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From:	"Pierluigi 'Lanugo' Rolando" <lanugo AT ica-net DOT it>
To:	"Cygwin" <cygwin AT cygwin DOT com>
Subject:	Help with unix sockets and poll
Date:	Tue, 27 Aug 2002 10:35:35 +0200
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Hi,
I've tried to port some code that relies heavily on unix domain sockets for
IPC from Linux to Cygwin, and I've encountered some problems. It seems that
either unix domain sockets (created by socketpair() ) or the poll() library
call are broken.
I'm attaching the smallest test case I've been able to write that reproduces
the problem. Under linux (2.4.19/2.4.18 w/ glibc 2.2.4) the program
terminates correctly, while under cygwin it reports a POLLERR after the
first character is written on the socket. My cygwin DLL is version
1.3.12-cygwin-1-3-12-1, and gcc -v reports "Reading specs from
/usr/lib/gcc-lib/i686-pc-cygwin/2.95.3-5/specs | gcc version 2.95.3-5
(cygwin special)". I've done some researching on the net in order to find
out whethere I'm the first to experience this problem, and I haven't found
anything.

I've also downloaded and quickly checked the winsup sources, but I really
don't know Cygwin enough to be able to debug its sources (moreover, it could
be a flaw in my code).

Sorry for my bad english and thank you for you patience,
P. Rolando aka Lanugo of the Wandering Souls



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	filename="ubug.c"

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/poll.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>

int main(void)
{
	int ss[2];
	int i, j;
	struct pollfd pfd[2];
	char str[] = "w";

	if(socketpair(PF_UNIX, SOCK_STREAM, 0, ss) != 0) {
		fprintf(stderr, "socketpair: failed\n");
		return 1;
	}

	for(i = 0; i < 2; ++i)
		pfd[i].fd = ss[i];

	for(j = 0; j < 10; ++j) {
		for(i = 0; i < 2; ++i) {
			pfd[i].events = (POLLIN | POLLOUT);
		}

		poll(pfd, 2, -1);

		for(i = 0; i < 2; ++i)
			if(pfd[i].revents & POLLERR) {
				fprintf(stderr, "POLLERR: %d\n", pfd[i].fd);
				return 1;
			}

		if(pfd[0].revents & POLLOUT) {
			send(pfd[0].fd, (void *)str, 1, 0);
			fprintf(stderr, "w");
		}

		if(pfd[1].revents & POLLIN) {
			char buffer[1024];
			recv(pfd[1].fd, buffer, sizeof(buffer), 0);
			printf("W");
		}
	}

	return 0;
}


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