Question

In C can a function expose memory that it ‘manageds’ at a lower level as readonly to those calling that function (exposing its address). return * const is not effective but I wondered if I was overlooking a programming tick?

Thanks.

const uint8_t * get_value(int index)  { static uint8_t data[2] = {0, 0}; return (const uint8_t *)&data[index]; }  int main(void) { uint8_t * value; value = get_value(1);  *value += 1; return 0; } 

@j_random_hacker Suggested a good compromise to my question that gives that extra barrier I’m looking for to prevent casual mis-use of that data.

typedef struct {     const uint8_t * value;     const uint8_t size;  } readonly_t;  readonly_t get_value(int index, int size)  {     static uint8_t data[2] = {0, 0};     uint8_t rsize;      /* ... validate index, size params */      readonly_t r = { &data[index], rsize };     return r; } 

Answer 1

It’s C! You can’t 🙂 There is always a way to circumvent it. Just make it const and hope somebody will not change it.

If you are hosting an add-in or something, you should run it in a separate process to limit its access to memory.