Subject: Re: Exception handling
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Date: Thu, 6 Jun 2002 15:22:40 -0400
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From: "Alex" <alex AT compuweigh DOT com>
To: <djgpp AT delorie DOT com>
Cc: <eliz AT is DOT elta DOT co DOT il>
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"Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il> wrote in message
news:<Pine DOT SUN DOT 3 DOT 91 DOT 1020606082218 DOT 15110H AT is>...
> 
> On Thu, 6 Jun 2002, Alex Oleynikov wrote:
> 
> > 1.First of all, I am using 'REDIR -e crash.dmp myprog.exe' to
capture the
> > stderr output from my application. In 99% of crash situations the
resulting
> > crash.dmp file is empty, although if I run the program directly I
can see
> > the stack traceback output on the screen. Also, if I redirect it to
a
> > printer it prints the whole thing fine. Why doesn't REDIR save this
> > information to my file?
> 
> It does for me.  I think this is something specific to your system or 
> your crashes.  What OS is that?  Can you post a short program that 
> crashes, for which `redir' doesn't produce a traceback in a file?

I am using PTS-DOS. I will try to write a small program to re-create
this behavior.

> Btw, if it's NT or Windows 2000, there's an incompatible program
called 
> redir.exe, so perhaps you inadvertently use that instead of the DJGPP 
> version of `redir'.

Unlikely, since I use DJGPP in plain DOS only.

> 
> > 2.I hooked my handlers to several signals (SIGINT, SIGABRT, SIGSEGV
and
> > SIGFPE). The handler basically saves a timestamp and the signal
description
> > to a file, displays a message on the screen and calls
> > __djgpp_traceback_exit( ) procedure. For some reason, when SIGABRT
signal is
> > being processed, the computer locks up completely when calling
> > __djgpp_traceback_exit(). I also tried using exit() or simply return
from
> > the signal handler (since the SIGABRT is raised from assert()) - the
result
> > is always the same - the computer locks up. Why is that?
> 
> SIGABRT is not a real exception, so it's treated a bit differently.  
> However, it shouldn't lock up.  Please show the code of your signal 
> handler, and how you install it, there's probably something wrong with

> that.

This was my mistake. While the message was displayed on the screen, some
activity was still going on the background in the application. As soon
as I made this message blocking the lock up is gone.

> > 2.If I will not be able to solve the problem with REDIR, is there a
way to
> > get an output similar to the one produced by
__djgpp_traceback_exit(), but
> > without terminating the application? In other words, can I somehow
save the
> > stack traceback to a log file from within my signal handler?
> 
> The sources of the library are freely available: download djlsr203.zip

> and look at the file src/libc/go32/dpmiexcp.c, where you will find the

> code that prints the traceback.

Thanks for pointing me to a right direction.
Thanks for you help.

Alex