Chapter 18 - Debugging

phase

Testing ________ has two parts: prep, develop and execute tests (testing), if output unsuccessful- failure- new goal to find and remove bug (debugging)

Memory dump

________: printout of all registers and relevant memory locations is obtained and studied, slow and inefficient- hard to link back to source program, lots of data, only see state at one instant in time.

debugging

process of identifying failure, tracing bug, locate errors causing it and fixing the errors

watch points

see value of variables at particular points in time, use output statements, breakpoint execution

breakpoint categories

unconditional (inserted & execution stops here), conditional (if expression True, stop), temporary (happens once), internal (set by debugger)

single stepping

watch each executable line of code

backtracking

observe failure, find site of symptom of failure, trace back to highest abstraction in design collecting all code related to this, slowly isolate module using dataflow and find the bug (if you understand program logic it is effective

debugging guidelines

fresh thinking leads to good debugging (dont spend hours, take a break), dont isolate the bug from you colleagues (discuss the problem), dont modify code on first attempt, add test cases, regression testing is a must, design should be referred to before fixing the error

debuggers

illustrate dynamic nature of program, understand the program as well to find bugs, control the application to make it easier to test

types of debugging

kernel debugger, basic machine-level debugger, interpretive programming environment debugger