This document provides tips for using advanced commands and features in the LLDB debugging tool. It explains how to use print commands, declare variables, add breakpoints, view thread backtraces, inspect registers, look up private APIs, and more. The goal is to demonstrate higher-level LLDB gestures that make debugging more powerful and efficient.

1. DEBUG 裝屌指南
那些看起來來⾼高級的LLDB⼿手勢
Pofat

2. Pofat Tseng
iOS, Product,
UX, Triathlon & Coffee

3. LLDB與我（的前兩兩年年）

7. Compiling was like…

8. 換到Swift 後…

9. Print Commands
• p , print, call : expression —
• po: expression -O —

10. Not Only ‘Print Commands’

11. 縮寫到唯⼀一配對即可
• 以下兩兩者等價

12. 可宣告變數
$開頭之變數可存在於 lldb 的空間

13. 可宣告變數

14. 需要指定型別

15. 需要指定型別
ObjC
Swift

16. 流程控制

17. 流程控制

18. thread backtrace

19. 圖⾃自 http://condor.depaul.edu/slytinen/406s16/ch3.html

20. 圖⾃自 http://condor.depaul.edu/slytinen/406s16/ch3.html

21. Frame

22. Breakpoints
• -n : func or symbol name
• li : list all breakpoints

23. help & apropos

24. Who did this?

25. Print? Think again!

26. Print? Think again!
鄉⺠民故事你敢信？
明天要上線，merge後的code 不知道怎麼了了
覆寫了了某個 customs view 的 _layer

28. Print? Think again!
Watchpoint

29. Better way to log

30. Better way to log maybe
• Breakpoints will minimize the affect to flow
• Need a way to import/export breakpoints

31. UI 操作 - present VC

32. UI 操作 - view hierarchy

33. Viva la Python

34. .lldbinit
~/command.py
~/.lldbinit

35. Chisel

36. Chisel
• border

37. Chisel
• visualize

38. Chisel
• bmessage

39. Chisel in Swift context
• error: error: use of undeclared identifier ‘CGFloat'
• CGFloat is defined by macro in objc. In Swift, it’s not.

40. Target
~/.lldbinit

41. 圖 by David Lin

42. Image lookup

45. Image lookup
• 可找私有 API
• 也可在 lldb 裡做 method swizzling

46. Image lookup
• 可找私有 API
• 也可在 lldb 裡做 method swizzling

47. Registers
• $rip : Current instruct pointer
• $rdi: First argument
• $rsi, $rdx, $rcx, $R8, $R9: Second, third, forth, fifth and
sixth arguments
• Others will be on stack

48. Registers
• $rip : Current instruct pointer
• $rdi: First argument
• $rsi, $rdx, $rcx, $R8, $R9: Second, third, forth, fifth and
sixth arguments
• Others will be on stack

49. Registers
• $rsp : head of current frame ( head is smaller than
bottom)
• $rbp: bottom of current frame
• $rax: Return register

50. Registers
圖⾃自 http://condor.depaul.edu/slytinen/406s16/ch3.html

51. 圖⾃自 http://condor.depaul.edu/slytinen/406s16/ch3.html

52. Witness “Witness
Table”

53. Witness “Witness Table”
legs: 8
heads: 2
Metadata
Witness Table

54. Witness “Witness Table”
legs: 8
heads: 2
Metadata
Witness Table
walk()

55. Output all current state

56. 解放你的⾖豆腐頭

57. 全⾯面command line 啦

60. Which one is better?

61. Reference
• Dancing in the Debugger - A waltz with LLDB
• 泊學（很精實的中國教學網站）
• WWDC 2014 Session 410 : Advanced Debugging in LLDB

62. 感謝各位