Hiding members in a C struct

Question

I\'ve been reading about OOP in C but I never liked how you can\'t have private data members like you can in C++. But then it came to my mind that you could create 2 structu

Answer 1

Related, though not exactly hiding.

Is to conditionally deprecate members.

Note that this works for GCC/Clang, but MSVC and other compilers can deprecate too, so its possible to come up with a more portable version.

If you build with fairly strict warnings, or warnings as errors, this at least avoids accidental use.

// =========================================
// in somestruct.h

#ifdef _IS_SOMESTRUCT_C
#  if defined(__GNUC__)
#    define HIDE_MEMBER __attribute__((deprecated))
#  else
#    define HIDE_MEMBER  /* no hiding! */
#  endif
#else
#  define HIDE_MEMBER
#endif

typedef struct {
  int _public_member;
  int _private_member  HIDE_MEMBER;
} SomeStruct;

#undef HIDE_MEMBER


// =========================================
// in somestruct.c
#define _IS_SOMESTRUCT_C
#include "somestruct.h"

SomeStruct *SomeStruct_Create()
{
  SomeStructSource *p = (SomeStructSource *)malloc(sizeof(SomeStructSource));
  p->_private_member = 42;
  return (SomeStruct *)p;
}