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Date: Mon, 18 Aug 2008 13:55:20 +0200
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Subject: cygwin 1.7.0-28: Broken pipe signal broken?
From: "Christian Franke" <Christian DOT Franke AT t-online DOT de>
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During testing of my packages on 1.7, I got the following error message
from the grub-mkrescue script from package grub:

$ cat boot.img /dev/zero | dd bs=1024 count=1440 > floppy.img
cat: write error: No space left on device

But due to a hack in coreutils*/lib/full_write.c, the error message is
misleading.


The following test program demonstrates the root of the problem:

===== testpipe.c =====
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>

void sigpipe_handler()
{
  write(2, "[SIGPIPE!]", 10);
}

int main()
{
  static char buf[1024*1024];
  signal(SIGPIPE, sigpipe_handler);
  errno = 0;
  int n = write(1, buf, sizeof(buf));
  fprintf(stderr, "write = %d, errno = %d\n", n, errno);
  return 0;
}
======================


Result on 1.5.25-15:

$ ./testpipe | dd bs=1 count=1 >/dev/null 2>/dev/null
[SIGPIPE!]write = -1, errno = 32

Result on 1.7.0-28:

$ ./testpipe | dd bs=1 count=1 >/dev/null 2>/dev/null
write = 0, errno = 32


According to strace, errno=EPIPE is set in
fhandler_base::wait_overlapped() due to a failing GetOverlappedResult().

Missing raise(SIGPIPE) call in fhandler_base::write_overlapped() ?

Hope this helps,
    Christian

PS: No other issues found so far - nice work!




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