Other Debugging Tools

Question 1

Log Files

Answer 1

• files containing text and values written out by programs as they execute
• can be gathered over a long period of time
• can gather information in a production system.
• good for working with distributed programs

Question 2

Log4c

Answer 2

• our own logging system
• Has 3 levels of logging severity
  error: very important, major problems
  warning: must read, something is wrong
  info: informational message
• Can Be
  
  • Filtered to write only messages of higher than a given severity
  • Can be enabled and disabled
  • Can auto flush to make sure output or not to increase efficiency

Question 3

Assertions

Answer 3

• access assertions: #include <assert.h></assert.h>
• Added to production systems to stop program when something goes very
  wrong
• Tells the programmer the impossible happened and needs to be fixed
• assert(logical condition)
  -If the condition is triggered, the assert fires.

Question 4

Lint

Answer 4

• check source code for many possible errors
• can give clues about the source of a bug
• Available for many languages
• more sensitive than a compiler & points out potential source errors compiler might miss
• might yield higher quality source code

Question 5

Core Dumps

Answer 5

• older debugging technique
• makes copy of all of the memory allocated for program and writes it to a file
• information is in binary, very laborous
• can use automatic dump readers which can allow you to explore these files in a more human readable way

Question 6

Conditional Compilation

Answer 6

define DEBUG

• can turn debugging on and off by simply changing the value of the DEBUG macro

…
#ifdef DEBUG
printf(“%s(%d):z$d\n”,FILE,LINE,z);
#endif

• uses preprocessor directives to include or exclude code from the build based on the value of a macro

Question 7

Debug and Release Builds

Answer 7

Debug builds
- do more checking of error conditions
- in debug mode, code is compile such that:
- it does not optimize the code to make it as fast as possible
- it might include additional runtime checks

Release Builds
- faster but dont do checking

Question 8

Compiled vs Interpreted

Answer 8

Compiled
- compiler goes through the whole program at once before it runs
- Detects problems before the program ever runs

Interpreted
- Program is run line by line
- Program is parsed only just before line is executed
- Problems are not detected until line is executed
- Rarely executed lines can make it to production with bugs in them because they were never executed

Question 9

Strongly Typed vs Weakly Typed

Answer 9

Strongly Typed
- All assignments and function calls are check to make sure the right types are used
- Errors detected at compilation time

Weakly Typed
- Variables and parameters can accept any type
- Type mismatches may not be detected until runtime.
- Errors in infrequently executed lines may remain undetected for a long timer.