[Ovmsdev] Debugging

Geir Øyvind Vælidalo geir at validalo.net
Thu Nov 23 06:22:09 HKT 2017

Nice! This is just what I needed. Thanks Mike and Steve! 🙂


> 22. nov. 2017 kl. 23:20 skrev Michael Balzer <dexter at expeedo.de>:
> Also google "gdb cheat sheet" for some helpful command overview PDFs.
> If you cannot use "make monitor" or had the module disconnected from USB when the crash occurred, you can attach gdb to the crashed module like this:
> xtensa-esp32-elf-gdb -ex "set serial baud 115200" -ex "target remote /dev/ttyUSB0" -ex interrupt build/ovms3.elf 
> (replace the device by your USB serial device, path is relative to Open-Vehicle-Monitoring-System-3/vehicle/OVMS.V3)
> Regards,
> Michael
> Am 22.11.2017 um 23:10 schrieb Geir Øyvind Vælidalo:
>> Thanks a lot, Steve! Great explanation :-) 
>> I’m using Mac, so please send the binary and library. 
>> Best regards,
>> Geir
>>> 22. nov. 2017 kl. 23:03 skrev Stephen Casner <casner at acm.org <mailto:casner at acm.org>>:
>>> On Wed, 22 Nov 2017, Geir ?yvind V?lidalo wrote:
>>>> I see some of your are talking about gdb-stub, but I have never used
>>>> gbd and need some help.
>>>> How do I debug? What options do I have?
>>> Happy to help with that.  To use the gdb-stub you change the parameter
>>> in menuconfig / Component Config / ESP32-specific / Panic handler
>>> behavior / Invoke GDBStub.
>>> When the crash occurs, you'll be presented with a "gdb>" command
>>> prompt.  You can find references for "gdb commands" online.  Here is
>>> one:  http://www.yolinux.com/TUTORIALS/GDB-Commands.html <http://www.yolinux.com/TUTORIALS/GDB-Commands.html>
>>> The first command I would expect you will want is "bt" which displays
>>> a stack backtrace telling in which function each call is made,
>>> including the source line number.  The frames on the stack are
>>> numbered; you can give the command "frame N" where N is a frame number
>>> to change to the context of that frame, since the lowest one might not
>>> be the place where things started to go wrong.
>>> When you're at the right frame, you can use the "print" command to
>>> look at the value of variables.  If variable foo is a pointer, you can
>>> say "print *foo" to display the contents of the object foo points to.
>>> In many cases this will be enough to figure out the problem.  I also
>>> use the "x" command to examine memory by address in various ways.
>>> You can also use the "list" command to see a few lines of source code
>>> around the point in the code referenced by that stack frame.  Usually
>>> I just look at my source in a separate window.
>>> When using gdb on a real computer you can set breakpoints before
>>> starting the program, but I have not learned whether that is possible
>>> to do with the ESP32.
>>> As I mentioned in one of the emails, if you are running on a Mac you
>>> should use the gdb binary that I made which references the newer
>>> libiconv library in order to avoid gdb getting stuck in an infinite
>>> loop.  If so, let me know and I'll send the binary and library to you.
>>> If you are running on a different platform, you should check to see
>>> what version of libiconv DLL (Windows) or shared library (Linux) is
>>> referenced.  On my Mac the new one is 9.0.0 vs. 7.0.0.  The old one is
>>> usable, but you have to be careful not to give any command that might
>>> result in gdb tryinging to display a variable value that has non-ASCII
>>> chars.
>>>                                                        -- Steve
>>> _______________________________________________
>>> OvmsDev mailing list
>>> OvmsDev at lists.teslaclub.hk <mailto:OvmsDev at lists.teslaclub.hk>
>>> http://lists.teslaclub.hk/mailman/listinfo/ovmsdev <http://lists.teslaclub.hk/mailman/listinfo/ovmsdev>
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> -- 
> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
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