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Debugging Effectively - SunshinePHP 2017

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Colin O'Dell
Colin O'Dell

Software bugs are inevitable; some are especially difficult to track down, causing you to waste countless hours before throwing your hands up in defeat. It doesn't have to be this way! The mental fatigue and wasted time can be avoided by using strategies like identifying the most-appropriate tool, taking a logical & objective approach, challenging assumptions, listening to variables, isolating the code path, and reinforcing code with automated tests. Attendees will learn how to combine these techniques with the right mindset and attitude in order to debug their code quickly and effectively.

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Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debugging Effectively Colin O’Dell @colinodell
Overview I. Importance of debugging II. Debugging process III. Tools & Techniques IV. Q&A Photo by Roman Boed // cc by 2.0 // https://flic.kr/p/ngwcf1 @colinodell
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective) @colinodell
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective) @colinodell
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective) @colinodell
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m important @colinodell
Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m the single most important skill in programming. @colinodell
Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC PlanningCoding @colinodell
Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC Planning Testing & Debugging Coding @colinodell
Debugging is the process of finding and resolving bugs or defects that prevent correct operation of computer software or a system. – Wikipedia Photo by Stephen Dyrgas // cc by-nc-nd 2.0 // https://flic.kr/p/3eTfWU
Process is the foundation of effective debugging Process Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa
Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Gain experience with code and tools Experience Process
Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Develop a “sixth sense” “Sixth Sense” Experience Process
Junior Developers • Try the “usual” steps • bin/console cache:clear • composer install • chmod –R 777 * • Ask somebody else • Co-worker • Google • StackOverflow post Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL @colinodell
XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X? @colinodell
XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X? •Solution Y might work •How can I do Y? @colinodell
Photo by quattrostagioni // cc by 2.0 // https://flic.kr/p/aGjVq8 1.Don’t parse HTML with regex 2.Solve problems the right way @colinodell
“I don’t know why” “For some reason” “Doesn’t make sense” Photo by Stanley Yuu // cc by-nc-nd 2.0 // https://flic.kr/p/pMnfNu @colinodell
Bugs are logical Photo by Photofest @colinodell
“The bug is not moving around in your code, trying to trick or evade you. It is just siting in one place, doing the wrong thing in the same way every time.” – Nick Parlante, Debugging Zen Photo by GrahamC57 // cc by-nc-nd 2.0 // https://flic.kr/p/cwJi9Q @colinodell
Assume your code is the problem Photo by Sergio Flores Rosales // cc by-nc-nd 2.0 // https://flic.kr/p/5UHkaW @colinodell
Systematic Approach 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0 @colinodell
1. Gather information • Expected behavior vs. actual behavior • Error messages • Stack traces Photo from youmustdesireit.wordpress.com •Screenshots •Browser & OS •Date & time •Log entries @colinodell
2. Replicate the Issue Be able to replicate with 100% certainty Photo by Nick Royer // cc by-sa // https://flic.kr/p/d41ASC @colinodell
3. Identify the Culprit Photo by U.S. Navy // cc 2.0 // https://flic.kr/p/n6Wgks • Be methodical • Make no assumptions • Understand the bug @colinodell
4. Fix it & Re-test • Attempt to replicate again • Avoid XY problem • No temporary workarounds! • Add technical debt • May introduce other issues • Never get replaced with true solutions Photo by Jeff Eaton // cc by-sa 2.0 // https://flic.kr/p/b33rSx @colinodell
5. Mitigate Future Occurrences • Add an automated test • Share your new knowledge • Project documentation • Blog post • StackOverflow • Submit patch upstream Photo by marcokalmann // cc by-nc-nd 2.0 // https://flic.kr/p/4CqLMQ @colinodell
Recap 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0 @colinodell
Long-Term Results • Gain experience • Learn how the system works • Build heuristics • Boost confidence Photo by Glenn Beltz // cc by 2.0 // https://flic.kr/p/i7Csdx @colinodell
Tools & Techniques Photo by Alan // cc by-nc-sa 2.0 // https://flic.kr/p/9azLii @colinodell
Two essential tools • Integrated development environment (IDE) • Interactive debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
Integrated Development Environment •Minimum features: •Syntax highlighting •Auto-completion •Fast code navigation •Debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
Interactive Debugger •Pause code execution •Breakpoints •Conditional breakpoints •Step through execution •Examine variables •Explore call stack Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
@colinodell
Techniques 1. Trace backwards from known issue 2. Trace forwards from start 3. Binary search 4. Use tools 5. Get help 6. Take a break Photo by Massmo Relsig // cc by-nc-nd 2.0 // https://flic.kr/p/pFrJCe @colinodell
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw @colinodell
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
3. Divide & Conquer • Identify different code sections • Set breakpoints at the boundaries • Isolate issue to one particular area • Focus efforts on that area @colinodell
@colinodell
@colinodell
@colinodell
✓ X @colinodell
@colinodell
4. Use tools •Variable dumps •Debug toolbars •Console utility •Profilers •git bisect •netcat •curl •strace •etc. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
Variable dumps Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe •var_dump() •kint() •file_put_contents() @colinodell
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debug toolbars @colinodell
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Console Utility Drupal: drush Drupal Console Symfony: bin/console Magento: n98-magerun Laravel: artisan @colinodell
Performance Profiling Identify slowness: • Bottlenecks • Resource hogs • Inefficient code Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx Tools: • Blackfire (freemium) • New Relic (freemium) • xhprof (open-source) @colinodell
git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
git bisect v1.7 ? ? ? BAD ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
git bisect v1.7 ? ? ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
git bisect v1.7 ? GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
git bisect v1.7 GOOD GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
git bisect v1.7 GOOD GOOD X BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm abcd123 is the first bad commit @colinodell
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe netcat @colinodell
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe curl @colinodell
Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe strace @colinodell
5. Get help • RTFM / RTFD • Project forums or issue queue • StackOverflow, IRC, etc. • Ask a colleague • Expert in that area • Senior developer • Rubber ducking Photo by Hiromitsu Morimoto // cc by-sa 2.0 // https://flic.kr/p/6Vzzaa @colinodell
6. Take a break Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/cFEcDC • Clear your mind; start fresh • Forget invalid assumptions • Recharge your batteries • Let your subconscious work on it @colinodell
Four things to walk away with 1. Computers aren’t random, and neither are bugs 2. Persistence will always pay off 3. Don’t be afraid to dive deep 4. Don’t make assumptions or take things for granted Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/dvEpfY @colinodell
Questions? Photo by Marcello Maria Perongini // cc by-nc-nd 2.0 // https://flic.kr/p/6KDtm @colinodell
Learn More • https://web.duke.edu/cps001/notes/Debugging.pdf • http://www.fiveminutegeekshow.com/20 • http://blog.codeunion.io/2014/09/03/teaching-novices-how-to-debug- code/ • https://www.jetbrains.com/phpstorm/help/debugging.html • http://www.sitepoint.com/debugging-git-blame-bisect/ • http://unix.stackexchange.com/a/50099/80744 • http://codeception.com/docs/01-Introduction • http://chadfowler.com/blog/2014/01/26/the-magic-of-strace/ • http://c2.com/cgi/wiki?RubberDucking Photo by Samantha Marx // cc by 2.0 // https://flic.kr/p/8KrU1R @colinodell
Thanks! Feedback Appreciated! • https://joind.in/talk/a2d4c • @colinodell / colinodell@gmail.com Photo by Steve Rotman // cc by-nc-nd 2.0 // https://flic.kr/p/xiBK

More Related Content

Debugging Effectively - SunshinePHP 2017

  • 1. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debugging Effectively Colin O’Dell @colinodell
  • 2. Overview I. Importance of debugging II. Debugging process III. Tools & Techniques IV. Q&A Photo by Roman Boed // cc by 2.0 // https://flic.kr/p/ngwcf1 @colinodell
  • 3. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective) @colinodell
  • 4. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective) @colinodell
  • 5. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (adjective) @colinodell
  • 6. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m important @colinodell
  • 7. Debugging is... Photo by Ewan Cross // cc by-nc-nd 2.0 // https://flic.kr/p/7MCt3m the single most important skill in programming. @colinodell
  • 8. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC PlanningCoding @colinodell
  • 9. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC Planning Testing & Debugging Coding @colinodell
  • 10. Debugging is the process of finding and resolving bugs or defects that prevent correct operation of computer software or a system. – Wikipedia Photo by Stephen Dyrgas // cc by-nc-nd 2.0 // https://flic.kr/p/3eTfWU
  • 11. Process is the foundation of effective debugging Process Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa
  • 12. Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Gain experience with code and tools Experience Process
  • 13. Photo by Matthew Paulson // cc by-nc-nd 2.0 // https://flic.kr/p/di35xa Develop a “sixth sense” “Sixth Sense” Experience Process
  • 14. Junior Developers • Try the “usual” steps • bin/console cache:clear • composer install • chmod –R 777 * • Ask somebody else • Co-worker • Google • StackOverflow post Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL @colinodell
  • 15. XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X? @colinodell
  • 16. XY Problem Photo by Yoel Ben-Avraham, with changes // cc by--nd 2.0 // https://flic.kr/p/6pmtQL •I want to solve problem X •How do I solve X? •Solution Y might work •How can I do Y? @colinodell
  • 17. Photo by quattrostagioni // cc by 2.0 // https://flic.kr/p/aGjVq8 1.Don’t parse HTML with regex 2.Solve problems the right way @colinodell
  • 18. “I don’t know why” “For some reason” “Doesn’t make sense” Photo by Stanley Yuu // cc by-nc-nd 2.0 // https://flic.kr/p/pMnfNu @colinodell
  • 19. Bugs are logical Photo by Photofest @colinodell
  • 20. “The bug is not moving around in your code, trying to trick or evade you. It is just siting in one place, doing the wrong thing in the same way every time.” – Nick Parlante, Debugging Zen Photo by GrahamC57 // cc by-nc-nd 2.0 // https://flic.kr/p/cwJi9Q @colinodell
  • 21. Assume your code is the problem Photo by Sergio Flores Rosales // cc by-nc-nd 2.0 // https://flic.kr/p/5UHkaW @colinodell
  • 22. Systematic Approach 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0 @colinodell
  • 23. 1. Gather information • Expected behavior vs. actual behavior • Error messages • Stack traces Photo from youmustdesireit.wordpress.com •Screenshots •Browser & OS •Date & time •Log entries @colinodell
  • 24. 2. Replicate the Issue Be able to replicate with 100% certainty Photo by Nick Royer // cc by-sa // https://flic.kr/p/d41ASC @colinodell
  • 25. 3. Identify the Culprit Photo by U.S. Navy // cc 2.0 // https://flic.kr/p/n6Wgks • Be methodical • Make no assumptions • Understand the bug @colinodell
  • 26. 4. Fix it & Re-test • Attempt to replicate again • Avoid XY problem • No temporary workarounds! • Add technical debt • May introduce other issues • Never get replaced with true solutions Photo by Jeff Eaton // cc by-sa 2.0 // https://flic.kr/p/b33rSx @colinodell
  • 27. 5. Mitigate Future Occurrences • Add an automated test • Share your new knowledge • Project documentation • Blog post • StackOverflow • Submit patch upstream Photo by marcokalmann // cc by-nc-nd 2.0 // https://flic.kr/p/4CqLMQ @colinodell
  • 28. Recap 1. Gather information 2. Replicate the issue 3. Identify the culprit 4. Fix it & re-test 5. Mitigate future occurrences Photo from EduSpiral // cc by-nc-nd 3.0 @colinodell
  • 29. Long-Term Results • Gain experience • Learn how the system works • Build heuristics • Boost confidence Photo by Glenn Beltz // cc by 2.0 // https://flic.kr/p/i7Csdx @colinodell
  • 30. Tools & Techniques Photo by Alan // cc by-nc-sa 2.0 // https://flic.kr/p/9azLii @colinodell
  • 31. Two essential tools • Integrated development environment (IDE) • Interactive debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
  • 32. Integrated Development Environment •Minimum features: •Syntax highlighting •Auto-completion •Fast code navigation •Debugger Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
  • 33. Interactive Debugger •Pause code execution •Breakpoints •Conditional breakpoints •Step through execution •Examine variables •Explore call stack Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
  • 35. Techniques 1. Trace backwards from known issue 2. Trace forwards from start 3. Binary search 4. Use tools 5. Get help 6. Take a break Photo by Massmo Relsig // cc by-nc-nd 2.0 // https://flic.kr/p/pFrJCe @colinodell
  • 36. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw @colinodell
  • 37. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 38. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 39. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 40. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 41. 1. Trace backwards •Use a debugger •Identify source of error •Establish context •Work backwards a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 42. 2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 43. 2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 44. 2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 45. 2. Trace forwards •Opposite direction •Problematic line isn’t known •Use debugger or logging a() b() c() d() Photo by Shawn Harquail // cc by-nc 2.0 // https://flic.kr/p/npxFVw
  • 46. 3. Divide & Conquer • Identify different code sections • Set breakpoints at the boundaries • Isolate issue to one particular area • Focus efforts on that area @colinodell
  • 52. 4. Use tools •Variable dumps •Debug toolbars •Console utility •Profilers •git bisect •netcat •curl •strace •etc. Photo by florianric // cc by 2.0 // https://flic.kr/p/c4QJzC @colinodell
  • 53. Variable dumps Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe •var_dump() •kint() •file_put_contents() @colinodell
  • 54. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Debug toolbars @colinodell
  • 55. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe Console Utility Drupal: drush Drupal Console Symfony: bin/console Magento: n98-magerun Laravel: artisan @colinodell
  • 56. Performance Profiling Identify slowness: • Bottlenecks • Resource hogs • Inefficient code Photo by Alan Stark // cc by-sa 2.0 // https://flic.kr/p/dn3qjx Tools: • Blackfire (freemium) • New Relic (freemium) • xhprof (open-source) @colinodell
  • 57. git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
  • 58. git bisect v1.7 ? ? ? ? ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
  • 59. git bisect v1.7 ? ? ? BAD ? ? ? HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
  • 60. git bisect v1.7 ? ? ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
  • 61. git bisect v1.7 ? GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
  • 62. git bisect v1.7 GOOD GOOD ? BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm @colinodell
  • 63. git bisect v1.7 GOOD GOOD X BAD BAD BAD BAD HEAD Photo by unbekannt270 // cc by 2.0 // https://flic.kr/p/oHReqm abcd123 is the first bad commit @colinodell
  • 64. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe netcat @colinodell
  • 65. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe curl @colinodell
  • 66. Photo by Joseph B // cc by-nc-nd 2.0 // https://flic.kr/p/7GAMBe strace @colinodell
  • 67. 5. Get help • RTFM / RTFD • Project forums or issue queue • StackOverflow, IRC, etc. • Ask a colleague • Expert in that area • Senior developer • Rubber ducking Photo by Hiromitsu Morimoto // cc by-sa 2.0 // https://flic.kr/p/6Vzzaa @colinodell
  • 68. 6. Take a break Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/cFEcDC • Clear your mind; start fresh • Forget invalid assumptions • Recharge your batteries • Let your subconscious work on it @colinodell
  • 69. Four things to walk away with 1. Computers aren’t random, and neither are bugs 2. Persistence will always pay off 3. Don’t be afraid to dive deep 4. Don’t make assumptions or take things for granted Photo by Kristina Alexadnerson // cc by-nc-nd 2.0 // https://flic.kr/p/dvEpfY @colinodell
  • 70. Questions? Photo by Marcello Maria Perongini // cc by-nc-nd 2.0 // https://flic.kr/p/6KDtm @colinodell
  • 71. Learn More • https://web.duke.edu/cps001/notes/Debugging.pdf • http://www.fiveminutegeekshow.com/20 • http://blog.codeunion.io/2014/09/03/teaching-novices-how-to-debug- code/ • https://www.jetbrains.com/phpstorm/help/debugging.html • http://www.sitepoint.com/debugging-git-blame-bisect/ • http://unix.stackexchange.com/a/50099/80744 • http://codeception.com/docs/01-Introduction • http://chadfowler.com/blog/2014/01/26/the-magic-of-strace/ • http://c2.com/cgi/wiki?RubberDucking Photo by Samantha Marx // cc by 2.0 // https://flic.kr/p/8KrU1R @colinodell
  • 72. Thanks! Feedback Appreciated! • https://joind.in/talk/a2d4c • @colinodell / colinodell@gmail.com Photo by Steve Rotman // cc by-nc-nd 2.0 // https://flic.kr/p/xiBK

Editor's Notes

  1. PHP developer 14 years JS, Java, C#
  2. What are some words For me: fun challenge
  3. What are some words For me: fun challenge
  4. What are some words For me: fun challenge
  5. Take this one step further Why is that?
  6. How much time coding? 2/3rds
  7. According to the Mythical Man Month, 1/6th ½ is testing/debugging How much - actually writing code vs getting it working Area where it’s worthwhile to become efficient
  8. READ SLOWLY Shouldn’t be done haphazardly
  9. Like intuition, but not Understanding without proof Clarity; accuracy; precision -- Focus on the process Experience and “sixth sense” will come with time NEXT: Debugging process
  10. BE NICE / CONSTRUCTIVE
  11. TODO ADD NOTES
  12. When you give up on the proper approach Apply workaround instead Improper solutions will cause issues later NEXT - EXAMPLE
  13. Base85-encoded Don’t be clever TRANSITION NEEDED!!
  14. Magical thinking
  15. Article sneaky
  16. Bugs are almost always based on faulty assumptions 95% in your code If helping others, assume their code is problem Challenge their assumptions Take with grain of salt
  17. Define the symptoms Collect everything you can
  18. Automated tests preferred, but manual is okay too LEGOS
  19. Understand the fundamental nature Exactly why
  20. Other nice-to-haves: File syncing Git integration Run tools PhpStorm, Sublime Text, vim NOT Notepad++ or Dreamweaver
  21. Debuggers are awesome tool … Better than primitive approaches Examine in real time Xdebug Chrome developer tools
  22. Click 4 times Dive in Look at call stack
  23. Advanced breakpoints Grouping Conditions
  24. Stack trace Grep for error message Set breakpoint For example
  25. Examine variables How did I get here? – call stack
  26. Log/output results at different steps Identify where things start going wrong
  27. Log/output results at different steps Identify where things start going wrong
  28. Log/output results at different steps Identify where things start going wrong
  29. Log/output results at different steps Identify where things start going wrong
  30. Debugger is critical Not only tool Tools are not a substitute for thinking
  31. Phpunit Phpspec behat
  32. Scales logarithmically – runs in O(log N) 9 commits - 4 tests 10x: 90 commits – 8 tests 100x: 900 commits - 16 tests
  33. END TOOLS SECTION
  34. Fifth technique
  35. 1. There is ALWAYS a logical explanation 3. Great learning opportunity 4. Challenge everything
  36. ? Other Questions? Talk afterwards or contact me
  37. Thank you guys I’d appreciate feedback