// coresound.h#include <allegro.h>#include <logg.h>#define SP_NORMAL 0#define SP_ONEVOICE 1#define NUMVOICES 256struct obj_t;typedef struct{ obj_t* object; // ERROR: syntax error before "obj_t" int playmode;} voice_t;extern voice_t* voicelist[NUMVOICES];extern LOGG_Stream *oggsong;// object.h...#include <allegro.h>#include "r_actors.h"...typedef struct{ unsigned short int sprite; // Index of sprite to be drawn at object's position unsigned char drawstyle; // Manner in which to draw the sprite int x; // X Position int y; // Y Position int momx; // X momentum int momy; // Y momentum int type; // Dictates object's identity and behavior ...}obj_t;...extern obj_t objectlist[MAXOBJS];...