debugging with gdb - victronenergy/venus GitHub Wiki

Note: available since Venus OS v3.70

install required packages

First make sure opkg is setup correctly. There after install the compiler, libc-dbg and gdb.

opkg install libc-dbg packagegroup-core-buildessential gdb

simple test

create a test program, hello.c

#include <stdio.h>

int main() {
	int n;
	for (n = 0; n < 10; n++)
		printf("hello %d\n", n);
	return 0;
}

and compile it with gcc -g hello.c -o hello. Mind the -g for debugging.

start gdb

Note that after start the symbols for the shared libraries should also be loaded.

root@ekrano:~# gdb hello
GNU gdb (GDB) 14.2
Copyright (C) 2023 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "arm-ve-linux-gnueabi".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from hello...
(gdb) start
Temporary breakpoint 1 at 0x10434: file hello.c, line 5.
Starting program: /data/home/root/hello 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/libthread_db.so.1".

Temporary breakpoint 1, main () at hello.c:5
5		for (n = 0; n < 10; n++)
(gdb) info sharedlibrary 
From        To          Syms Read   Shared Object Library
0xb6fd8a00  0xb6ff789c  Yes         /lib/ld-linux-armhf.so.3
0xb6e88ec0  0xb6fa30c0  Yes         /lib/libc.so.6

Not going to repeat the gdb help here, just search the internet, but some useful commands are list / step / stepi / next / nexti / break / run / backtrace and info registers. e.g.:

(gdb) list
27	__printf (const char *format, ...)
28	{
29	  va_list arg;
30	  int done;
31	
32	  va_start (arg, format);
33	  done = __vfprintf_internal (stdout, format, arg, 0);
34	  va_end (arg);
35	
36	  return done;

tui mode

Instead of using list etc, tui mode can be entered with layout next or start gdb with -tui. One Key binding is important ctrl + x followed by o to move focus back to the control window.