Pointers and Dynamic Memory

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Pointers and Dynamic Memory

• Dr. Ying Xie

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• Dynamically Allocate Memories
• Memory allocation operator new
• int p1 new int
• int p2 new int(2)
• int p3 new int10
• Memory deallocation operator delete
• delete p1
• delete p2
• delete p3

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• Memory Leaking
• void myfunction()
•     int pt    int ordinaryVariable    pt
  new int(1024)    ....    ....    //No
  delete
• int main()
•     while (some condition exists) //
  Pseudo-code            myfunction()        
  exit 0

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• Memory Leaking (1)
• //wrong version which cause memory leaking
• void myfunction()
•     int pt    int ordinaryVariable    pt
  new int(1024)    ....    ....    //No
  delete
• int main()
•     while (some condition exists) //
  Pseudo-code            myfunction()        
  exit 0

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• Memory Leaking (2)
• //correct version
• void myfunction()
•     int pt    int ordinaryVariable    pt
  new int(1024)    ....    ....    delete pt
• int main()
•     while (some condition exists) //
  Pseudo-code            myfunction()        
  exit 0

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• Dangling Pointer (1)
• //wrong version that causes the dangling pointer
  problem
• int PP new int(10)delete P
• P 5

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• Dangling Pointer (2)
• //correct version
• int PP new int(10)delete PP 0