I have a piece of embedded C software that requires multiple const pointers to const data. So far I've been repeating two lines of code to initialize them:
const int data = 0xF0; // const int
const int* const buffer = &data; // const pointer to const int
Previously I used lots of type casts, but found that too error prone while reviewed by teammates. I'm open to using them if I can find a way to use them clearly and consistently.
I also need to avoid discarding my const qualifier when passing to functions, as discarding this has actually caused one bug in development already.
You can define the pointer and the data in a single declaration (albeit not readable and not recommended:
const int data = 0xF0, * const buffer = &data;
Using C99 compound literals, you can also write:
const int * const buffer = (const int[]){ 0xF0 };
or
const int * const buffer = (const int[1]){ 0xF0 };
or
const int * const buffer = &(const int){ 0xF0 };
Note that the order of the const and int keywords does not matter and it may be more readable to put the const keyword closer to the * it qualifies:
int const * const buffer = (int const []) { 0xF0 };
The question is: Why do you need a pointer at all? If the pointer is constant, it cannot be changed to point to something else, hence why define a pointer when you can pass &data directly?
Removing the const qualifier for function calls is an indication of design flaws: a function taking a pointer to data that it does not modify should have the argument defined as whatevertype const *arg and you do not need any cast when passing the address of the data, be it const qualified or not. If the function does modify the data it gets a pointer to, passing it data that is defined as const will trigger undefined behavior upon modification as the data may be located in read only memory.