOTSOCK) {
-                (void)close(fd);
-                errno = err;
-                SetLastError(wsaerr);
-                return EOF;
-            }
-        }
-    }
-    return close(fd);
-}
-
-#undef fclose
-int
-my_fclose (FILE *pf)
-{
-    int osf;
-    osf = TO_SOCKET(win32_fileno(pf));/* Get it now before it's gone! */
-    if (osf != -1) {
-        int err;
-        win32_fflush(pf);
-        err = closesocket(osf);
-        if (err == 0) {
-#ifdef _set_osfhnd
-            assert(_osfhnd(win32_fileno(pf)) == osf); /* catch a bad ioinfo struct def */
-            /* don't close freed handle */
-            _set_osfhnd(win32_fileno(pf), INVALID_HANDLE_VALUE);
-            return fclose(pf);
-#else
-            (void)fclose(pf);   /* handle already closed, ignore error */
-            return 0;
-#endif
-        }
-        else if (err == SOCKET_ERROR) {
-            int wsaerr = WSAGetLastError();
-            err = convert_wsa_error_to_errno(wsaerr);
-            if (err != ENOTSOCK) {
-                (void)fclose(pf);
-                errno = err;
-                SetLastError(wsaerr);
-                return EOF;
-            }
-        }
-    }
-    return fclose(pf);
-}
-
 struct hostent *
 win32_gethostbyaddr(const char *addr, int len, int type)
 {