# go env -w checks validity of GOEXPERIMENT
env GOEXPERIMENT=
! go env -w GOEXPERIMENT=badexp
stderr 'unknown GOEXPERIMENT badexp'
go env -w GOEXPERIMENT=fieldtrack

# go env -w and go env -u work on unknown fields already in the go/env file
cp bad.env $GOENV
go env GOENV
cat $GOENV
go env
! stdout UNKNOWN
go env UNKNOWN
stdout yes
go env -w UNKNOWN=maybe

	mapinitnoop   loader.Sym
}

func (d *deadcodePass) init() {
	d.ldr.InitReachable()
	d.ifaceMethod = make(map[methodsig]bool)
	d.genericIfaceMethod = make(map[string]bool)
	if buildcfg.Experiment.FieldTrack {
		d.ldr.Reachparent = make([]loader.Sym, d.ldr.NSym())
	}
	d.dynlink = d.ctxt.DynlinkingGo()

	if d.ctxt.BuildMode == BuildModeShared {
		// Mark all symbols defined in this library as reachable when

	} else if target.HeadType == objabi.Hwindows {
		// already taken care of
	} else {
		ldr.Errorf(s, "adddynsym: unsupported binary format")
	}
}

func fieldtrack(arch *sys.Arch, l *loader.Loader) {
	var buf strings.Builder
	for i := loader.Sym(1); i < loader.Sym(l.NSym()); i++ {
		if name := l.SymName(i); strings.HasPrefix(name, "go:track.") {
			if l.AttrReachable(i) {

	// function. The root scope (0) has no parent, so the i'th
	// scope's parent is stored at Parents[i-1].
	Parents []ScopeID

	// Marks records scope boundary changes.
	Marks []Mark

	FieldTrack map[*obj.LSym]struct{}
	DebugInfo  interface{}
	LSym       *obj.LSym // Linker object in this function's native ABI (Func.ABI)

	Inl *Inline

	// RangeParent, if non-nil, is the first non-range body function containing

		// Not set. Use default.
	default:
		log.Fatalf("GO19CONCURRENTCOMPILATION must be 0, 1, or unset, got %q", e)
	}

	// TODO: Test and delete these conditions.
	if cfg.ExperimentErr != nil || cfg.Experiment.FieldTrack || cfg.Experiment.PreemptibleLoops {
		canDashC = false
	}

	if !canDashC {
		return 1
	}

	// Decide how many concurrent backend compilations to allow.
	//