The Corner of Coding

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The Corner of Coding

• con su amigo
• Luke Wagner

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Debug, _DEBUG, and debugging

• Debugging shouldnt be a crutch, but sometimes
  its majorly useful.
• Debug means several things in different
  contexts, important to know what they are

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The Preprocessor

• Conditionally compiled code for extra checking at
  a performance cost
• ifdef _DEBUG
• if (expensive_validity_check())
• endif
• Traditionally, _DEBUG
• You can have pass global defines to the
  compiler cl.exe /D _DEBUG test.cpp

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The Preprocessor

• Great for checking things you never ever ever
  expect to go wrong, everywhere.
• ifdef _DEBUG
• define assert(exp) / do a check here /
• else
• define assert(exp) __noop
• endif
• However, not a replacement for real error handling

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debugging

• Process that uses special OS features to help the
  programmer
• Attaching a debugger for
• stepping, call stack, checking values,
  breakpoints, first/second chance exceptions, etc
• You can attack debugger to arbitrary processes

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debugging

• Symbols the keys to the kingdom

Cowspeed 100000Cowangry true
Debugger
01100100100100100111001100101010010101010100101010
010010
Debugged process
Symbols
struct Cow int speed bool angry
double yipe
int foo
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debugging with Visual Studio

• Compilation produces .exe and .pdb (Program
  Debug Database)
• To debug AND use symbols
• Same absolute location
• Same directory
• A bunch of other places

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debugging with Visual Studio

• Most important trick ever
• Tools?Options?Debugger?Native?Load DLL Exports
  true
• Solution Proprties?Common Properties?Debug Symbol
  Files
• Add this path
• srvc\some_pathhttp//msdl.microsoft.com/downloa
  d/symbols
• See symbols loaded (or not) with these on or off
• Debug?Windows?Modules
• Public symbols for C/C runtime Win32

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Lastly

• Build settings (Debug or Release are common
  defaults)
• Optimization (makes symbols quirky, possibly
  expose optimizer bugs (rarely))
• Which libraries you link to
• Language features settings
• Test environment working directory, attach
  debugger or not

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I much prefer to assumpt()
define assumpt(exp) assert(true)
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Youre not serious are you?
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• What will happen next??
• Will Danny eat the cute little puppy?!!
• Find out next week