quartz/content/notes/debugging.md

title	tags
debugging	cosc202

removing technical faults isolaing and remove technical faults a human process

• requires creativity/disipline/knowledge
• deepr understanding of code

debuggers are tools to help debugging

1 common approaches

• temporarily add output of diagnostic info -> "printf" debugging
• permanently include calls to logging system -> route to terminal, log files etc

2 debugging machine code

• cpu runs code instruction by instruction
  • thus debugger can intervene between instructions
  • most cpus help debugger interrupt and resume programs
• cpu reached current code via a sequence of calls
  • called stack trace , aka back frame, stack frame etc
• may reach point where it cannot continue
  • e.g., integer division by zero, program execution must stop
  • stack trace of stopped program can be analysed

3 Imperative languages

These are languages that are executed in a step-wise, sequentail manner using the imperative programming paradigm

• debug symbols
  • e.g., method named, variable named
• source code context
  • line numbers
  • variable name
  • function method names

4 doing debugging

4.1 stepping skipping running

• step into --> steps one statement and steps into function calls
• step over --> a step that treats function calls as statement
• step out --> return to the instruction after the function call you're in
• continue --> go back to running code continuously

4.2 controlling debugger execution

Can run normally --> debugger will run when program crashes

Breakpoint --> debugger will stop program when/if that line is reached

• conditional breakpoints only suspend if a condition is true

Watch point --> program is suspended when some data changes (e.g., variables)

5 debugging non imperative languages

e.g, spreadsheet (Dataflow programming)

• no breakpoints
• must step through iterations of computations

e.g., Equation

• break into smaller parts
• try 'compile' it in multiple ways

e.g., Data base query (declarative programming)

• -reexpressign the query and comaring can be useful