LLDB

Tips on using LLDB

Transcript

1. LLDB
   Khoa Pham - 2359 Media
   

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2. LLDB
   Home page http://lldb.llvm.org/
   LLDB is an open-source debugger that features
   a REPL, along with C++ and Python plugins
   

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3. Menu
   - Command
   - Use cases
   - Python
   - Chisel
   - Standalone
   

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4. Command
   

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5. Command - help
   Information on any command
   help print
   help thread continue
   help help
   

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6. Command - print
   Print value
   print a
   print self
   

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7. Command
   Prefix matching
   print, prin, pri, p
   expression, e
   Can’t use
   pr (print or process?)
   

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8. Command
   $ variable
   Anything starting with a dollar sign is in LLDB’
   s namespace and exists to help you
   print $0 + 7
   

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9. Command - expression
   Evaluate an expression (ObjC++ or Swift) in the
   current program context,
   Modify values in the program
   expression $0 = 10
   e $0 = 10
   

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10. Command - print
    'print' is an abbreviation for 'expression --'.
    Use -- to signify the end of the flags and the
    beginning of the input
    e --location -- -count
    

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11. Command - print object
    See the description method of an object
    e -O -- aString
    po aString
    

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12. Command - variable
    The variable must start with a dollar sign
    e NSInteger $b = 10;
    p $b + a
    

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13. Command - flow
    Continue
    process continue, continue, c
    Step over
    thread step-over, next, n
    

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14. Command - flow
    Step into
    thread step-in, step, s
    Step out
    thread step-out, finish
    

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15. Command - thread return
    Executes the return command, jumping out of
    the current stack frame
    thread return YES
    

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16. Breakpoint
    List breakpoints
    br li
    Create breakpoints
    br set -f ViewController.m 39
    

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17. Use cases
    Find targets of a button
    po [self.myButton allTargets]
    

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18. Use cases
    See the frame
    po self.view.frame
    e @import UIKit
    po self.view.frame
    

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19. Use cases
    Change background color without continue
    e self.view.backgroundColor = [UIColor greenColor]
    e (void)[CATransaction flush]
    

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20. Use cases
    Watch variable
    wivar self _number
    

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21. Python
    LLDB has full, built-in Python support. If you
    type script in LLDB, it will open a Python REPL
    

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22. .lldbinit
    Executed every time LLDB starts
    command script import /path/to/fblldb.py
    

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23. Chisel
    brew update
    brew install chisel
    # ~/.lldbinit
    command script import /path/to/fblldb.py
    

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24. Standalone
    Using LLDB as a Standalone Debugger
    

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25. References
    - Getting Started with LLDB
    - Dancing in the Debugger — A Waltz with LLDB
    - Video Tutorial: Using LLDB in iOS
    - Navigating and discovering an iOS codebase using lldb
    - chisel
    

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