SizeOf function

This is a discussion on SizeOf function within the C Programming forums, part of the General Programming Boards category; Hi everyone, i'm just starting out with C, and i'm not too sure how to use the SizeOf Function, I ...

  1. #1
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    Question SizeOf function

    Hi everyone, i'm just starting out with C, and i'm not too sure how to use the SizeOf Function, I need to use it to verify that an inputted integer is not greater than the maximun number of bytes allowed....and i don't know how to do this...i've done this:
    if ((sizeof(digit) > 655536) || (digit==NULL))
    printf("ERROR: That is too large an integer");

    but I know that's wrong cuz i get this msg:

    getData.c:12: warning: comparison between pointer and integer

    if you could help me I'd be so greatful,
    thanks eveyone!
    from Mel

  2. #2
    Registered User Cela's Avatar
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    >>and i'm not too sure how to use the SizeOf Function, I need to use it to verify that an inputted integer is not greater than the maximun number of bytes allowed
    First things first, sizeof isn't a function, it's an operator :-) And it returns the number of bytes of the object you pass to it, not the maximum value that can be held by those bytes. So your problem could be solved like this
    Code:
    #include <stdio.h>
    
    int main(void)
    {
      if (sizeof(int) > 2)
        /* Only allow the minimum integer size */
      {
        fprintf(stderr, "Fatal error: Integer size too large\n");
      }
    
      return 0;
    }
    *Cela*

  3. #3
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    Re:

    would that still work in my function?
    cuz I dont' want to put that in my main method



    I tried, what you said, and now I get this warning

    getData.c:14: warning: passing arg 1 of `printf' from incompatible pointer type
    thanks eveyone!
    from Mel

  4. #4
    Registered User Cela's Avatar
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    >>would that still work in my function?
    Sure, just paste it into your function and you're set :-)

    >>getData.c:14: warning: passing arg 1 of `printf' from incompatible pointer type
    It looks like you're trying to use printf with fprintf arguments. fprintf takes an output stream as it's first argument, try changing it to
    Code:
    printf("Fatal error: Integer size too large\n");
    *Cela*

  5. #5
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    thanks!

    thanks a lot for your help!
    thanks eveyone!
    from Mel

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