if gp.m.libcallsp != 0 {
		// We're in C code somewhere, traceback from the saved position.
		traceback1(gp.m.libcallpc, gp.m.libcallsp, 0, gp.m.libcallg.ptr(), 0)
		return
	}
	traceback1(pc, sp, lr, gp, unwindTrap)
}

func traceback1(pc, sp, lr uintptr, gp *g, flags unwindFlags) {
	// If the goroutine is in cgo, and we have a cgo traceback, print that.

// bits are the traceback value (0 off, 1 on, 2 include system).
const (
	tracebackCrash = 1 << iota
	tracebackAll
	tracebackShift = iota
)

var traceback_cache uint32 = 2 << tracebackShift
var traceback_env uint32

// gotraceback returns the current traceback settings.
//
// If level is 0, suppress all tracebacks.
// If level is 1, show tracebacks, but exclude runtime frames.

	// Cause the crash report to be written to stdout.
	panic("oops")
}

// TestTracebackSystem tests that the syntax of crash reports produced
// by GOTRACEBACK=system (see traceback2) contains a complete,
// parseable list of program counters for the running goroutine that
// can be parsed and fed to runtime.CallersFrames to obtain accurate
// information about the logical call stack, even in the presence of

## Runtime {#runtime}

The traceback printed by the runtime after an unhandled panic or other
fatal error now indents the second and subsequent lines of the error
message (for example, the argument to panic) by a single tab, so that
it can be unambiguously distinguished from the stack trace of the

	MOVD	LR, R10

	// We're coming from C code, initialize R0
	MOVD	$0, R0

	// If no traceback function, do usual sigtramp.
	MOVD	runtime·cgoTraceback(SB), R6
	CMP	$0, R6
	BEQ	sigtramp

	// If no traceback support function, which means that
	// runtime/cgo was not linked in, do usual sigtramp.
	MOVD	_cgo_callers(SB), R6
	CMP	$0, R6
	BEQ	sigtramp

	// To save m->curg->sched.pc, we push it onto the stack.
	// This has the added benefit that it looks to the traceback
	// routine like cgocallbackg is going to return to that
	// PC (because the frame we allocate below has the same
	// size as cgocallback_gofunc's frame declared above)
	// so that the traceback will seamlessly trace back into
	// the earlier calls.
	MOVV	m_curg(R12), g
	JAL	runtime·save_g(SB)

		systemstack(func() {
			g0 := getg()
			// Force traceback=1 to override GOTRACEBACK setting,
			// so that Stack's results are consistent.
			// GOTRACEBACK is only about crash dumps.
			g0.m.traceback = 1
			g0.writebuf = buf[0:0:len(buf)]
			goroutineheader(gp)
			traceback(pc, sp, 0, gp)
			if all {
				tracebackothers(gp)
			}
			g0.m.traceback = 0
			n = len(g0.writebuf)
			g0.writebuf = nil

	MOVW	m_curg(R1), g
	JAL	runtime·save_g(SB)
	MOVW	(g_sched+gobuf_sp)(g), R29
	MOVW	R0, (g_sched+gobuf_sp)(g)
	RET

noswitch:
	// already on m stack, just call directly
	// Using a tail call here cleans up tracebacks since we won't stop
	// at an intermediate systemstack.
	MOVW	0(REGCTXT), R4	// code pointer
	MOVW	0(R29), R31	// restore LR
	ADD	$4, R29
	JMP	(R4)

// func switchToCrashStack0(fn func())

				for _, line := range loc.Line {
					fns = append(fns, fmt.Sprintf("%s:%d", line.Function.Name, line.Line))
					leaf = line.Function.Name
				}
			}
			// runtime.sigprof synthesizes call stacks when "normal traceback is
			// impossible or has failed", using particular placeholder functions
			// to represent common failure cases. Look for those functions in
			// the leaf position as a sign that the call stack and its

	}

	// Check functions in the traceback.
	fns := []string{"main.pt1.func1", "panic", "main.pt2.func1", "panic", "main.pt2", "main.pt1"}
	for _, fn := range fns {
		re := regexp.MustCompile(`(?m)^` + regexp.QuoteMeta(fn) + `\(.*\n`)
		idx := re.FindStringIndex(output)
		if idx == nil {
			t.Fatalf("expected %q function in traceback:\n%s", fn, output)
		}
		output = output[idx[1]:]
	}
}