size of returning pointer

[anuvanand1]

i have a fn of type
short* funname (char*)

when i call this function it returns short array
how to find the the size of that returned array

[DumRat]

i have a fn of type
short* funname (char*)

when i call this function it returns short array
how to find the the size of that returned array

You can't. Return an object instead. Or pass another param by reference
to the function to get the size. I don't know which is the better of these two methods.

[mac11]

Another common way of doing it (especially in C) is to supply the buffer and size of that buffer to the function and have it just fill the buffer rather than allocate it.

Also, this way the caller is less likely to forget that he needs to deallocate the buffer.

[Studlyami]

Creating an array in a function then returning the array is dangerous. The array will go out of scope as soon as the function ends, so there is no guarantee that the pointer will still be pointing to valid data. If you need to fill an array in the function pass the array into the function and use it.

[dharanidhar]

can can declare that array as global variable?so that it's scope never ends with the function...

[Studlyami]

can can declare that array as global variable?so that it's scope never ends with the function...

you COULD, but shouldn't. Before weakness gets to post this link i will.

[Ganon11]

If you allocate memory for the array (using malloc/new/whatever) and return a pointer to it, it should remain valid in any scope. Just remember to free()/delete that pointer eventually.

[Savage]

If you allocate memory for the array (using malloc/new/whatever) and return a pointer to it, it should remain valid in any scope. Just remember to free()/delete that pointer eventually.

How it should?

e.g

void *Func(void)
{
 void *p=malloc(10);
 return p;
}

Here p is in data zone of Func,but it points to the beginning of some memory segment on the heap,when function exits data zone is deallocated and therefore
p is no more.How are you going to find address of that memory block?

[Ganon11]

You're right that p doesn't exist, but your return value will carry the value of p back to wherever it was called. What is the value of p? The address of that block of memory. So the block of memory was created and still exists, and you can get the address of it by capturing the return value of your function, but p itself no longer exists (remember p was just a local variable allocated on the stack).

[Studlyami]

your return value will carry the value of p back to wherever it was called. What is the value of p? The address of that block of memory. So the block of memory was created and still exists,

After the return you know where the structure begins, but you don't know how many values are in it. In order to avoid that you will need to do what DumRat suggested and pass in an int by reference to get the size of the array.