declare_file_struct.h

#if 0 /* example use: */

#define EMIT_FIXUP_DEFINITIONS 1
/* if EMIT_FIXUP_DEFINITIONS is 0 or undefined then
 * only the struct declaration will be emitted
 * typically you want to only emit fixup function
 * definitions in a single translation unit.
 */

#define DECLARE_STRUCT_NAME BITMAPFILEHEADER
#define DECLARE_STRUCT_COMPONENTS \
    STRUCT_FIELD(u16le, bfType) \
    STRUCT_FIELD(u32le, bfSize) \
    STRUCT_FIELD(pad16, bfReserved1) \
    STRUCT_FIELD(pad16, bfReserved2) \
    STRUCT_FIELD(u32le, bfOffBits)
#include "declare_file_struct.h"
#undef DECLARE_STRUCT_NAME
#undef DECLARE_STRUCT_COMPONENTS

#endif /* end example */

#ifndef DECLARE_STRUCT_NAME
#error "declare_file_struct.h requires DECLARE_STRUCT_NAME to be defined first"
#endif
#ifndef DECLARE_STRUCT_COMPONENTS
#error "declare_file_struct.h requires DECLARE_STRUCT_COMPONENTS to be defined first"
#endif

#ifdef STRUCT_FIELD
#error "declare_file_struct.h requires STRUCT_FIELD to be undefined"
#endif

#ifndef IDENT_JOIN
#define IDENT_JOIN2(x,y) x ## y
#define IDENT_JOIN(x,y) IDENT_JOIN2(x,y)
#endif

struct DECLARE_STRUCT_NAME {
#define STRUCT_FIELD(type, field) type field;
	DECLARE_STRUCT_COMPONENTS
#undef STRUCT_FIELD
} __attribute__((__packed__));

#if defined(EMIT_FIXUP_DEFINITIONS) && EMIT_FIXUP_DEFINITIONS

void IDENT_JOIN(fixup_, DECLARE_STRUCT_NAME)(struct DECLARE_STRUCT_NAME *obj) {
#define STRUCT_FIELD(type, field) fixup_ ## type (&obj->field);
	DECLARE_STRUCT_COMPONENTS
#undef STRUCT_FIELD
}

#endif /* EMIT_FIXUP_DEFINITIONS */