Is there any workaround for making a structure member somehow 'private' in C?

Question

I am developing a simple library in C, for my own + some friends personal use.

I am currently having a C structure with some members that should be somehow hidden fr

Answer 1

The usual techique is this:

/* foo.h */
typedef struct Foo Foo;

Foo *foo_create(...);

void foo_bark(Foo* foo, double loudness);

/* foo.c */
struct Foo {
  int private_var;
};

You can partially hide data members by defining Foo in the header and FooPrivate in the .c file thus:

struct FooPrivate {
  Foo public_stuff;
  int private_var;
}

But then your implementation has to cast back and forth between Foo and FooPrivate, which I find to be a royal PITA, and is a maintenance burden if you change your mind later and want to make something private. Unless you want suck every last CPU cycle out of the code, just use accessor functions.