Debugging with no serial port

Ben Warren bwarren at
Fri Aug 11 05:27:58 EST 2006


How about something a bit simpler like running gdb within a 'script'
context, which will log your session to a file.  Get gdb to print the
variables to the screen (using 'print' or whatever), wrap your data with
easily searchable characters (eg. ***data1 data2 data3***), then filter
your data from the script file with sed/awk or perl scripts?

A bit brute force, but bound to work.


On Thu, 2006-08-10 at 10:14 -0700, Martin, Tim wrote:
> This may be more of a question for GDB folks...but I'll post it here
> because it relates to embedded systems as well.
> I'm trying to validate some signal processing software on an embedded
> Virtex4 PowerPC 405.  Basically, the validation consists of calling
> functions and looking at their outputs.  Over time, there are several
> thousand numbers to look at, so manually looking at each number at a
> break point would be very time consuming (to put it mildly).
> The normal way I would go about doing this is to print out the data
> (e.g. to a serial port) and post-process the data somewhere else.  But
> on this particular target, I don't have a serial port.  So I thought
> about using GDB's breakpoint command list feature.  When the software
> has data it wants to print out, it calls a function "log_stuff".  I
> then set a breakpoint and command list in the "log_stuff" function,
> which writes out the variables I'm interested in checking out to a
> file named outputfile.bin.  E.g. the following command file does this:
> break log_stuff
> commands
>    silent
>    if (variable_logging_enabled)
>       append value outputfile.bin stuff1_variable
>       append value outputfile.bin stuff2_variable
>    end
>    cont
> end
> The problem I have with this approach is that GDB doesn't finish
> writing out everything before it continues executing the program, so a
> backlog develops.  So my first question would be, is there some GDB
> "flush" like command I could run before the cont statement?
> Second question would be - is there an easier way to accomplish what
> I'm trying to do, which is basically emulate a serial port with GDB.
> Tim
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> Linuxppc-embedded at
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