size of dynamic array

Hi, i have the following program:

Code:

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#include <stdio.h>
#include <stdlib.h>

int main(){

        int *test, i;
        int test2[5] = {1,2,3,4,5};

        test = malloc(5*sizeof(int));

        //populate dynamic array with arbitary data
        for(i=0; i<5; i++){
               
                test[i] = i+1;
                printf("test[%d] = %d\n", i, test[i]);
               
        }

//OUTPUT 1
        printf("sizeof test  = %d\n", sizeof(test));

//OUTPUT 2
      printf("sizeof test2 = %d\n", sizeof(test2));

}

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The OUTPUT 1 returns the size of test (the dynamically allocated array) to be 4 and OUTPUT 2 returns test2 as 20. Surely they should both be the same (ie 20) as they both hold 5 elements each:confused:. Or is there a different way for establiching the size of a dynamic array?

thanks i advance.

tg

Quote:

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Originally Posted by tommy_gunn

Or is there a different way for establiching the size of a dynamic array?

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You know the size when you ask for it -- keep track of it if you want it elsewhere.

test2 is an array and sizeof() returns the real size of it.

test1 is a pointer, and that's what sizeof() returns: the size of a pointer on your platform.

There is no way to get the size of the allocated memory from the pointer. That's why functions like gets() are so dangerous. You pass a pointer to a buffer and gets() has no way of knowing how big that buffer is.

Quote:

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Originally Posted by Dave_Sinkula

You know the size when you ask for it -- keep track of it if you want it elsewhere.

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Kool - thought it mite be sumtin like that. thanks for clearing it up for me.

tg