Getting the value of uint8_t pointer

Question

Trying to understand someone else's code. Two questions, it is redundant to cast pdata as uint8_t? And how to do I see the value of pdata?

void *pb; 
uint8_t *pdata  = NULL;

//re-cast pb as uint8_t type
pdata = (uint8_t*)pb; // now pdata is equal to a uint8_t of whatever pb is, pb is an empty pointer
pdata += 1000;
printf("%d\n", pdata[0]);

That `printf` already outputs the value pointed to by `pdata`. Is that not what you want to see? — mkrieger1, May 21 '20 at 20:47
The cast is indeed redundant. C allows converting between data pointers and `void*` without casting. — Barmar, May 21 '20 at 20:48
Do you want to see the value of the pointer, or the value that it points to? Did you ever initialize `pb`? — Barmar, May 21 '20 at 20:49
Instead of `pdata += 1000`, you could just print `pdata[1000]` — Barmar, May 21 '20 at 20:50
Does this answer your question? [Why type cast a void pointer?](https://stackoverflow.com/questions/16986214/why-type-cast-a-void-pointer) — mkrieger1, May 21 '20 at 20:51
Also [Correct format specifier to print pointer or address?](https://stackoverflow.com/questions/9053658/correct-format-specifier-to-print-pointer-or-address) — mkrieger1, May 21 '20 at 20:52
And https://stackoverflow.com/questions/21887169/is-there-a-difference-between-using-ai-and-a-i — mkrieger1, May 21 '20 at 20:56

score 1 · Answer 1 · answered May 21 '20 at 21:14

Two questions, it is redundant to cast pdata as uint8_t?

Yes? The only uint8_t* case in your code is from pd pointer with is a void* pointer. A void* pointer can be implicitly converted to pointer to another type. pdata is a pointer to uint8_t, so casting it as uint8_t* pointer would be redundant. Casting pdata as uint8_t like (uint8_t)pdata would yield an implementation defined value.

And how to do I see the value of pdata?

It's typical to cast a pointer to void* and then use %p printf format specifier to print the value of a pointer. Most environments I worked with just print the value of the pointer in hex then.

printf("%p\n", (void*)pdata);

score 0 · Answer 2 · answered May 21 '20 at 21:21

Abstracting from the case when the author of the code does not know what he/she is doing such a cast (which in C is redundant) can be seen in:

The MISRA or another industrial standards compliant code (otherwise code analysers will cry)
Code which is likely to be compiled by the C++ compiler (yes I know it should not happen, but in real life someone can take your code and complain ...)

Getting the value of uint8_t pointer

2 Answers2