win32: workaround for pipe writability in poll(2)

A CGI script was found to hang when a large amount of data was
posted:

   #!/bin/sh
   echo "Content-type: text/plain;"
   echo
   if [ "$REQUEST_METHOD" = "POST" ]; then
       dd of=my.dat bs=1 count=${CONTENT_LENGTH}
       echo -n "success."
   else
       echo -n "error!"
   fi

This appears to be due to problems determining whether a pipe is
writable on Windows.  The Git for Windows project has a workaround
in their copy of GNUlib's poll(2) implementation.  The details are
in the commit message:

   https://github.com/git-for-windows/git/commit/94f4d01932279c419844aa708bec31a26056bc6b

Apply the same workaround here.

Saves 220-272 bytes.

(GitHub issue #468)

1 files changed, 13 insertions, 0 deletions

diff --git a/win32/poll.c b/win32/poll.c
index b39732887..fb95adea7 100644
--- a/win32/poll.c
+++ b/win32/poll.c
@@ -170,14 +170,17 @@ windows_compute_revents (HANDLE h, int *p_sought)
   INPUT_RECORD *irbuffer;
   DWORD avail, nbuffer;
   BOOL bRet;
+#if 0
   IO_STATUS_BLOCK iosb;
   FILE_PIPE_LOCAL_INFORMATION fpli;
   static PNtQueryInformationFile NtQueryInformationFile;
   static BOOL once_only;
+#endif
 
   switch (GetFileType (h))
     {
     case FILE_TYPE_PIPE:
+#if 0
       if (!once_only)
         {
           NtQueryInformationFile = (PNtQueryInformationFile)
@@ -185,6 +188,7 @@ windows_compute_revents (HANDLE h, int *p_sought)
                             "NtQueryInformationFile");
           once_only = TRUE;
         }
+#endif
 
       happened = 0;
       if (PeekNamedPipe (h, NULL, 0, NULL, &avail, NULL) != 0)
@@ -197,6 +201,14 @@ windows_compute_revents (HANDLE h, int *p_sought)
 
       else
         {
+                /* The writability of a pipe can't be detected reliably on Windows.
+                 * Just say it's OK.
+                 *
+                 * Details:
+                 *
+                 *    https://github.com/git-for-windows/git/commit/94f4d01932279c419844aa708bec31a26056bc6b
+                 */
+#if 0
           /* It was the write-end of the pipe.  Check if it is writable.
              If NtQueryInformationFile fails, optimistically assume the pipe is
              writable.  This could happen on Windows 9x, where
@@ -214,6 +226,7 @@ windows_compute_revents (HANDLE h, int *p_sought)
               || fpli.WriteQuotaAvailable >= PIPE_BUF
               || (fpli.OutboundQuota < PIPE_BUF &&
                   fpli.WriteQuotaAvailable == fpli.OutboundQuota))
+#endif
             happened |= *p_sought & (POLLOUT | POLLWRNORM | POLLWRBAND);
         }
       return happened;