test.c

#include <stdio.h>
#define BEGIN {
#define END   }
#define SOME_NUMBER 42

int main(int argc, char *argv[]) BEGIN
  printf("arg count is %i\n", argc);
  printf("some number is %i\n", SOME_NUMBER);
  return 0;
END

//FreeImage.h
#ifdef __cplusplus
#define FI_STRUCT(x) struct x
#define FI_ENUM(x)   enum x
#else
#define FI_STRUCT(x) typedef struct x x; struct x
#define FI_ENUM(x)   typedef int x; enum x
#endif

FI_ENUM(foo) { FOO_A = 0, FOO_B = 1, FOO_C = 3}
FI_STRUCT(bar) { int num; foo baz; }

test.expected.output.c

#include <stdio.h>
#define SOME_NUMBER 42

int main(int argc, char *argv[]) {
  printf("arg count is %i\n", argc);
  printf("some number is %i\n", SOME_NUMBER);
  return 0;
}

//FreeImage.h

typedef int foo; enum foo { FOO_A = 0, FOO_B = 1, FOO_C = 3}
typedef struct bar bar; struct bar { int num; foo baz; }