Embedded C: Can I pass members of a static struct to function in another file, IF a pointer to the member is passed by a fn in the same file

Question

I have a struct like this:

typedef struct {

   uint8_t var_1;
   uint8_t var_2;

}TYPE_struct_variables;

static TYPE_struct_variables variables;

For argument sake, I want to pass one of the members in this struct down another layer towards the metal. For this example, this is a data struct for an external device and I want to pass the member ' variables->var_1 ' / ' variables.var_1 ' to the usart interface of a host micro-controller. HOWEVER, I still want to restrict access to this struct for all functions outside this file. Would it work to send a pointer to this member if that pointer was sent by a fn in the same file as the struct?

Or would the program crash upon realizing it's a pointer inside a 'restricted' space?

Answer 1

C by itself doesn't know anything about restricted space in RAM. If you hide a variable as static it only won't get external linkage. That means it won't have a symbol outside of its compilation unit that you can reference to but it will have a regular address in the RAM or ROM (if you architecture supports that and the variable is constant) and that address is accessible for everybody.

Or in short: You can pass pointers to static variables in the same way as you can pass pointer to other variables or locations in RAM.