LANGUAGE » C

Debug

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Gdb

The binary must be compiled with -g.

If using a more complex Makefile, use CFLAGS = -g -O0 (See compile).

shell

gcc -g -o myapp main.c

Start gdb with the app and optionally a core dump file.

shell

gdb myapp
gdb myapp core

TIP

Check where core dumps are created in your system by seeing the contents of /proc/sys/kernel/core_pattern.

The command ulimit -c unlimited may also be useful.

The most commonly used commands are:

Command	Description
`b` `break`	Set breakpoint at specified location. Assign location as `script.c:10` `func_name` (see more here)
`r` `run`	Start execution.
`p` `print`	Print value of expression `EXPR`.
`n` `next` `nexti`	Execute next line (step-over).
`s` `step` `stepi`	Execute subroutine (step-into).
`fin` `finish`	Execute until selected stack frame returns (step-out).
`u` `until`	Execute until past the current line, useful for loops.
`c` `continue`	Continue program until it finishes or until next breakpoint.

Information extracted from the neomutt documentation.

Use two terminals, in the first one run:

shell

tty
sleep 1d

In the second one, start gdb and configure it with:

shell

# Inside gdb prompt
tty /dev/pts/5  # Device of the first terminal
handle SIGPIPE noprint nostop
set args -d 2   # Default parameters
run

Press Ctrl+C in the second terminal to insert more debug commands (breakpoint etc).