pointers

This is a discussion on pointers within the C Programming forums, part of the General Programming Boards category; okay a pointer is a variable that points to another variable address ..right ??. i have written thids code and ...

  1. #1
    Registered User datainjector's Avatar
    Join Date
    Mar 2002
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    356

    pointers

    okay a pointer is a variable that points to another variable address ..right ??.

    i have written thids code and it allocats 1 char right that means 1 byte

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int main()
    {
     char *sp;
    
     sp = malloc(1);
    
     strcpy(sp, "datainjector" );
     puts(sp);
     free(sp);
    
    
          system("PAUSE");
          return 0;
    }
    I allocated 1 byte space to pointer sp then it shoudl only contain d ??? Okay first of all a pointer is a varible so if i use molloc to allocate space i can use it as a variable or if i dont allocate space i can use it as a pointer ??
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  2. #2
    ATH0 quzah's Avatar
    Join Date
    Oct 2001
    Posts
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    Code:
     char *sp;
    
     sp = malloc(1);
    
     strcpy(sp, "datainjector" );
     puts(sp);
    Are you intentionally trying to crash your computer, or what exactly?

    1) 'puts' is a string function.
    2) string funtions require that the string be null terminated.
    3) Thus, if you treat 'sp' as a string, it MUST contain a null. As such, a single character won't suffice.
    4) strcpy does not do any boundry checking.
    5) As such, it just merrily copies off the end of your allocated space, and over whatever happens to be there.

    1) Use strncpy.
    2) Stop trying to crash your comptuer. It'll like you better.


    Quzah.
    Hope is the first step on the road to disappointment.

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