Unix Technical Digest V2 #21

[Heiby]

Unix Technical Digest       Wed, 13 Dec 85       Volume  2 : Issue  21

Today's Topics:
                           dbx and signals
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Date: Wed, 6 Nov 85 16:51:48 mst
From: seismo!hao!woods (Greg Woods)
Subject: dbx and signals

   I need some help with using dbx on a VAX 11/750 under 4.2BSD. I am having
trouble getting it to work on programs that use signals. The documentation
on exactly what the "catch" and "ignore" commands do is sketchy to say
the least. 
  I have a program that does graphics, and it works by forking off the 
metacode translator, which is a process that translates the more-or-less
device-independent output of the higher-level graphics routines for the 
particular graphics device. It has an option that lets you type 'y' after
the frame is plotted on your screen and have that frame saved in a file. It
works using signals. A 14 is sent if you don't type 'y' and a 15 is sent
if you do. Obviously, the translator catches these signals appropriately.
It  calls pause after each frame and waits for the signal from the parent.
The problem is, when running my program under dbx, I cannot get it to
continue execution after the end of the frame, no matter how much I play
with the catch and ignore commands first. If I run the translator in
a mode which simply puts the metacode into a file instead of displaying
it on the screen (and hence, does not play around with signals) then it
works fine.
  Does anyone know how to use dbx on programs which fork off child processes
and play around with signals?

--Greg

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Ronald W. Heiby / netnews at wnuxb.UUCP
AT&T Information Systems, Inc., Lisle, IL  (CU-D21)