How do you use LLDB commands for diagnosing and troubleshooting code errors?

LLDB is a debugger that allows step-by-step execution of code, viewing variable values, and analyzing the application's state during runtime. For diagnosing and fixing errors in iOS code, the following LLDB commands are often used:

• breakpoint set -n functionName — set a breakpoint at a function.
• breakpoint set --file FileName.swift --line 42 — set a breakpoint at a specific line.
• run — start the application under the debugger.
• step or s — execute the current line and step into the function.
• next or n — execute the current line and move to the next, without stepping into functions.
• continue or c — continue execution until the next breakpoint.
• frame variable or fr v — display the values of local variables in the current stack frame.
• expression or expr — evaluate an expression or change a variable's value during debugging.

Example usage:

(lldb) breakpoint set --file ViewController.swift --line 25
(lldb) run
(lldb) frame variable
(lldb) next
(lldb) expression someVariable = 10
(lldb) continue

Thus, LLDB helps understand where and why an error occurs, explore the program's state, and test hypotheses about the causes of crashes.