Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!mips!apple!uokmax!servalan!rmtodd
From: rmtodd@servalan.uucp (Richard Todd)
Newsgroups: comp.windows.x
Subject: Re: How do you use an Xterm with a debugger
Message-ID: <1991Mar15.074424.857@servalan.uucp>
Date: 15 Mar 91 07:44:24 GMT
References: <1991Mar13.011536.17184@motcad.portal.com> <1991Mar14.072808.20247@Think.COM>
Organization: Ministry of Silly Walks
Lines: 32

barmar@think.com (Barry Margolin) writes:

>In article <1991Mar13.011536.17184@motcad.portal.com> jtc@motcad.portal.com (J.T. Conklin) writes:
>>I would like to be able to open an Xterm so I can redirect terminal output
>>to it from within gdb.

>Why don't you just run gdb from the xterm window?

Uh, I think you've misinterpreted slightly what the original poster's
after.  You see, gdb has a command that allows the target program to do all
its I/O on a different tty (or pseudo-tty) than the one that gdb is running
on.  This is very useful if you're debugging curses applications, where
otherwise the gdb output would mess up your fancy display and make it hard
to figure out what's going on.  So what the guy wants is to run gdb in one
xterm window and have the target program's I/O go thru *another* xterm
window.  But, by default xterm puts a shell on its pseudo-tty, and when
both your target program and the shell try to read from the same tty, Bad
Things happen.  There are a couple of ways to work around this.  The cheap
and sleazy way (the one I used :-) was to simply type "sleep 10000" in the
target xterm window and let gdb attatch the target program to that tty.
Obviously, this will run into problems if your program expects to receive
signals from the keyboard (i.e. the default signal-causing behaviour of ^C
etc isn't disabled)--the ^C will kill the sleep and the shell will return
to try and grab your input.  (It also runs into problems if it takes more
than 10000 seconds==2.7 hours to debug your program...) The more elegant
solution is to write a special purpose program to just sit there, turn off
all keyboard signals, and do nothing.  It's a fairly straighforward 
exercise in C coding.  
--
Richard Todd	rmtodd@uokmax.ecn.uoknor.edu  rmtodd@chinet.chi.il.us
	rmtodd@servalan.uucp
"Try looking in the Yellow Pages under 'Psychotics'." -- Michael Santana