I have address of an struct store in int variable. Can I dereference the struct??

say: int x = 3432234; // memory address of struct now I want to access the some struct from it.

I have been suggest these steps.

1. store the address in an int variable
2. cast that int to a struct pointer
3. then dereference it

But don't know how to apply.

CodePudding user response：

It is very common to use structs this way in mare metal environments as hardware registers are often memory mapped.

typedef struct
{
    volatile uint32_t reg1;
    const volatile uint32_t reg2;
}PERIPH1__t;

#define PERIPH1ADDRESS  0x56664550UL

/* OR */
uintptr_t PERIPH1ADDRESS = 0x56664550UL;

#define PERIPH1 ((PERIPH1__t *)PERIPH1ADDRESS)


 /* somewhere in the code */
PERIPH1 -> reg1 = 34;
uint32_t reg2val = PERIPH1 -> reg2;

if you want to store the address in the integer variable, the best type will be uintptr_t which is guaranteed to accommodate any pointer.

int is signed and on many systems not large enough to store addresses - for example 64 bits systems often have 64 bits addresses and only 32bits integers.

CodePudding user response：

If you have a struct foo, the easy way is to not use an int x but make the type a pointer-to-struct foo, struct foo *x. One can use the arrow operator to access members from a valid pointer directly.

#include <stdio.h>

struct foo { int a, b; };

int main(void) {
    struct foo foo = { 1, 2 };
    struct foo *x = &foo;
    printf("%d, %d\n", x->a, x->b);
}

Sometimes, hardware requirements complicate this, but this is the simple solution.