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62 lines
2.0 KiB
Markdown
62 lines
2.0 KiB
Markdown
---
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title: Debugging
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---
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# Debugging
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removing technical faults
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isolaing and remove technical faults
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a human process
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- requires creativity/disipline/knowledge
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- deepr understanding of code
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debuggers are tools to help debugging
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## 1 common approaches
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temporarily add output of diagnostic info
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- "printf" debugging
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permanently include calls to logging system
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- route to terminal, log files etc
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## 2 debugging machine code
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- cpu runs code instruction by instruction
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- thus debugger can intervene between instructions
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- most cpus help debugger interrupt and resume programs
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- cpu reached current code via a sequence on callers
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- called **stack trace** , aka back frame, stack frame etc
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- may reach point where it cannot continue
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- e.g., integer division by zero, program execution must stop
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- stack trace of stopped program can be analysed
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## 3 Imperative languages
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These are language that are executed in a step-wise, sequentail manner.
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- debug symbols
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- e.g., method named, variable named
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- source code context
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- line numbers
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- variable name
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- function method names
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## 4 doing debugging
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### 4.1 stepping skipping running
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- step into --> steps one statement and steps into function calls
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- step over --> a step that treats function calls as statement
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- step out --> return to the instruction after the function call you're in
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- continue --> go back to running code continuously
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### 4.2 controlling debugger execution
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Can run normally --> debugger wil run when program crashes
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Set Breakpoint --> debugger will stop program when/if that line is reached
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- conditional breakpoints only suspend if a condition is true
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Watch point --> program is suspended when some data changes (e.g., variables)
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## 5 debugging non imperative languages
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e.g, spreadsheet (Dataflow programming)
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- no breakpoints
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- must step through _iterations of computations_
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e.g., Equation
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- break into smaller parts
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- try 'compile' it in multiple ways
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e.g., Data base query (declarative programming)
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- -reexpressign the query and comaring can be useful |