asked on

Explaination

Hi all,

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

void check( int * &ptr)
{
      int *tmp;

      tmp = (int*)malloc(sizeof(int));
      *tmp= 100;
      ptr= tmp;

      printf("in check is %d\n",*tmp);

}

void main ()
{
      int* t;

      check(t);

      printf("value is %d\n",*t);
}
/*
in check is 100
value is 100
Press any key to continue
*/

I just wonder that the tmp in chec() is a local variable. So have can its value still valid for t in main() , even though i know ptr = tmp. Please explain me the
check (int * &ptr) vs check( int *ptr). More examples are appreciated.
Thanks.

Axter

Hi valleytech,
> Please explain me the check (int * &ptr).
That is not C code, and instead that is C++ code.
In C++ that's a reference to a pointer, and it allows it to change the calling functions variable as to what it's pointing to.
You can't do that with C unless you use a pointer to a pointer.

Cheers!

SOLUTION

Axter

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valleytech

ASKER

Hi Axter,
How can the local variable still there after exit the check(). So far I know that local variable only still avaible if i use static.
One more thing, if i use
printf("value is %d\n",t) ---> it doesn't work. COuld you please explain line by line? Thanks a lot.

ASKER CERTIFIED SOLUTION

Kent Olsen