//go:linkname setMaxStack runtime/debug.setMaxStack
func setMaxStack(in int) (out int) {
	out = int(maxstacksize)
	maxstacksize = uintptr(in)
	return out
}

//go:linkname setPanicOnFault runtime/debug.setPanicOnFault
func setPanicOnFault(new bool) (old bool) {
	gp := getg()
	old = gp.paniconfault
	gp.paniconfault = new
	return old

	if err != nil {
		t.Fatalf("can't map anonymous memory: %s", err)
	}
	defer syscall.Munmap(m)
	old := debug.SetPanicOnFault(true)
	defer debug.SetPanicOnFault(old)
	const lowBits = 0x3e7
	defer func() {
		r := recover()
		if r == nil {
			t.Fatalf("write did not fault")
		}
		type addressable interface {
			Addr() uintptr
		}

// may depend on the platform.
// SetPanicOnFault applies only to the current goroutine.
// It returns the previous setting.
func SetPanicOnFault(enabled bool) bool {
	return setPanicOnFault(enabled)
}

// WriteHeapDump writes a description of the heap and the objects in
// it to the given file descriptor.
//
// WriteHeapDump suspends the execution of all goroutines until the heap

package debug

import (
	"time"
)

// Implemented in package runtime.
func readGCStats(*[]time.Duration)
func freeOSMemory()
func setMaxStack(int) int
func setGCPercent(int32) int32
func setPanicOnFault(bool) bool
func setMaxThreads(int) int

	{_SigPanic, "sys: fp:"},                // SIGFLOAT

	// All other traps are normally handled as if they were marked SigThrow.
	// We mark them SigPanic here so that debug.SetPanicOnFault will work.
	{_SigPanic, "sys: trap:"}, // SIGTRAP

	// Writes to a closed pipe can be handled if desired, otherwise they're ignored.
	{_SigNotify, "sys: write on closed pipe"},

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

package main

import (
	"encoding/binary"
	"runtime"
	"runtime/debug"
	"unsafe"
)

func main() {
	debug.SetPanicOnFault(true)
	defer func() {
		if err := recover(); err == nil {
			panic("not panicking")
		}
		pc, _, _, _ := runtime.Caller(10)
		f := runtime.FuncForPC(pc)
		if f == nil || f.Name() != "main.f" {
			if f == nil {

	SetCPUProfileRate(0)
}

// Addresses to test for faulting behavior.
// This is less a test of SetPanicOnFault and more a check that
// the operating system and the runtime can process these faults
// correctly. That is, we're indirectly testing that without SetPanicOnFault
// these would manage to turn into ordinary crashes.
// Note that these are truncated on 32-bit systems, so the bottom 32 bits

		dst[i] = src[i]
		n++
	}
	return
}

func main() {
	// Turn the eventual fault into a panic, not a program crash,
	// so that memcopy can recover.
	debug.SetPanicOnFault(true)

	size := syscall.Getpagesize()

	// Map 16 pages of data with a 4-page hole in the middle.
	data, err := syscall.Mmap(-1, 0, 16*size, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANON|syscall.MAP_PRIVATE)

	// we don't suppress panics that could have been produced from other sources.
	type addrer interface {
		Addr() uintptr
	}

	debug.SetPanicOnFault(old)

	if e := recover(); e != nil {
		if _, ok := e.(addrer); ok || e == errCorrupt {
			// This panic was almost certainly caused by SetPanicOnFault or our panic(errCorrupt).
			err := fmt.Errorf("error reading module index: %v", e)
			if errp != nil {
				*errp = err
				return

// The address provided is best-effort.
// The veracity of the result may depend on the platform.
// Errors providing this method will only be returned as
// a result of using [runtime/debug.SetPanicOnFault].
func (e errorAddressString) Addr() uintptr {
	return e.addr
}

// plainError represents a runtime error described a string without
// the prefix "runtime error: " after invoking errorString.Error().