c.md

C Command Line Debugging Cheatsheet

Help

• List available command classes from the debugger: help
• List available commands in a class from the debugger: help <class_name>
• List all available commands from the debugger: help all

Start the debugger

• Compile your source with the gcc -g option: $ gcc -g -o <bin_name> <source>
• Run the debugger: $ gdb <bin_name>
• Start the program in the debugger until the first breakpoint or completion: run (abbr r)
• Start the program in the debugger until the main procedure: start

Attach the debugger

$ gdb -p <pid>

pid can be found by running ps -aux | grep <bin_search>

Breakpoints

• Set static/code breakpoints:

#include <signal.h>
/* ... code ... */
raise(SIGINT);

In gdb when this breakpoint is hit, the top of the stack is the libc shared object file. Go up a frame in the stack from gdb by running up

• Set static/code conditional breakpoints: same as above, but with a conditional statement surrounding the raise() call

💡 The following commands pertain to the debugger when a breakpoint is met or code is paused

• Set a breakpoint on the current line: break (abbr b)
• Set a breakpoint on line_number in the current file: break <line_number> (abbr b <line_number>)
• Set a breakpoint on line_number in file_name: break <file_name>:<line_number> (abbr b <file_name>:<line_number>)
• Set a breakpoint on a function: break <function_name> (abbr b <function_name>)
• Set a breakpoint on a function in a file_name: break <file_name>:<function_name> (abbr b <file_name>:<function_name>)
• Remove a breakpoint: delete <breakpoint_number>
• List all breakpoints: info break (abbr info b)

Control

💡 The following commands pertain to the debugger when a breakpoint is met or code is paused

• Continue until next breakpoint: continue (abbr c)
• Step to the next statement in the current function: next (abbr n)
• Step in to the next statement or into the next function: step (abbr s)
• Step out of the current function on the stack: finish (abbr f)
• Continue to given location: advance

Analysis

💡 The following commands pertain to the debugger when a breakpoint is met or code is paused

• List the current source: list (abbr l)
• Run an expression in the current context: print <expr> (abbr p <expr>)
• Watch an expression: watch <expr>
• List the current stacktrace: backtrace (abbr bt)
• Go up one frame in the stack (the one that ran the current frame): up
• Go down one frame in the stack (the one called by the current frame): down

Global control

• Terminate the program: kill
• Terminate the program and exit the debugger: quit (abbr q)