C++ debugging basics

A debugger allows to intervene in a program, to continue or to examine variables at a breakpoint or watchpoint. For example, to fix a seqfault of the program. The program must be compiled with debug symbols.

Start lldb program-name or run lldb and create a target create program-name.

to start the program in lldb:

• process launch or alias run, r
• or connect it to a process by process id or process name.

When it is running:

1. s step into
2. n next
3. f finish

• help
• bt backtrace

Interactive debugging

Example using lldb for a program called sdl-beatbox with CMake. CMake ensures that the program is built with -g for lldb or gdb.

1. mkdir Debug && cd Debug
2. cmake -DCMAKE_BUILD_TYPE=Debug ..
3. make
4. lldb sdl-beatbox
5. breakpoint example b main
   • on symbol: b Au<tab>
   • or on line: set breakpoint -f <filename> -l <line number> or b sequencer.cpp : 43
6. r to launch.

lldb gui

In the lldb session, gui leads to the graphical user interface.
In the gui, a diamond shows the current line and allows navigation with arrow keys and checking the status.

Links

1. lldb tutorial
2. lldb for gdb users