Add #include <GDBStub.h> to the sketch
Upload the sketch
Redirect serial port to TCP port:
```
tcp_serial_redirect.py -p /dev/tty.SLAB_USBtoUART -b 115200 --spy -P 9980 --rts=0 --dtr=0
```
Change port and baud rate as necessary. This command requires python and pyserial.
Observe serial output:
```
nc localhost 9980
```

Once crash happens, close nc and start gdb:

xtensa-lx106-elf-gdb /path/to/Sketch.cpp.elf -ex "target remote :9980"

Or, using the provided gdbcmds file:

xtensa-lx106-elf-gdb /path/to/Sketch.cpp.elf -x gdbcmds

Tips and tricks

To halt the target when software WDT fires, add
```
((int*)0) = 0;
```
at the top of __wrap_system_restart_local in core_esp8266_postmortem.c.

License

Espressif MIT License. See License file.