将结构体类型转换为int

Question

Hello every one I want to ask a question about type casting.It confuses me two much. I am writing a code in which I am using an already created function having prototype like this.

void function (uint8_t * output , const uint_8 * buffer , int bufferlen);

it is called like this

const char * text = "some text";
uint8_t result[16];
function (result, (uint8_t *)text , strlen(text)); 

But my problem is that I have to call the same and pass it a struct so I call the function like this

const struct mystruct * ms;

function (result, (uint8_t *)ms , sizeof(*ms)); 

But it giving me segmentation fault. can any one guide me what should I pass in place of third argument.

Thanks

I ma using C programming linux

Answer 1

How big is the Struct? Your result has a particular length, 16, I'm guessing that the function your are calling is copying into result. If it's too small you have a problem.

Answer 2

You declared an uninitialized pointer that does not point at valid memory. That is why the function crashes when it tries to use that pointer. Use this instead:

struct mystruct *ms = (struct mystruct *) malloc(sizeof(struct mystruct)); 
function (result, (uint8_t *)ms, sizeof(struct mystruct));  
free(ms);

Or:

struct mystruct ms; 
function (result, (uint8_t *)&ms, sizeof(ms));