Re: gdb pty problem [Was: emacs gud-interface is not updated after gdb command execution (maybe because of incomplete output from gdb)]

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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Hi Takashi,


can you please have a look?


Thanks,
Corinna


On Jun  1 08:51, Ken Brown wrote:
> On 5/31/2016 5:41 AM, Corinna Vinschen wrote:
> > Any chance you could bisect Cygwin to help finding the culprit?
> 
> The culprit is
> 
> commit 252a07b0ad3353abcd0fcd9b1b65ff977acd679e
> Author: Takashi Yano <takashi.yano@nifty.ne.jp>
> Date:   Fri Apr 3 13:07:35 2015 +0900
> 
>    Cygwin hangs up if several keys are typed during outputting a lot of texts.
> 
>        * fhandler_tty.cc (fhandler_pty_slave::read): Change calculation of
>        "readlen" not to use "bytes_in_pipe" value directly.
> 
> 
> Reverting that commit fixes the problem.  To test, compile and run the attached file.
> 
> $ gcc gdbstc.cc
> 
> $ ./a
> 1-inferior-tty-set /dev/pty3
> 2-gdb-set height 0
> 3-gdb-set non-stop 1
> 4-file-list-exec-source-files
> 5-file-list-exec-source-file
> 6-gdb-show prompt
> 7-stack-info-frame
> 8-thread-info
> 9-break-list
> q
> *** using gdb
> =thread-group-added,id="i1"
> ~"GNU gdb (GDB) (Cygwin 7.10.1-1) 7.10.1\n"
> ~"Copyright (C) 2015 Free Software Foundation, Inc.\n"
> ~"License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>\nThis is free software: you are free to change and redistribute it.\nThere is NO WARRANTY, to the extent permitted by law.  Type \"show copying\"\nand \"show warranty\" for details.\n"
> ~"This GDB was configured as \"i686-pc-cygwin\".\nType \"show configuration\" for configuration details."
> ~"\nFor bug reporting instructions, please see:\n"
> ~"<http://www.gnu.org/software/gdb/bugs/>.\n"
> ~"Find the GDB manual and other documentation resources online at:\n<http://www.gnu.org/software/gdb/documentation/>.\n"
> ~"For help, type \"help\".\n"
> ~"Type \"apropos word\" to search for commands related to \"word\".\n"
> =cmd-param-changed,param="auto-load safe-path",value="/"
> (gdb)
> ...
> 
> In bad cases (bug present), the program hangs and doesn't complete until the gdb process is killed from a different terminal.  In good cases it runs to completion.
> 
> Ken

> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <pty.h>
> #include <string.h>
> #include <sys/wait.h>
> 
> void get_output (int fd);
> 
> int
> main (int argc, const char **argv) 
> {
>   int master;
>   pid_t pid;
> 
>   if ((pid = forkpty (&master, NULL, NULL, NULL)) < 0)
>     {
>       perror ("forkpty");
>       exit (1);
>     }
>   /* child */
>   if (pid == 0) 
>     {
>       const char *av[100];
>       // putenv ("HOME=/tmp");
>       int i = 0;
> #ifdef STRACE_GDB
>       av[i++] = "strace";
>       av[i++] = "-o";
>       av[i++] = "/tmp/strace.out";
> #ifdef __CYGWIN__
>       av[i++] = "--mask=all+paranoid";
> #endif
> #endif
>       av[i++] = argv[1] ?: "gdb";
>       fprintf (stderr, "*** using %s\n", av[0]);
>       av[i++] = "-i=mi";
>       av[i] = NULL;
>       execvp (av[0], (char * const *) av);
>       /* shouldn't get here */
>       exit (1);
>     }
>   /* parent */
>   const char *input[20];
> 
>   int i = 0;
>   input[i++] = "1-inferior-tty-set /dev/pty3\n";
>   input[i++] = "2-gdb-set height 0\n";
>   input[i++] = "3-gdb-set non-stop 1\n";
>   input[i++] = "4-file-list-exec-source-files\n";
>   input[i++] = "5-file-list-exec-source-file\n";
>   input[i++] = "6-gdb-show prompt\n";
>   input[i++] = "7-stack-info-frame\n";
>   input[i++] = "8-thread-info\n";
>   input[i++] = "9-break-list\n";
>   input[i++] = "q\n";
>   input[i] = NULL;
> 
>   for (int i = 0; input[i]; ++i)
>     {
>       write (master, input[i], strlen (input[i]));
>       // sleep (1);
>     }
>   get_output (master);
>   wait (NULL);
> }
> 
> void
> get_output (int fd)
> {
>   char buf[4096];
> 
>   while (1)
>     {
>       int nread = read (fd, buf, sizeof (buf));
>       if (nread > 0)
> 	write (STDOUT_FILENO, buf, nread);
>       else
> 	{
> 	  printf ("No more output.  nread %d\n", nread);
> 	  break;
> 	}
>     }
> }
> 
> 

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-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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