func (f matchStringOnly) StartCPUProfile(w io.Writer) error           { return errMain }
func (f matchStringOnly) StopCPUProfile()                             {}
func (f matchStringOnly) WriteProfileTo(string, io.Writer, int) error { return errMain }
func (f matchStringOnly) ImportPath() string                          { return "" }
func (f matchStringOnly) StartTestLog(io.Writer)                      {}

func (t test) expectFail() bool {
	failureSets := []map[string]bool{types2Failures}

	// Note: gccgo supports more 32-bit architectures than this, but
	// hopefully the 32-bit failures are fixed before this matters.
	switch goarch {
	case "386", "arm", "mips", "mipsle":
		failureSets = append(failureSets, types2Failures32Bit)
	}

	testName := path.Join(t.dir, t.goFile) // Test name is '/'-separated.

	// goal, and subtract out everything else. This is of course impossible; the definition
	// is circular! However, this impossible definition contains a key insight: the amount
	// we're *going* to use matters just as much as whatever we're currently using.
	//
	// Consider if the heap shrinks to 1/10th its size, leaving behind lots of free and
	// unscavenged memory. mappedReady - heapAlloc will be quite large, because of that free

	// Compute the size of the frame again. FP and SP have
	// completely different values here than they did above,
	// but only their difference matters.
	LEAQ	fn+0(FP), AX
	SUBQ	SP, AX

	// Restore g->sched (== m->curg->sched) from saved values.
	get_tls(CX)
	MOVQ	g(CX), SI
	MOVQ	SP, DI
	ADDQ	AX, DI
	MOVQ	-8(DI), BX

	tg.run("install", "p1")
	tg.wantNotStale("p1", "", "./testgo list claims p1 is stale, incorrectly, before any changes")

	// Changing mtime of runtime/internal/sys/sys.go
	// should have no effect: only the content matters.
	// In fact this should be true even outside a release branch.
	sys := tg.path("goroot/src/runtime/internal/sys/sys.go")
	tg.sleep()
	restore := addVar(sys, 0)
	restore()

	return nil
}

// extld returns the current external linker.
func (ctxt *Link) extld() []string {
	if len(flagExtld) == 0 {
		// Return the default external linker for the platform.
		// This only matters when link tool is called directly without explicit -extld,
		// go tool already passes the correct linker in other cases.
		switch buildcfg.GOOS {
		case "darwin", "freebsd", "openbsd":
			flagExtld = []string{"clang"}