C , Error: Expression must be a modifiable lvalue

Question

i have the following code:

#define NULL ((void*)0)
void* Globalptr = NULL;
void func(ptrtype* input)
{
 ((ptrtype*)Globalptr) = input;
}

I get Error on line ((ptrtype*)Globalptr) = input; says " expression must be a modifiable lvalue"

Answer 1

You must make the data to match the variable (lvalue), and not change the type of the variable to match the data:

Globalptr = (void*)input;

But since you can convert any data pointer to void* in C, you can simply do:

Globalptr = input;