Week 12 - Debugging

Why is debugging important?

• Helps trace code execution and understand lower abstraction levels.

• Validates assumptions, verifies data, and memory.

• Essential for finding and fixing bugs.

What is a debugger?

• An external tool to inspect program execution and runtime properties, like:

  • Memory, variables, objects, threads, registers, and call stacks.

• Requires language support (e.g., debug symbols like DWARF).

• More efficient than using print statements.

When should you use a debugger vs. printing/logging?

• Use a debugger during development to inspect code execution.

• Use printing/logging when a debugger is unavailable (e.g., in production or on player devices).

What is the #1 feature of a debugger?

The ability to pause program execution at specific points using breakpoints.

Can be achieved in various ways, but typically by setting breakpoints

What are breakpoints?

• Points in the source code where the debugger halts execution for introspection.

• Useful for examining threads, variables, and call stacks.

What is a halted context?

The state of the program when execution is paused, allowing you to inspect:

• Threads, call stacks, local variables, objects, and registers.

What is a call stack?

• Shows how the program reached the current line of code.

• Includes the sequence of function calls and the current thread.

What are watchpoints?

• Advanced breakpoints that pause execution when:

  • Specific variables or memory accesses meet conditions (e.g., variable <= 5).

• Supported in tools like VSCode and Chrome debugger.

How do breakpoints work under the hood?

• Software Breakpoints: Replace an instruction with a trap that interrupts the program.

• Hardware Breakpoints: Use dedicated CPU registers to halt execution.

What is DWARF in debugging?

(DWARF):

• Converts program memory and addresses into source code and variables.

• Requires compiler flags like -g for languages like C/C++, Rust, or Swift.

difference between breakpoint and watchpoint?

A breakpoint hits every game hits, watchpoint only hits when a condition happens

What are the steps a debugger can perform during a halted context?

• Step to the next line of code.

• Step into a function call.

• Return to the calling function.