misc/cgo/testso{,var}: fix tests in module mode

Add _test.go files in the individal directories to invoke 'go build'
with appropriate arguments.

Move the test driver out of cmd/dist so that it's easier to invoke the
test separately (using 'go test .').

Updates #30228
Updates #28387

Change-Id: Ibc4a024a52c12a274058298b41cc90709f7f56c8
Reviewed-on: https://go-review.googlesource.com/c/163420
Reviewed-by: Ian Lance Taylor <iant@golang.org>

16 files changed, 436 insertions, 98 deletions

diff --git a/misc/cgo/testso/noso_test.go b/misc/cgo/testso/noso_test.go
new file mode 100644
index 0000000000..c88aebfb02
--- /dev/null
+++ b/misc/cgo/testso/noso_test.go
@@ -0,0 +1,9 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !cgo
+
+package so_test
+
+// Nothing to test.
diff --git a/misc/cgo/testso/overlaydir_test.go b/misc/cgo/testso/overlaydir_test.go
new file mode 100644
index 0000000000..10c874d925
--- /dev/null
+++ b/misc/cgo/testso/overlaydir_test.go
@@ -0,0 +1,81 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package so_test
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// overlayDir makes a minimal-overhead copy of srcRoot in which new files may be added.
+//
+// TODO: Once we no longer need to support the misc module in GOPATH mode,
+// factor this function out into a package to reduce duplication.
+func overlayDir(dstRoot, srcRoot string) error {
+	dstRoot = filepath.Clean(dstRoot)
+	if err := os.MkdirAll(dstRoot, 0777); err != nil {
+		return err
+	}
+
+	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	if err != nil {
+		symBase, err = filepath.Abs(srcRoot)
+		if err != nil {
+			return err
+		}
+	}
+
+	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
+		if err != nil || srcPath == srcRoot {
+			return err
+		}
+
+		suffix := strings.TrimPrefix(srcPath, srcRoot)
+		for len(suffix) > 0 && suffix[0] == filepath.Separator {
+			suffix = suffix[1:]
+		}
+		dstPath := filepath.Join(dstRoot, suffix)
+
+		perm := info.Mode() & os.ModePerm
+		if info.Mode()&os.ModeSymlink != 0 {
+			info, err = os.Stat(srcPath)
+			if err != nil {
+				return err
+			}
+			perm = info.Mode() & os.ModePerm
+		}
+
+		// Always copy directories (don't symlink them).
+		// If we add a file in the overlay, we don't want to add it in the original.
+		if info.IsDir() {
+			return os.Mkdir(dstPath, perm)
+		}
+
+		// If the OS supports symlinks, use them instead of copying bytes.
+		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+			return nil
+		}
+
+		// Otherwise, copy the bytes.
+		src, err := os.Open(srcPath)
+		if err != nil {
+			return err
+		}
+		defer src.Close()
+
+		dst, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
+		if err != nil {
+			return err
+		}
+
+		_, err = io.Copy(dst, src)
+		if closeErr := dst.Close(); err == nil {
+			err = closeErr
+		}
+		return err
+	})
+}
diff --git a/misc/cgo/testso/so_test.go b/misc/cgo/testso/so_test.go
new file mode 100644
index 0000000000..500b08fae8
--- /dev/null
+++ b/misc/cgo/testso/so_test.go
@@ -0,0 +1,126 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo
+
+package so_test
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func requireTestSOSupported(t *testing.T) {
+	t.Helper()
+	switch runtime.GOARCH {
+	case "arm", "arm64":
+		if runtime.GOOS == "darwin" {
+			t.Skip("No exec facility on iOS.")
+		}
+	case "ppc64":
+		t.Skip("External linking not implemented on ppc64 (issue #8912).")
+	case "mips64le", "mips64":
+		t.Skip("External linking not implemented on mips64.")
+	}
+	if runtime.GOOS == "android" {
+		t.Skip("No exec facility on Android.")
+	}
+}
+
+func TestSO(t *testing.T) {
+	requireTestSOSupported(t)
+
+	GOPATH, err := ioutil.TempDir("", "cgosotest")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.RemoveAll(GOPATH)
+
+	modRoot := filepath.Join(GOPATH, "src", "cgosotest")
+	if err := overlayDir(modRoot, "testdata"); err != nil {
+		log.Panic(err)
+	}
+	if err := ioutil.WriteFile(filepath.Join(modRoot, "go.mod"), []byte("module cgosotest\n"), 0666); err != nil {
+		log.Panic(err)
+	}
+
+	cmd := exec.Command("go", "env", "CC", "GOGCCFLAGS")
+	cmd.Dir = modRoot
+	cmd.Stderr = new(strings.Builder)
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	out, err := cmd.Output()
+	if err != nil {
+		t.Fatalf("%s: %v\n%s", strings.Join(cmd.Args, " "), err, cmd.Stderr)
+	}
+	lines := strings.Split(string(out), "\n")
+	if len(lines) != 3 || lines[2] != "" {
+		t.Fatalf("Unexpected output from %s:\n%s", strings.Join(cmd.Args, " "), lines)
+	}
+
+	cc := lines[0]
+	if cc == "" {
+		t.Fatal("CC environment variable (go env CC) cannot be empty")
+	}
+	gogccflags := strings.Split(lines[1], " ")
+
+	// build shared object
+	ext := "so"
+	args := append(gogccflags, "-shared")
+	switch runtime.GOOS {
+	case "darwin":
+		ext = "dylib"
+		args = append(args, "-undefined", "suppress", "-flat_namespace")
+	case "windows":
+		ext = "dll"
+		args = append(args, "-DEXPORT_DLL")
+	}
+	sofname := "libcgosotest." + ext
+	args = append(args, "-o", sofname, "cgoso_c.c")
+
+	cmd = exec.Command(cc, args...)
+	cmd.Dir = modRoot
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%s: %s\n%s", strings.Join(cmd.Args, " "), err, out)
+	}
+	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
+
+	cmd = exec.Command("go", "build", "-o", "main.exe", "main.go")
+	cmd.Dir = modRoot
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%s: %s\n%s", strings.Join(cmd.Args, " "), err, out)
+	}
+	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
+
+	cmd = exec.Command("./main.exe")
+	cmd.Dir = modRoot
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	if runtime.GOOS != "windows" {
+		s := "LD_LIBRARY_PATH"
+		if runtime.GOOS == "darwin" {
+			s = "DYLD_LIBRARY_PATH"
+		}
+		cmd.Env = append(os.Environ(), s+"=.")
+
+		// On FreeBSD 64-bit architectures, the 32-bit linker looks for
+		// different environment variables.
+		if runtime.GOOS == "freebsd" && runtime.GOARCH == "386" {
+			cmd.Env = append(cmd.Env, "LD_32_LIBRARY_PATH=.")
+		}
+	}
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%s: %s\n%s", strings.Join(cmd.Args, " "), err, out)
+	}
+	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
+}
diff --git a/misc/cgo/testso/cgoso.c b/misc/cgo/testso/testdata/cgoso.c
index 917f472d36..917f472d36 100644
--- a/misc/cgo/testso/cgoso.c
+++ b/misc/cgo/testso/testdata/cgoso.c
diff --git a/misc/cgo/testso/cgoso.go b/misc/cgo/testso/testdata/cgoso.go
index 29814fa43a..29814fa43a 100644
--- a/misc/cgo/testso/cgoso.go
+++ b/misc/cgo/testso/testdata/cgoso.go
diff --git a/misc/cgo/testso/cgoso_c.c b/misc/cgo/testso/testdata/cgoso_c.c
index 7a38022b54..7a38022b54 100644
--- a/misc/cgo/testso/cgoso_c.c
+++ b/misc/cgo/testso/testdata/cgoso_c.c
diff --git a/misc/cgo/testso/cgoso_unix.go b/misc/cgo/testso/testdata/cgoso_unix.go
index 49cdeaa2f5..49cdeaa2f5 100644
--- a/misc/cgo/testso/cgoso_unix.go
+++ b/misc/cgo/testso/testdata/cgoso_unix.go
diff --git a/misc/cgo/testso/main.go b/misc/cgo/testso/testdata/main.go
index 88aa4322d2..963d45121e 100644
--- a/misc/cgo/testso/main.go
+++ b/misc/cgo/testso/testdata/main.go
@@ -6,7 +6,7 @@
 
 package main
 
-import "."
+import "cgosotest"
 
 func main() {
 	cgosotest.Test()
diff --git a/misc/cgo/testsovar/noso_test.go b/misc/cgo/testsovar/noso_test.go
new file mode 100644
index 0000000000..c88aebfb02
--- /dev/null
+++ b/misc/cgo/testsovar/noso_test.go
@@ -0,0 +1,9 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !cgo
+
+package so_test
+
+// Nothing to test.
diff --git a/misc/cgo/testsovar/overlaydir_test.go b/misc/cgo/testsovar/overlaydir_test.go
new file mode 100644
index 0000000000..10c874d925
--- /dev/null
+++ b/misc/cgo/testsovar/overlaydir_test.go
@@ -0,0 +1,81 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package so_test
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// overlayDir makes a minimal-overhead copy of srcRoot in which new files may be added.
+//
+// TODO: Once we no longer need to support the misc module in GOPATH mode,
+// factor this function out into a package to reduce duplication.
+func overlayDir(dstRoot, srcRoot string) error {
+	dstRoot = filepath.Clean(dstRoot)
+	if err := os.MkdirAll(dstRoot, 0777); err != nil {
+		return err
+	}
+
+	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	if err != nil {
+		symBase, err = filepath.Abs(srcRoot)
+		if err != nil {
+			return err
+		}
+	}
+
+	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
+		if err != nil || srcPath == srcRoot {
+			return err
+		}
+
+		suffix := strings.TrimPrefix(srcPath, srcRoot)
+		for len(suffix) > 0 && suffix[0] == filepath.Separator {
+			suffix = suffix[1:]
+		}
+		dstPath := filepath.Join(dstRoot, suffix)
+
+		perm := info.Mode() & os.ModePerm
+		if info.Mode()&os.ModeSymlink != 0 {
+			info, err = os.Stat(srcPath)
+			if err != nil {
+				return err
+			}
+			perm = info.Mode() & os.ModePerm
+		}
+
+		// Always copy directories (don't symlink them).
+		// If we add a file in the overlay, we don't want to add it in the original.
+		if info.IsDir() {
+			return os.Mkdir(dstPath, perm)
+		}
+
+		// If the OS supports symlinks, use them instead of copying bytes.
+		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+			return nil
+		}
+
+		// Otherwise, copy the bytes.
+		src, err := os.Open(srcPath)
+		if err != nil {
+			return err
+		}
+		defer src.Close()
+
+		dst, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
+		if err != nil {
+			return err
+		}
+
+		_, err = io.Copy(dst, src)
+		if closeErr := dst.Close(); err == nil {
+			err = closeErr
+		}
+		return err
+	})
+}
diff --git a/misc/cgo/testsovar/so_test.go b/misc/cgo/testsovar/so_test.go
new file mode 100644
index 0000000000..500b08fae8
--- /dev/null
+++ b/misc/cgo/testsovar/so_test.go
@@ -0,0 +1,126 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo
+
+package so_test
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func requireTestSOSupported(t *testing.T) {
+	t.Helper()
+	switch runtime.GOARCH {
+	case "arm", "arm64":
+		if runtime.GOOS == "darwin" {
+			t.Skip("No exec facility on iOS.")
+		}
+	case "ppc64":
+		t.Skip("External linking not implemented on ppc64 (issue #8912).")
+	case "mips64le", "mips64":
+		t.Skip("External linking not implemented on mips64.")
+	}
+	if runtime.GOOS == "android" {
+		t.Skip("No exec facility on Android.")
+	}
+}
+
+func TestSO(t *testing.T) {
+	requireTestSOSupported(t)
+
+	GOPATH, err := ioutil.TempDir("", "cgosotest")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer os.RemoveAll(GOPATH)
+
+	modRoot := filepath.Join(GOPATH, "src", "cgosotest")
+	if err := overlayDir(modRoot, "testdata"); err != nil {
+		log.Panic(err)
+	}
+	if err := ioutil.WriteFile(filepath.Join(modRoot, "go.mod"), []byte("module cgosotest\n"), 0666); err != nil {
+		log.Panic(err)
+	}
+
+	cmd := exec.Command("go", "env", "CC", "GOGCCFLAGS")
+	cmd.Dir = modRoot
+	cmd.Stderr = new(strings.Builder)
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	out, err := cmd.Output()
+	if err != nil {
+		t.Fatalf("%s: %v\n%s", strings.Join(cmd.Args, " "), err, cmd.Stderr)
+	}
+	lines := strings.Split(string(out), "\n")
+	if len(lines) != 3 || lines[2] != "" {
+		t.Fatalf("Unexpected output from %s:\n%s", strings.Join(cmd.Args, " "), lines)
+	}
+
+	cc := lines[0]
+	if cc == "" {
+		t.Fatal("CC environment variable (go env CC) cannot be empty")
+	}
+	gogccflags := strings.Split(lines[1], " ")
+
+	// build shared object
+	ext := "so"
+	args := append(gogccflags, "-shared")
+	switch runtime.GOOS {
+	case "darwin":
+		ext = "dylib"
+		args = append(args, "-undefined", "suppress", "-flat_namespace")
+	case "windows":
+		ext = "dll"
+		args = append(args, "-DEXPORT_DLL")
+	}
+	sofname := "libcgosotest." + ext
+	args = append(args, "-o", sofname, "cgoso_c.c")
+
+	cmd = exec.Command(cc, args...)
+	cmd.Dir = modRoot
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%s: %s\n%s", strings.Join(cmd.Args, " "), err, out)
+	}
+	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
+
+	cmd = exec.Command("go", "build", "-o", "main.exe", "main.go")
+	cmd.Dir = modRoot
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%s: %s\n%s", strings.Join(cmd.Args, " "), err, out)
+	}
+	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
+
+	cmd = exec.Command("./main.exe")
+	cmd.Dir = modRoot
+	cmd.Env = append(os.Environ(), "GOPATH="+GOPATH)
+	if runtime.GOOS != "windows" {
+		s := "LD_LIBRARY_PATH"
+		if runtime.GOOS == "darwin" {
+			s = "DYLD_LIBRARY_PATH"
+		}
+		cmd.Env = append(os.Environ(), s+"=.")
+
+		// On FreeBSD 64-bit architectures, the 32-bit linker looks for
+		// different environment variables.
+		if runtime.GOOS == "freebsd" && runtime.GOARCH == "386" {
+			cmd.Env = append(cmd.Env, "LD_32_LIBRARY_PATH=.")
+		}
+	}
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("%s: %s\n%s", strings.Join(cmd.Args, " "), err, out)
+	}
+	t.Logf("%s:\n%s", strings.Join(cmd.Args, " "), out)
+}
diff --git a/misc/cgo/testsovar/cgoso.go b/misc/cgo/testsovar/testdata/cgoso.go
index 88d44c2c6e..88d44c2c6e 100644
--- a/misc/cgo/testsovar/cgoso.go
+++ b/misc/cgo/testsovar/testdata/cgoso.go
diff --git a/misc/cgo/testsovar/cgoso_c.c b/misc/cgo/testsovar/testdata/cgoso_c.c
index a448c01342..a448c01342 100644
--- a/misc/cgo/testsovar/cgoso_c.c
+++ b/misc/cgo/testsovar/testdata/cgoso_c.c
diff --git a/misc/cgo/testsovar/cgoso_c.h b/misc/cgo/testsovar/testdata/cgoso_c.h
index 640db7b396..640db7b396 100644
--- a/misc/cgo/testsovar/cgoso_c.h
+++ b/misc/cgo/testsovar/testdata/cgoso_c.h
diff --git a/misc/cgo/testsovar/main.go b/misc/cgo/testsovar/testdata/main.go
index 9c8a1c4e66..87b52cef60 100644
--- a/misc/cgo/testsovar/main.go
+++ b/misc/cgo/testsovar/testdata/main.go
@@ -6,7 +6,7 @@
 
 package main
 
-import "."
+import "cgosotest"
 
 func main() {
 	cgosotest.Test()
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index c5cc6dcb3c..31b44e8ef4 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -6,7 +6,6 @@ package main
 
 import (
 	"bytes"
-	"errors"
 	"flag"
 	"fmt"
 	"io/ioutil"
@@ -675,22 +674,8 @@ func (t *tester) registerTests() {
 	// recompile the entire standard library. If make.bash ran with
 	// special -gcflags, that's not true.
 	if t.cgoEnabled && gogcflags == "" {
-		if t.cgoTestSOSupported() {
-			t.tests = append(t.tests, distTest{
-				name:    "testso",
-				heading: "../misc/cgo/testso",
-				fn: func(dt *distTest) error {
-					return t.cgoTestSO(dt, "misc/cgo/testso")
-				},
-			})
-			t.tests = append(t.tests, distTest{
-				name:    "testsovar",
-				heading: "../misc/cgo/testsovar",
-				fn: func(dt *distTest) error {
-					return t.cgoTestSO(dt, "misc/cgo/testsovar")
-				},
-			})
-		}
+		t.registerHostTest("testso", "../misc/cgo/testso", "misc/cgo/testso", ".")
+		t.registerHostTest("testsovar", "../misc/cgo/testsovar", "misc/cgo/testsovar", ".")
 		if t.supportedBuildmode("c-archive") {
 			t.registerHostTest("testcarchive", "../misc/cgo/testcarchive", "misc/cgo/testcarchive", ".")
 		}
@@ -1166,85 +1151,6 @@ func (t *tester) runPending(nextTest *distTest) {
 	}
 }
 
-func (t *tester) cgoTestSOSupported() bool {
-	if goos == "android" || t.iOS() {
-		// No exec facility on Android or iOS.
-		return false
-	}
-	if goarch == "ppc64" {
-		// External linking not implemented on ppc64 (issue #8912).
-		return false
-	}
-	if goarch == "mips64le" || goarch == "mips64" {
-		// External linking not implemented on mips64.
-		return false
-	}
-	return true
-}
-
-func (t *tester) cgoTestSO(dt *distTest, testpath string) error {
-	t.runPending(dt)
-
-	timelog("start", dt.name)
-	defer timelog("end", dt.name)
-
-	dir := filepath.Join(goroot, testpath)
-
-	// build shared object
-	output, err := exec.Command("go", "env", "CC").Output()
-	if err != nil {
-		return fmt.Errorf("Error running go env CC: %v", err)
-	}
-	cc := strings.TrimSuffix(string(output), "\n")
-	if cc == "" {
-		return errors.New("CC environment variable (go env CC) cannot be empty")
-	}
-	output, err = exec.Command("go", "env", "GOGCCFLAGS").Output()
-	if err != nil {
-		return fmt.Errorf("Error running go env GOGCCFLAGS: %v", err)
-	}
-	gogccflags := strings.Split(strings.TrimSuffix(string(output), "\n"), " ")
-
-	ext := "so"
-	args := append(gogccflags, "-shared")
-	switch goos {
-	case "darwin":
-		ext = "dylib"
-		args = append(args, "-undefined", "suppress", "-flat_namespace")
-	case "windows":
-		ext = "dll"
-		args = append(args, "-DEXPORT_DLL")
-	}
-	sofname := "libcgosotest." + ext
-	args = append(args, "-o", sofname, "cgoso_c.c")
-
-	if err := t.dirCmd(dir, cc, args).Run(); err != nil {
-		return err
-	}
-	defer os.Remove(filepath.Join(dir, sofname))
-
-	if err := t.dirCmd(dir, "go", "build", "-o", "main.exe", "main.go").Run(); err != nil {
-		return err
-	}
-	defer os.Remove(filepath.Join(dir, "main.exe"))
-
-	cmd := t.dirCmd(dir, "./main.exe")
-	if goos != "windows" {
-		s := "LD_LIBRARY_PATH"
-		if goos == "darwin" {
-			s = "DYLD_LIBRARY_PATH"
-		}
-		cmd.Env = append(os.Environ(), s+"=.")
-
-		// On FreeBSD 64-bit architectures, the 32-bit linker looks for
-		// different environment variables.
-		if goos == "freebsd" && gohostarch == "386" {
-			cmd.Env = append(cmd.Env, "LD_32_LIBRARY_PATH=.")
-		}
-	}
-	return cmd.Run()
-}
-
 func (t *tester) hasBash() bool {
 	switch gohostos {
 	case "windows", "plan9":