return 0
	}

	ctxt := u.g.ptr().cgoCtxt[u.cgoCtxt]
	u.cgoCtxt--
	cgoContextPCs(ctxt, pcBuf)
	for i, pc := range pcBuf {
		if pc == 0 {
			return i
		}
	}
	return len(pcBuf)
}

// tracebackPCs populates pcBuf with the return addresses for each frame from u
// and returns the number of PCs written to pcBuf. The returned PCs correspond
// to "logical frames" rather than "physical frames"; that is if A is inlined

	// pcbuf which is usually given to us by our caller. When it's not, we have
	// to allocate one here. This will only happen for goroutines that were in a
	// syscall when the goroutine profile started or for goroutines that manage
	// to execute before we finish iterating over all the goroutines.
	if pcbuf == nil {
		pcbuf = makeProfStack()
	}

	var u unwinder