Checking if a pointer is allocated memory or not

Question

Can we check whether a pointer passed to a function is allocated with memory or not in C?

I have wriiten my own function in C which accepts a character pointer -

Answer 1

Well, I don't know if somebody didn't put it here already or if it will be a possibility in your programme. I was struggling with similar thing in my university project.

I solved it quite simply - In initialization part of main() , after I declared LIST *ptr, I just put that ptr=NULL. Like this -

int main(int argc, char **argv) {

LIST *ptr;
ptr=NULL;

So when allocation fails or your pointer isn't allocated at all, it will be NULL. SO you can simply test it with if.

if (ptr==NULL) {
  "THE LIST DOESN'T EXIST" 
} else {
  "THE LIST MUST EXIST --> SO IT HAS BEEN ALLOCATED"
}

I don't know how your programme is written, but you surely understand what am I trying to point out. If it is possible to check like this your allocation and then pass your arguments to you function, you could have a simple solution.

Of course you must be careful to have your functions with allocating and creating the structure done well but where in C you don't have to be careful.