skip--
			} else if n < len(dst) {
				dst[n] = retPC
				n++
			}
			return n < len(dst)
		}
	)

outer:
	for _, retPC := range pcBuf[1:] {
		callPC := retPC - 1
		fi := findfunc(callPC)
		if !fi.valid() {
			// There is no funcInfo if callPC belongs to a C function. In this case
			// we still keep the pc, but don't attempt to expand inlined frames.
			if more := skipOrAdd(retPC); !more {

}

// Contains reports whether v is present in s.
func Contains[E comparable](s []E, v E) bool {
	return slices.Contains(s, v)
}

// FindFunc finds the first element matching the function, or nil if none do
func FindFunc[E any](s []E, f func(E) bool) *E {
	idx := slices.IndexFunc(s, f)
	if idx == -1 {
		return nil
	}
	return &s[idx]
}

	// this to avoid write barriers.

	// Double-check m.
	if getg().m != h.mp {
		println("trap on wrong M", getg().m, h.mp)
		return false
	}
	f := findfunc(ctxt.sigpc())
	if !(stringslite.HasPrefix(funcname(f), "runtime.debugCall") || stringslite.HasPrefix(funcname(f), "debugCall")) {
		println("trap in unknown function", funcname(f))
		return false
	}

	for fidx, pc := range ancestor.pcs {
		f := findfunc(pc) // f previously validated
		if showfuncinfo(f.srcFunc(), fidx == 0, abi.FuncIDNormal) {
			printAncestorTracebackFuncInfo(f, pc)
		}
	}
	if len(ancestor.pcs) == tracebackInnerFrames {
		print("...additional frames elided...\n")
	}
	// Show what created goroutine, except main goroutine (goid 1).
	f := findfunc(ancestor.gopc)

			if markbuf[0] == 0 {
				markbuf[0] = ' '
			}
		}
		gwrite(markbuf[:])
		val := *(*uintptr)(unsafe.Pointer(p + i))
		print(hex(val))
		print(" ")

		// Can we symbolize val?
		fn := findfunc(val)
		if fn.valid() {
			print("<", funcname(fn), "+", hex(val-fn.entry()), "> ")
		}
	}
	minhexdigits = 0
	println()
	printunlock()

		// systemstack.)
		return debugCallSystemStack
	}

	// Switch to the system stack to avoid overflowing the user
	// stack.
	var ret string
	systemstack(func() {
		f := findfunc(pc)
		if !f.valid() {
			ret = debugCallUnknownFunc
			return
		}

		name := funcname(f)

		switch name {
		case "debugCall32",
			"debugCall64",
			"debugCall128",
			"debugCall256",

				return s == "b"
			},
			want: &elements[1],
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if got := FindFunc(tt.elements, tt.fn); !reflect.DeepEqual(got, tt.want) {
				t.Errorf("FindFunc got %v, want %v", got, tt.want)
			}
		})
	}
}

func TestFilter(t *testing.T) {
	tests := []struct {
		name     string
		elements []string

// with a nil pointer receiver.
//
// It is called from the generated wrapper code.
func panicwrap() {
	pc := getcallerpc()
	name := funcNameForPrint(funcname(findfunc(pc)))
	// name is something like "main.(*T).F".
	// We want to extract pkg ("main"), typ ("T"), and meth ("F").
	// Do it by finding the parens.
	i := bytealg.IndexByteString(name, '(')
	if i < 0 {

	// may try to read a stale LR that looks like a Go code
	// pointer and wander into the woods.
	if gp.m.incgo || findfunc(pc).valid() {
		// This wasn't a bad call, so use PC as sigpanic's
		// return PC.
		return true
	}
	if findfunc(lr).valid() {
		// This was a bad call, but the LR is good, so use the
		// LR as sigpanic's return PC.
		return false
	}

		// Update syscallsp, syscallpc in case traceback uses them.
		morebuf := thisg.m.morebuf
		gp.syscallsp = morebuf.sp
		gp.syscallpc = morebuf.pc
		pcname, pcoff := "(unknown)", uintptr(0)
		f := findfunc(gp.sched.pc)
		if f.valid() {
			pcname = funcname(f)
			pcoff = gp.sched.pc - f.entry()
		}
		print("runtime: newstack at ", pcname, "+", hex(pcoff),