Mail Archives: cygwin/2013/01/11/03:42:08
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I had previously reported "select() hanging after terminal killed"
(http://cygwin.com/ml/cygwin/2011-05/msg00418.html).
It turns out that select() does not get interrupted by a SIGWINCH signal
either (with likely the same cause).
This raises problems with interactive programs that want to react to
window size changes (like text editors).
See attached updated test case; run the program, while select() is
waiting (before 5 second timeout each), change window size and see no
interrupt.
On other systems, select() is interrupted (test case: from mintty,
remote login to SunOS; also showing the terminal is not involved in the
problem).
This bug did not exist in cygwin 1.5; I see some Changelog entries from
2011-12-13 or 2012-01-22 which might be related.
------
Thomas
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filename="select-intr.c"
#include <stdio.h>
#include <stdlib.h>
#include <sys/select.h>
#include <errno.h>
#include <signal.h>
int
peek (int fd, int msec)
{
fd_set readfds;
fd_set exceptfds;
struct timeval timeoutstru;
int nfds;
FD_ZERO (& readfds);
FD_SET (fd, & readfds);
FD_ZERO (& exceptfds);
FD_SET (fd, & exceptfds);
timeoutstru.tv_sec = msec / 1000;
timeoutstru.tv_usec = (msec % 1000) * 1000;
errno = 0;
printf ("calling select\n");
nfds = select (fd + 1, & readfds, 0, & exceptfds, & timeoutstru);
printf ("select -> %d (%s), read %02X except %02X\n",
nfds, strerror (errno), readfds, exceptfds);
return nfds;
}
void
catch_HUP (int hup)
{
printf ("HUP\n");
signal (SIGHUP, catch_HUP);
}
void
catch_WINCH (int hup)
{
printf ("WINCH\n");
signal (SIGWINCH, catch_WINCH);
}
int
main ()
{
int fdstdin = 0;
system ("stty -icanon");
signal (SIGHUP, catch_HUP);
signal (SIGWINCH, catch_WINCH);
while (1) {
char buf;
int buflen = 1;
int nfds = peek (fdstdin, 5000);
if (nfds > 0) {
int n;
printf ("calling read\n");
errno = 0;
n = read (fdstdin, & buf, buflen);
if (n <= 0) {
printf ("read -> %d (%s); exit\n", n, strerror (errno));
exit (0);
}
printf ("read -> %d: %c\n", n, buf);
}
sleep (2);
}
}
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