How to debug a multi-threaded program?

nalsrayatko · 11-29-2007, 02:10 AM

Hi all;

I am developing a multi thread program in Eclipse and I have some troubles with debugging. I have written several test programs for debugging, but it is very hard to read the output of the programs. There are too many threads and all of them write their messages to the same console screen, I can't understand which messages are belong to which thread.

Is there anyway to print the output of the different threads/processes to the different console screen?

For example, my program has 4 threads and they print out a message to the stdout. Is there a way to print out threads' messages to the different console screen? (by using pipes, execlp but without using tcp/ip )

Thanks for your helps
Yatko

JudyL · 11-29-2007, 08:39 AM

Quote:

Originally Posted by nalsrayatko

Hi all;

Is there anyway to print the output of the different threads/processes to the different console screen?

I can't address that, but I usually preface my thread tracing messages with the thread ID, thereby uniquely identifying which thread created the message.

Judy

i_grok · 11-29-2007, 09:13 AM

You can also write each thread's output to a separate file (e.g. threadFile1, threadFile2 ...).

Then open a console window for each thread and run:

Code:

tail -f threadFileX

It's not the fastest option, but it can help.

nalsrayatko · 11-29-2007, 01:18 PM

Thanks, I will use "tail" command, untill to find a better and faster way.

indienick · 11-29-2007, 01:57 PM

One thing I always do with non-quick-script programs I write (even with some), I add in my own debugging, showing the steps and a concise (not necessarily detailed) message telling me what it was trying to do when it failed, or why it failed (in the case I have something like a try-catch block).

Here's an example of what I mean (in pseudocode):

Code:

string program = "foo"

function write-to-stream(stream, message):
   string func = "write-to-stream"
   try:
      print $stream, $message
   catch (ioexception ioex):
      print [STDOUT|STDERR] "$program:$func:Failed to write $message to $stream"

write-to-stream(STDOUT, "hello, world")

Of course, it would be too time-consuming for you too go back and add something like this in now, but this is more or less just a guideline I follow as when I learned to program, it was without mechanisms like try-catch blocks (think QBASIC/QuickBASIC and C) and an method I implemented when I watched my classmates struggle to find the crippling bug in their code.