// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"fmt"
	"runtime"
	"strings"
)

func init() {
	register("TracebackAncestors", TracebackAncestors)
}

const numGoroutines = 3
const numFrames = 2

func TracebackAncestors() {
	w := make(chan struct{})
	recurseThenCallGo(w, numGoroutines, numFrames, true)
	<-w
	printStack()
	close(w)
}

	{name: "traceallocfree", atomic: &debug.traceallocfree},
	{name: "tracecheckstackownership", value: &debug.traceCheckStackOwnership},
	{name: "tracebackancestors", value: &debug.tracebackancestors},
	{name: "tracefpunwindoff", value: &debug.tracefpunwindoff},
}

func parsedebugvars() {
	// defaults
	debug.cgocheck = 1
	debug.invalidptr = 1

func TestTracebackAncestors(t *testing.T) {
	goroutineRegex := regexp.MustCompile(`goroutine [0-9]+ \[`)
	for _, tracebackDepth := range []int{0, 1, 5, 50} {
		output := runTestProg(t, "testprog", "TracebackAncestors", fmt.Sprintf("GODEBUG=tracebackancestors=%d", tracebackDepth))

		numGoroutines := 3
		numFrames := 2
		ancestorsExpected := numGoroutines
		if numGoroutines > tracebackDepth {
			ancestorsExpected = tracebackDepth
		}

	processors, threads and goroutines.

	schedtrace: setting schedtrace=X causes the scheduler to emit a single line to standard
	error every X milliseconds, summarizing the scheduler state.

	tracebackancestors: setting tracebackancestors=N extends tracebacks with the stacks at
	which goroutines were created, where N limits the number of ancestor goroutines to
	report. This also extends the information returned by runtime.Stack.

	gopc          uintptr         // pc of go statement that created this goroutine
	ancestors     *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
	startpc       uintptr         // pc of goroutine function
	racectx       uintptr
	waiting       *sudog         // sudog structures this g is waiting on (that have a valid elem ptr); in lock order

	// Copy all prior info, except for the root goroutine (goid 0).
	if debug.tracebackancestors <= 0 || callergp.goid == 0 {
		return nil
	}
	var callerAncestors []ancestorInfo
	if callergp.ancestors != nil {
		callerAncestors = *callergp.ancestors
	}
	n := int32(len(callerAncestors)) + 1
	if n > debug.tracebackancestors {
		n = debug.tracebackancestors
	}
	ancestors := make([]ancestorInfo, n)