Mail Archives: cygwin/2007/04/03/10:43:06
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On Tue, Apr 03, 2007 at 10:13:20AM -0400, Bob Rossi wrote:
> On Mon, Apr 02, 2007 at 08:37:53PM -0400, Christopher Faylor wrote:
> > On Mon, Apr 02, 2007 at 08:07:23PM -0400, Bob Rossi wrote:
> > >I'm not exactly sure what has changed since the last release to cause
> > >this issue. However, here it is.
> > >
> > >When ctrl-z is typed, CGDB receives a SIGTSTP on both linux and cygwin.
> > >When CGDB is at the select loop and this happens on linux select returns
> > >-1 and errno is set to EINTR. My code simple does a 'continue' when this
> > >happens and the select loop is reentered. All works well. On cygwin,
> > >select does not return with -1. (I didn't check the return value but I
> > >can, I just compare to -1 in an if statement). In fact, select also
> > >detects that input is ready on stdin. This causes CGDB to get to a read
> > >system call (which is non blocking) and the read system call fails with
> > >errno set to EAGAIN. This causes CGDB to exit.
> > >
> > >The main loop looks something like this,
> > > if (select (max + 1, &rset, NULL, NULL, NULL) == -1)
> > > {
> > > if (errno == EINTR)
> > > continue;
> > > ..
> > > }
> > >
> > > if (FD_ISSET (STDIN_FILENO, &rset)) {
> > > handle_stdin
> > > }
> > >
> > >So, my question is, is there a bug with select on cygwin? Is select
> > >working properly and I should handle the read call differently? Why does
> > >it act differently than linux?
> >
> > You say that something changed between different releases but you don't
> > mention what those releases are. Is this releases of Cygwin? If so,
> > what releases?
> >
> > If this is as easy to demonstrate as you say, then a simple test case
> > is definitely called for.
>
> Hi Christopher,
>
> Attached is the test case. If I run it under linux, and then type ctrl-z, I
> never get into the user_input_loop call. If I run it in cygwin, I do.
>
> Hopefully I'm doing something wrong here. Please advise!
Ouch. Attached.
Bob Rossi
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#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/select.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <termios.h>
static struct termios term_attributes;
int
tty_cbreak (int fd, struct termios *orig)
{
struct termios buf;
if (tcgetattr (fd, &buf) < 0)
return -1;
/* Save the original state, for resetting later */
*orig = buf;
buf.c_lflag &= ~(ECHO | ICANON);
buf.c_iflag &= ~(ICRNL | INLCR);
buf.c_cc[VMIN] = 1;
buf.c_cc[VTIME] = 0;
#if defined (VLNEXT) && defined (_POSIX_VDISABLE)
buf.c_cc[VLNEXT] = _POSIX_VDISABLE;
#endif
#if defined (VDSUSP) && defined (_POSIX_VDISABLE)
buf.c_cc[VDSUSP] = _POSIX_VDISABLE;
#endif
if (tcsetattr (fd, TCSAFLUSH, &buf) < 0)
return -1;
return 0;
}
int
tty_set_attributes (int fd, struct termios *buf)
{
if (tcsetattr (fd, TCSAFLUSH, buf) < 0)
return -1;
return 0;
}
int
user_input_loop ()
{
fprintf (stderr, "HERE\r\n");
return 0;
}
static int
main_loop (void)
{
fd_set rset;
int max = STDIN_FILENO;
for (;;)
{
/* Reset the fd_set, and watch for input from GDB or stdin */
FD_ZERO (&rset);
FD_SET (STDIN_FILENO, &rset);
/* Wait for input */
if (select (max + 1, &rset, NULL, NULL, NULL) == -1)
{
if (errno == EINTR)
continue;
else
{
fprintf (stderr, __FILE__, __LINE__,
"select failed: %s", strerror (errno));
return -1;
}
}
/* Input received: Handle it */
if (FD_ISSET (STDIN_FILENO, &rset)) {
if (user_input_loop () == -1)
return -1;
}
}
return 0;
}
int
main (int argc, char *argv[])
{
if (tty_cbreak (STDIN_FILENO, &term_attributes) == -1)
{
fprintf (stderr, __FILE__, __LINE__, "tty_cbreak error");
exit (-1);
}
/* Enter main loop */
main_loop ();
if (tty_set_attributes (STDIN_FILENO, &term_attributes) == -1)
fprintf (stderr, __FILE__, __LINE__, "tty_reset error");
return 0;
}
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