DTRACE_USTACK_NFRAMES
uint32_t depth = DTRACE_USTACK_NFRAMES(arg);
if ((nframes = DTRACE_USTACK_NFRAMES(arg)) == 0)
(nframes = DTRACE_USTACK_NFRAMES(arg)) == 0) {
int nframes = DTRACE_USTACK_NFRAMES(arg);
int depth = DTRACE_USTACK_NFRAMES(
int depth = DTRACE_USTACK_NFRAMES(
DTRACE_USTACK_NFRAMES(rec->dtrd_arg) + 1);