Question

I am having problems with a void* to struct. My C++ code is as follows:

struct BUFF_TYPE {
    int a;
    int b;
};
typedef struct BUFF_TYPE BUFF_TYPE;

struct REG_TYPE {
    int c;
    void *buff;
};
typedef struct REG_TYPE REG_TYPE;

REG_TYPE regs[20];
const BUFF_TYPE b_A = {3,5};


void func_x() {
    int x,y;
    regs[4].buff = (BUFF_TYPE*)&b_A;
    x = regs[4].buff->a;
    y = regs[4].buff->b;
}

It gives me:

error: ‘void*’ is not a pointer-to-object type

in x and y assignments, could you please tell me how to access those a and b values?

BTW, I need the void* as sometimes I need to point to other kinds of buffers.

Answer 1

Before using ->, you must cast regs[4].buff to BUFF_TYPE*, so you need:

((BUFF_TYPE*) regs[4].buff)->a