What is lldb and why are we using it? lldb is an interactive debugging tool, similar to gdb (gnu debugger). It is useful when finding bugs or debugging in C/C++. The reason why I use lldb is simple because gdb does not work on MacOS (Apple Silicon).

It catches the segmentation fault better than just running the test cases. Segmentation fault or segfault happens when an OS tries to access a restricted area of memory. In other words, it happens due to error involved with pointers, malloc / calloc, free etc.

I found it very useful when I tried to debug an segfault error caused by dereferencing a null pointer.

For a simple guide, after setting up lldb, compile with -g flag or build. Then, run the command “lldb ./

" to use the tool. If you are getting "invalid target" error, then it means you are not specifying the output/object file.

• Start lldb: ‘'’lldb ./test’’’
• Set a break point: ‘'’b .c:<line#>'''
• run: ‘'’r’’’
• Step into: ‘’’ s ‘’’
• Step over: ‘’’ n ‘’’
• Back trace: ‘'’bt’’’
  • back trace is a record that shows application’s movement in stack form
• Frame: ‘'’f’’’
  • Select frame 9: ‘'’f 9’’’

You can type ‘'’help’’’ to look up more commands or this link to compare with gdb commands.