Usefull commands

Some usefull commands that should get you started with debugging your program

  • Just pressing enter – Repeat last command

  • help

  • help <command-or-category>

  • info locals – Inspect your locals
  • where – Shows the current stack trace

  • list or l – List lines where execution is at

  • continue or fg or c – Continue to run the program
  • step or s – Step program, will step into functions

  • next or n – Step programto next line, will step over functions

  • break, brea, bre, br or b – Set breakpoint, use as break <sourcefile>:<line-number>
  • delete, del, d – Delete all or some breakpoints
  • watch – Set a watchpoint for an expression, stops execution if the value of an expression changes

Set arbitrary breakpoint

$ gdb ./build/application/binary-to-debug
...

(gdb) break Main.cpp:31
Breakpoint 1 at 0x344e: file /home/user/repos/program/application/Main.cpp, line 31.
(gdb) run
Starting program: /home/user/repos/program/build/application/binary-to-debug

Breakpoint 1, main () at /home/user/repos/program/application/Main.cpp:31
31          std::cout << "add breakpoint here" << std::endl;
(gdb) where
#0  main () at /home/user/repos/program/application/Main.cpp:31

Breaking on any exception

You can use the catch throw command to break on any exception.

$ gdb ./build/application/binary-to-debug

...

(gdb) catch throw
Catchpoint 1 (throw)
(gdb) run
Starting program: /home/user/repos/program/build/application/binary-to-debug

Catchpoint 1 (exception thrown), 0x00007ffff7e0a87e in __cxa_throw ()
   from /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/libstdc++.so.6
(gdb) where
#0  0x00007ffff7e0a87e in __cxa_throw () from /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/libstdc++.so.6
#1  0x00005555555574d0 in main () at /home/user/repos/program/application/Main.cpp:35