runtime/coverage: remove uses of //go:linkname

Move code to internal/coverage/cfile, making it possible to
access directly from testing/internal/testdeps, so that we can
avoid needing //go:linkname hacks.

For #67401.

Change-Id: I10b23a9970164afd2165e718ef3b2d9e86783883
Reviewed-on: https://go-review.googlesource.com/c/go/+/585820
Auto-Submit: Russ Cox <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>

src/cmd/go/internal/load/test.go

@@ -902,9 +902,6 @@ package main
 
 import (
 	"os"
-{{if .Cover}}
-	_ "unsafe"
-{{end}}
 {{if .TestMain}}
 	"reflect"
 {{end}}
@@ -944,45 +941,14 @@ var examples = []testing.InternalExample{
 }
 
 func init() {
-	testdeps.ImportPath = {{.ImportPath | printf "%q"}}
-}
-
 {{if .Cover}}
-
-//go:linkname runtime_coverage_processCoverTestDir runtime/coverage.processCoverTestDir
-func runtime_coverage_processCoverTestDir(dir string, cfile string, cmode string, cpkgs string) error
-
-//go:linkname testing_registerCover2 testing.registerCover2
-func testing_registerCover2(mode string, tearDown func(coverprofile string, gocoverdir string) (string, error), snapcov func() float64)
-
-//go:linkname runtime_coverage_markProfileEmitted runtime/coverage.markProfileEmitted
-func runtime_coverage_markProfileEmitted(val bool)
-
-//go:linkname runtime_coverage_snapshot runtime/coverage.snapshot
-func runtime_coverage_snapshot() float64
-
-func coverTearDown(coverprofile string, gocoverdir string) (string, error) {
-	var err error
-	if gocoverdir == "" {
-		gocoverdir, err = os.MkdirTemp("", "gocoverdir")
-		if err != nil {
-			return "error setting GOCOVERDIR: bad os.MkdirTemp return", err
-		}
-		defer os.RemoveAll(gocoverdir)
-	}
-	runtime_coverage_markProfileEmitted(true)
-	cmode := {{printf "%q" .Cover.Mode}}
-	if err := runtime_coverage_processCoverTestDir(gocoverdir, coverprofile, cmode, {{printf "%q" .Covered}}); err != nil {
-		return "error generating coverage report", err
-	}
-	return "", nil
-}
+	testdeps.CoverMode = {{printf "%q" .Cover.Mode}}
+	testdeps.Covered = {{printf "%q" .Covered}}
 {{end}}
+	testdeps.ImportPath = {{.ImportPath | printf "%q"}}
+}
 
 func main() {
-{{if .Cover}}
-	testing_registerCover2({{printf "%q" .Cover.Mode}}, coverTearDown, runtime_coverage_snapshot)
-{{end}}
 	m := testing.MainStart(testdeps.TestDeps{}, tests, benchmarks, fuzzTargets, examples)
 {{with .TestMain}}
 	{{.Package}}.{{.Name}}(m)

src/go/build/deps_test.go

@@ -608,9 +608,6 @@ var depsRules = `
 	internal/godebug, math/rand, encoding/hex, crypto/sha256
 	< internal/fuzz;
 
-	internal/fuzz, internal/testlog, runtime/pprof, regexp
-	< testing/internal/testdeps;
-
 	OS, flag, testing, internal/cfg, internal/platform, internal/goroot
 	< internal/testenv;
 
@@ -691,8 +688,12 @@ var depsRules = `
 	internal/coverage/decodecounter, internal/coverage/decodemeta,
 	internal/coverage/encodecounter, internal/coverage/encodemeta,
 	internal/coverage/pods
+	< internal/coverage/cfile
 	< runtime/coverage;
 
+	internal/coverage/cfile, internal/fuzz, internal/testlog, runtime/pprof, regexp
+	< testing/internal/testdeps;
+
 	# Test-only packages can have anything they want
 	CGO, internal/syscall/unix < net/internal/cgotest;
 

src/runtime/coverage/apis.go → src/internal/coverage/cfile/apis.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package coverage
+package cfile
 
 import (
 	"fmt"
@@ -12,24 +12,15 @@ import (
 	"unsafe"
 )
 
-// WriteMetaDir writes a coverage meta-data file for the currently
-// running program to the directory specified in 'dir'. An error will
-// be returned if the operation can't be completed successfully (for
-// example, if the currently running program was not built with
-// "-cover", or if the directory does not exist).
+// WriteMetaDir implements [runtime/coverage.WriteMetaDir].
 func WriteMetaDir(dir string) error {
 	if !finalHashComputed {
 		return fmt.Errorf("error: no meta-data available (binary not built with -cover?)")
 	}
 	return emitMetaDataToDirectory(dir, getCovMetaList())
 }
 
-// WriteMeta writes the meta-data content (the payload that would
-// normally be emitted to a meta-data file) for the currently running
-// program to the writer 'w'. An error will be returned if the
-// operation can't be completed successfully (for example, if the
-// currently running program was not built with "-cover", or if a
-// write fails).
+// WriteMeta implements [runtime/coverage.WriteMeta].
 func WriteMeta(w io.Writer) error {
 	if w == nil {
 		return fmt.Errorf("error: nil writer in WriteMeta")
@@ -41,26 +32,15 @@ func WriteMeta(w io.Writer) error {
 	return writeMetaData(w, ml, cmode, cgran, finalHash)
 }
 
-// WriteCountersDir writes a coverage counter-data file for the
-// currently running program to the directory specified in 'dir'. An
-// error will be returned if the operation can't be completed
-// successfully (for example, if the currently running program was not
-// built with "-cover", or if the directory does not exist). The
-// counter data written will be a snapshot taken at the point of the
-// call.
+// WriteCountersDir implements [runtime/coverage.WriteCountersDir].
 func WriteCountersDir(dir string) error {
 	if cmode != coverage.CtrModeAtomic {
 		return fmt.Errorf("WriteCountersDir invoked for program built with -covermode=%s (please use -covermode=atomic)", cmode.String())
 	}
 	return emitCounterDataToDirectory(dir)
 }
 
-// WriteCounters writes coverage counter-data content for the
-// currently running program to the writer 'w'. An error will be
-// returned if the operation can't be completed successfully (for
-// example, if the currently running program was not built with
-// "-cover", or if a write fails). The counter data written will be a
-// snapshot taken at the point of the invocation.
+// WriteCounters implements [runtime/coverage.WriteCounters].
 func WriteCounters(w io.Writer) error {
 	if w == nil {
 		return fmt.Errorf("error: nil writer in WriteCounters")
@@ -85,12 +65,7 @@ func WriteCounters(w io.Writer) error {
 	return s.emitCounterDataToWriter(w)
 }
 
-// ClearCounters clears/resets all coverage counter variables in the
-// currently running program. It returns an error if the program in
-// question was not built with the "-cover" flag. Clearing of coverage
-// counters is also not supported for programs not using atomic
-// counter mode (see more detailed comments below for the rationale
-// here).
+// ClearCounters implements [runtime/coverage.ClearCounters].
 func ClearCounters() error {
 	cl := getCovCounterList()
 	if len(cl) == 0 {

src/runtime/coverage/emit.go → src/internal/coverage/cfile/emit.go

@@ -2,7 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package coverage
+// Package cfile implements management of coverage files.
+// It provides functionality exported in runtime/coverage as well as
+// additional functionality used directly by package testing
+// through testing/internal/testdeps.
+package cfile
 
 import (
 	"crypto/md5"
@@ -28,17 +32,20 @@ import (
 // getCovMetaList returns a list of meta-data blobs registered
 // for the currently executing instrumented program. It is defined in the
 // runtime.
+//go:linkname getCovMetaList
 func getCovMetaList() []rtcov.CovMetaBlob
 
 // getCovCounterList returns a list of counter-data blobs registered
 // for the currently executing instrumented program. It is defined in the
 // runtime.
+//go:linkname getCovCounterList
 func getCovCounterList() []rtcov.CovCounterBlob
 
 // getCovPkgMap returns a map storing the remapped package IDs for
 // hard-coded runtime packages (see internal/coverage/pkgid.go for
 // more on why hard-coded package IDs are needed). This function
 // is defined in the runtime.
+//go:linkname getCovPkgMap
 func getCovPkgMap() map[int]int
 
 // emitState holds useful state information during the emit process.
@@ -574,16 +581,12 @@ func (s *emitState) emitCounterDataFile(finalHash [16]byte, w io.Writer) error {
 	return nil
 }
 
-// markProfileEmitted is injected to testmain via linkname.
-//go:linkname markProfileEmitted
-
-// markProfileEmitted signals the runtime/coverage machinery that
+// MarkProfileEmitted signals the coverage machinery that
 // coverage data output files have already been written out, and there
 // is no need to take any additional action at exit time. This
-// function is called (via linknamed reference) from the
-// coverage-related boilerplate code in _testmain.go emitted for go
-// unit tests.
-func markProfileEmitted(val bool) {
+// function is called from the coverage-related boilerplate code in _testmain.go
+// emitted for go unit tests.
+func MarkProfileEmitted(val bool) {
 	covProfileAlreadyEmitted = val
 }
 

src/runtime/coverage/emitdata_test.go → src/internal/coverage/cfile/emitdata_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package coverage
+package cfile
 
 import (
 	"fmt"
@@ -484,7 +484,7 @@ func TestIssue56006EmitDataRaceCoverRunningGoroutine(t *testing.T) {
 	cmd.Dir = filepath.Join("testdata", "issue56006")
 	b, err := cmd.CombinedOutput()
 	if err != nil {
-		t.Fatalf("go test -cover -race failed: %v", err)
+		t.Fatalf("go test -cover -race failed: %v\n%s", err, b)
 	}
 
 	// Don't want to see any data races in output.
@@ -510,7 +510,7 @@ func TestIssue59563TruncatedCoverPkgAll(t *testing.T) {
 	cmd.Dir = filepath.Join("testdata", "issue59563")
 	b, err := cmd.CombinedOutput()
 	if err != nil {
-		t.Fatalf("go test -cover failed: %v", err)
+		t.Fatalf("go test -cover failed: %v\n%s", err, b)
 	}
 
 	cmd = exec.Command(testenv.GoToolPath(t), "tool", "cover", "-func="+ppath)
@@ -530,7 +530,7 @@ func TestIssue59563TruncatedCoverPkgAll(t *testing.T) {
 		// We're only interested in the specific function "large" for
 		// the testcase being built. See the #59563 for details on why
 		// size matters.
-		if !(strings.HasPrefix(f[0], "runtime/coverage/testdata/issue59563/repro.go") && strings.Contains(line, "large")) {
+		if !(strings.HasPrefix(f[0], "internal/coverage/cfile/testdata/issue59563/repro.go") && strings.Contains(line, "large")) {
 			continue
 		}
 		nfound++

src/runtime/coverage/hooks.go → src/internal/coverage/cfile/hooks.go

@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package coverage
+package cfile
 
 import _ "unsafe"
 
-// initHook is invoked from the main package "init" routine in
+// InitHook is invoked from the main package "init" routine in
 // programs built with "-cover". This function is intended to be
-// called only by the compiler.
+// called only by the compiler (via runtime/coverage.initHook).
 //
 // If 'istest' is false, it indicates we're building a regular program
 // ("go build -cover ..."), in which case we immediately try to write
@@ -20,12 +20,12 @@ import _ "unsafe"
 // emitCounterData as exit hooks. In the normal case (e.g. regular "go
 // test -cover" run) the testmain.go boilerplate will run at the end
 // of the test, write out the coverage percentage, and then invoke
-// markProfileEmitted() to indicate that no more work needs to be
+// MarkProfileEmitted to indicate that no more work needs to be
 // done. If however that call is never made, this is a sign that the
 // test binary is being used as a replacement binary for the tool
 // being tested, hence we do want to run exit hooks when the program
 // terminates.
-func initHook(istest bool) {
+func InitHook(istest bool) {
 	// Note: hooks are run in reverse registration order, so
 	// register the counter data hook before the meta-data hook
 	// (in the case where two hooks are needed).

src/runtime/coverage/testsupport.go → src/internal/coverage/cfile/testsupport.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package coverage
+package cfile
 
 import (
 	"encoding/json"
@@ -22,20 +22,11 @@ import (
 	"unsafe"
 )
 
-// processCoverTestDir is injected in testmain.
-//go:linkname processCoverTestDir
-
-// processCoverTestDir is called (via a linknamed reference) from
+// ProcessCoverTestDir is called from
 // testmain code when "go test -cover" is in effect. It is not
 // intended to be used other than internally by the Go command's
 // generated code.
-func processCoverTestDir(dir string, cfile string, cm string, cpkg string) error {
-	return processCoverTestDirInternal(dir, cfile, cm, cpkg, os.Stdout)
-}
-
-// processCoverTestDirInternal is an io.Writer version of processCoverTestDir,
-// exposed for unit testing.
-func processCoverTestDirInternal(dir string, cfile string, cm string, cpkg string, w io.Writer) error {
+func ProcessCoverTestDir(dir string, cfile string, cm string, cpkg string, w io.Writer) error {
 	cmode := coverage.ParseCounterMode(cm)
 	if cmode == coverage.CtrModeInvalid {
 		return fmt.Errorf("invalid counter mode %q", cm)
@@ -280,16 +271,13 @@ func (ts *tstate) readAuxMetaFiles(metafiles string, importpaths map[string]stru
 	return nil
 }
 
-// snapshot is injected in testmain.
-//go:linkname snapshot
-
-// snapshot returns a snapshot of coverage percentage at a moment of
+// Snapshot returns a snapshot of coverage percentage at a moment of
 // time within a running test, so as to support the testing.Coverage()
 // function. This version doesn't examine coverage meta-data, so the
 // result it returns will be less accurate (more "slop") due to the
 // fact that we don't look at the meta data to see how many statements
 // are associated with each counter.
-func snapshot() float64 {
+func Snapshot() float64 {
 	cl := getCovCounterList()
 	if len(cl) == 0 {
 		// no work to do here.

src/runtime/coverage/ts_test.go → src/internal/coverage/cfile/ts_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package coverage
+package cfile
 
 import (
 	"encoding/json"
@@ -29,7 +29,7 @@ func testGoCoverDir(t *testing.T) string {
 }
 
 // TestTestSupport does a basic verification of the functionality in
-// runtime/coverage.processCoverTestDir (doing this here as opposed to
+// ProcessCoverTestDir (doing this here as opposed to
 // relying on other test paths will provide a better signal when
 // running "go test -cover" for this package).
 func TestTestSupport(t *testing.T) {
@@ -45,7 +45,7 @@ func TestTestSupport(t *testing.T) {
 
 	textfile := filepath.Join(t.TempDir(), "file.txt")
 	var sb strings.Builder
-	err := processCoverTestDirInternal(tgcd, textfile,
+	err := ProcessCoverTestDir(tgcd, textfile,
 		testing.CoverMode(), "", &sb)
 	if err != nil {
 		t.Fatalf("bad: %v", err)
@@ -91,9 +91,9 @@ func thisFunctionOnlyCalledFromSnapshotTest(n int) int {
 // coverage is not enabled, the hook is designed to just return
 // zero.
 func TestCoverageSnapshot(t *testing.T) {
-	C1 := snapshot()
+	C1 := Snapshot()
 	thisFunctionOnlyCalledFromSnapshotTest(15)
-	C2 := snapshot()
+	C2 := Snapshot()
 	cond := "C1 > C2"
 	val := C1 > C2
 	if testing.CoverMode() != "" {
@@ -185,7 +185,7 @@ func TestAuxMetaDataFiles(t *testing.T) {
 	// Kick off guts of test.
 	var sb strings.Builder
 	textfile := filepath.Join(td, "file2.txt")
-	err = processCoverTestDirInternal(tgcd, textfile,
+	err = ProcessCoverTestDir(tgcd, textfile,
 		testing.CoverMode(), "", &sb)
 	if err != nil {
 		t.Fatalf("bad: %v", err)