typedef struct Tos Tos;typedef struct Plink Plink; #pragma incomplete Plink struct Tos {	struct			/* Per process profiling */	{		Plink	*pp;	/* known to be 0(ptr) */		Plink	*next;	/* known to be 4(ptr) */		Plink	*last;		Plink	*first;		ulong	pid;		ulong	what;	} prof;	uvlong	cyclefreq;	/* cycle clock frequency if there is one, 0 otherwise */	vlong	kcycles;	/* cycles spent in kernel */	vlong	pcycles;	/* cycles spent in process (kernel + user) */	ulong	pid;		/* might as well put the pid here */	ulong	clock;	uint	machno;		/* mp->machno */	/* top of stack is here */}; extern Tos *_tos;