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Pointer and reference similar at assembly level

Discussion in 'C' started by kaustubh, Aug 15, 2007.

  1. kaustubh

    kaustubh New Member

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    Pointer and reference maybe same at assembly level.
    Try an experiment :

    Code:
    # include<stdio.h>
    int main()
    {
      int i =90;
      int *pointer;
      int &reference = i; // Line 6
      pointer = &i;  
      return 0;  // Line 8
    }
    compile it to assembly with Microsoft c++ like this :
    Code:
    c:\ cl /Fa filename.cpp
    or with gcc like
    Code:
    c:\ gcc -S -masm=intel filename.cpp
    Open the asm file like c:\ notepad filename.asm

    Now you can the code of i, pointer, and reference;

    Code:
     Line 6
    	mov	DWORD PTR _i$[ebp], 90			; int i = 90;
    ; Line 8
    	lea	eax, DWORD PTR _i$[ebp]                  ; int &reference = i;
    	mov	DWORD PTR _reference$[ebp], eax
    ; Line 9
    	lea	ecx, DWORD PTR _i$[ebp]               ; int *pointer
    	mov	DWORD PTR _pointer$[ebp], ecx    ;  pointer = &i;
    
    you see the code for pointer is exactly same as reference .
     
  2. DaWei

    DaWei New Member

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    That's because C doesn't have references like C++. The & is strictly an address-of operator.
     
  3. shabbir

    shabbir Administrator Staff Member

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    He is using a cpp file and so the compiler is C++.
     
  4. kaustubh

    kaustubh New Member

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    Dawei i am using c++ compiler if you don't believe me see this code

    Code:
    #include<iostream>
    
    int main()
    {
    int i =90;
      int *pointer;
      int &reference = i; 
      pointer = &i;  
      return 0;  
    }
    
    
    Code:
    	
           mov     DWORD PTR _i$[ebp], 90			;  int i = 90
    
    	lea	eax, DWORD PTR _i$[ebp]                  ; int &reference = i; 
    	mov	DWORD PTR _reference$[ebp], eax
    
    	lea	ecx, DWORD PTR _i$[ebp]                  ; pointer = &i;
    	mov	DWORD PTR _pointer$[ebp], ecx
    	
    
    the code of reference is same as code of pointer.
     
  5. rajkumar_singhalmca

    rajkumar_singhalmca New Member

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    the pointer is very ueful when the use in the right way otherwise it can be damaged the our memory location.
     

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