web/content/notes/ready/gdb.md

title, description, draft, tags, author, showToc

title	description	draft	tags	author	showToc
Debugging [GDB]		false	programming	TrudeEH	true

GDB Debugging

Compile with Debug Information

To allow gdb access to the source code (Provides debug symbols - Do not share publicly as it contains the source code).

gcc -g <file>

Look for / Fix Bugs

First, initialize gdb with the executable to debug.

gdb ./<executable> --tui

After gdb is ready, we can use the following commands:

Command	Description
lay next	Switch to the next layout (Enables TUI mode if disabled - Allows for reading the code while debugging both in C and ASM).
ref	Refresh (if a program prints to the terminal, it can break gdb's interface).`
q	Quit gdb.
b main	Add a breakpoint at the main function.
b	Place a breakpoint at the current line.
b <N>	Place a breakpoint at line N.
b +<N>	Place a breakpoint N lines down.
b <fn>	Place a breakpoint at fn function.
d	Delete all breakpoints.
d <N>	Delete breakpoint number N.
clear <fn>	Clear the breakpoint set to fn function.
n	Execute up to the next line in C. If a function call is found, execute the function completely.
s	Execute up to the next line in C. (Jump over)
s <N>	Run N lines.
u	Same as n, but if in a loop, execute until the loop exits.
nexti	Execute up to the next instruction (line in ASM).
r	Run the program until a breakpoint or error is reached.
c	Continue running the program until a breakpoint or error is reached.
x/i $pc	Examine the previous instruction (View memory).
info registers	Read the CPU registers used by the program.
bt	See the call stack up to the current line. (How we got here, so to speak)
print sizeof(<variable>)	Check the size of a struct/variable/pointer.
p <var>	Print variable var value.
info break	List breakpoints.

Check for Memory Leaks

Use valgrind to check for lost memory.

valgrind --leak-check=full ./<executable>