Adding upstream version 1.18.10.upstream/1.18.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 856 insertions, 0 deletions

diff --git a/misc/cgo/testcshared/cshared_test.go b/misc/cgo/testcshared/cshared_test.go
new file mode 100644
index 0000000..1cd8c2a
--- /dev/null
+++ b/misc/cgo/testcshared/cshared_test.go
@@ -0,0 +1,856 @@
+// Copyright 2017 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 cshared_test
+
+import (
+	"bytes"
+	"debug/elf"
+	"debug/pe"
+	"encoding/binary"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+	"unicode"
+)
+
+// C compiler with args (from $(go env CC) $(go env GOGCCFLAGS)).
+var cc []string
+
+// ".exe" on Windows.
+var exeSuffix string
+
+var GOOS, GOARCH, GOROOT string
+var installdir, androiddir string
+var libSuffix, libgoname string
+
+func TestMain(m *testing.M) {
+	os.Exit(testMain(m))
+}
+
+func testMain(m *testing.M) int {
+	log.SetFlags(log.Lshortfile)
+	flag.Parse()
+	if testing.Short() && os.Getenv("GO_BUILDER_NAME") == "" {
+		fmt.Printf("SKIP - short mode and $GO_BUILDER_NAME not set\n")
+		os.Exit(0)
+	}
+
+	GOOS = goEnv("GOOS")
+	GOARCH = goEnv("GOARCH")
+	GOROOT = goEnv("GOROOT")
+
+	if _, err := os.Stat(GOROOT); os.IsNotExist(err) {
+		log.Fatalf("Unable able to find GOROOT at '%s'", GOROOT)
+	}
+
+	androiddir = fmt.Sprintf("/data/local/tmp/testcshared-%d", os.Getpid())
+	if runtime.GOOS != GOOS && GOOS == "android" {
+		args := append(adbCmd(), "exec-out", "mkdir", "-p", androiddir)
+		cmd := exec.Command(args[0], args[1:]...)
+		out, err := cmd.CombinedOutput()
+		if err != nil {
+			log.Fatalf("setupAndroid failed: %v\n%s\n", err, out)
+		}
+		defer cleanupAndroid()
+	}
+
+	cc = []string{goEnv("CC")}
+
+	out := goEnv("GOGCCFLAGS")
+	quote := '\000'
+	start := 0
+	lastSpace := true
+	backslash := false
+	s := string(out)
+	for i, c := range s {
+		if quote == '\000' && unicode.IsSpace(c) {
+			if !lastSpace {
+				cc = append(cc, s[start:i])
+				lastSpace = true
+			}
+		} else {
+			if lastSpace {
+				start = i
+				lastSpace = false
+			}
+			if quote == '\000' && !backslash && (c == '"' || c == '\'') {
+				quote = c
+				backslash = false
+			} else if !backslash && quote == c {
+				quote = '\000'
+			} else if (quote == '\000' || quote == '"') && !backslash && c == '\\' {
+				backslash = true
+			} else {
+				backslash = false
+			}
+		}
+	}
+	if !lastSpace {
+		cc = append(cc, s[start:])
+	}
+
+	switch GOOS {
+	case "darwin", "ios":
+		// For Darwin/ARM.
+		// TODO(crawshaw): can we do better?
+		cc = append(cc, []string{"-framework", "CoreFoundation", "-framework", "Foundation"}...)
+	case "android":
+		cc = append(cc, "-pie")
+	}
+	libgodir := GOOS + "_" + GOARCH
+	switch GOOS {
+	case "darwin", "ios":
+		if GOARCH == "arm64" {
+			libgodir += "_shared"
+		}
+	case "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "solaris", "illumos":
+		libgodir += "_shared"
+	}
+	cc = append(cc, "-I", filepath.Join("pkg", libgodir))
+
+	// Force reallocation (and avoid aliasing bugs) for parallel tests that append to cc.
+	cc = cc[:len(cc):len(cc)]
+
+	if GOOS == "windows" {
+		exeSuffix = ".exe"
+	}
+
+	// Copy testdata into GOPATH/src/testcshared, along with a go.mod file
+	// declaring the same path.
+
+	GOPATH, err := os.MkdirTemp("", "cshared_test")
+	if err != nil {
+		log.Panic(err)
+	}
+	defer os.RemoveAll(GOPATH)
+	os.Setenv("GOPATH", GOPATH)
+
+	modRoot := filepath.Join(GOPATH, "src", "testcshared")
+	if err := overlayDir(modRoot, "testdata"); err != nil {
+		log.Panic(err)
+	}
+	if err := os.Chdir(modRoot); err != nil {
+		log.Panic(err)
+	}
+	os.Setenv("PWD", modRoot)
+	if err := os.WriteFile("go.mod", []byte("module testcshared\n"), 0666); err != nil {
+		log.Panic(err)
+	}
+
+	// Directory where cgo headers and outputs will be installed.
+	// The installation directory format varies depending on the platform.
+	output, err := exec.Command("go", "list",
+		"-buildmode=c-shared",
+		"-installsuffix", "testcshared",
+		"-f", "{{.Target}}",
+		"./libgo").CombinedOutput()
+	if err != nil {
+		log.Panicf("go list failed: %v\n%s", err, output)
+	}
+	target := string(bytes.TrimSpace(output))
+	libgoname = filepath.Base(target)
+	installdir = filepath.Dir(target)
+	libSuffix = strings.TrimPrefix(filepath.Ext(target), ".")
+
+	return m.Run()
+}
+
+func goEnv(key string) string {
+	out, err := exec.Command("go", "env", key).Output()
+	if err != nil {
+		log.Printf("go env %s failed:\n%s", key, err)
+		log.Panicf("%s", err.(*exec.ExitError).Stderr)
+	}
+	return strings.TrimSpace(string(out))
+}
+
+func cmdToRun(name string) string {
+	return "./" + name + exeSuffix
+}
+
+func adbCmd() []string {
+	cmd := []string{"adb"}
+	if flags := os.Getenv("GOANDROID_ADB_FLAGS"); flags != "" {
+		cmd = append(cmd, strings.Split(flags, " ")...)
+	}
+	return cmd
+}
+
+func adbPush(t *testing.T, filename string) {
+	if runtime.GOOS == GOOS || GOOS != "android" {
+		return
+	}
+	args := append(adbCmd(), "push", filename, fmt.Sprintf("%s/%s", androiddir, filename))
+	cmd := exec.Command(args[0], args[1:]...)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("adb command failed: %v\n%s\n", err, out)
+	}
+}
+
+func adbRun(t *testing.T, env []string, adbargs ...string) string {
+	if GOOS != "android" {
+		t.Fatalf("trying to run adb command when operating system is not android.")
+	}
+	args := append(adbCmd(), "exec-out")
+	// Propagate LD_LIBRARY_PATH to the adb shell invocation.
+	for _, e := range env {
+		if strings.Contains(e, "LD_LIBRARY_PATH=") {
+			adbargs = append([]string{e}, adbargs...)
+			break
+		}
+	}
+	shellcmd := fmt.Sprintf("cd %s; %s", androiddir, strings.Join(adbargs, " "))
+	args = append(args, shellcmd)
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("adb command failed: %v\n%s\n", err, out)
+	}
+	return strings.Replace(string(out), "\r", "", -1)
+}
+
+func run(t *testing.T, extraEnv []string, args ...string) string {
+	t.Helper()
+	cmd := exec.Command(args[0], args[1:]...)
+	if len(extraEnv) > 0 {
+		cmd.Env = append(os.Environ(), extraEnv...)
+	}
+
+	if GOOS != "windows" {
+		// TestUnexportedSymbols relies on file descriptor 30
+		// being closed when the program starts, so enforce
+		// that in all cases. (The first three descriptors are
+		// stdin/stdout/stderr, so we just need to make sure
+		// that cmd.ExtraFiles[27] exists and is nil.)
+		cmd.ExtraFiles = make([]*os.File, 28)
+	}
+
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("command failed: %v\n%v\n%s\n", args, err, out)
+	} else {
+		t.Logf("run: %v", args)
+	}
+	return string(out)
+}
+
+func runExe(t *testing.T, extraEnv []string, args ...string) string {
+	t.Helper()
+	if runtime.GOOS != GOOS && GOOS == "android" {
+		return adbRun(t, append(os.Environ(), extraEnv...), args...)
+	}
+	return run(t, extraEnv, args...)
+}
+
+func runCC(t *testing.T, args ...string) string {
+	t.Helper()
+	// This function is run in parallel, so append to a copy of cc
+	// rather than cc itself.
+	return run(t, nil, append(append([]string(nil), cc...), args...)...)
+}
+
+func createHeaders() error {
+	// The 'cgo' command generates a number of additional artifacts,
+	// but we're only interested in the header.
+	// Shunt the rest of the outputs to a temporary directory.
+	objDir, err := os.MkdirTemp("", "testcshared_obj")
+	if err != nil {
+		return err
+	}
+	defer os.RemoveAll(objDir)
+
+	// Generate a C header file for p, which is a non-main dependency
+	// of main package libgo.
+	//
+	// TODO(golang.org/issue/35715): This should be simpler.
+	args := []string{"go", "tool", "cgo",
+		"-objdir", objDir,
+		"-exportheader", "p.h",
+		filepath.Join(".", "p", "p.go")}
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("command failed: %v\n%v\n%s\n", args, err, out)
+	}
+
+	// Generate a C header file for libgo itself.
+	args = []string{"go", "install", "-buildmode=c-shared",
+		"-installsuffix", "testcshared", "./libgo"}
+	cmd = exec.Command(args[0], args[1:]...)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("command failed: %v\n%v\n%s\n", args, err, out)
+	}
+
+	args = []string{"go", "build", "-buildmode=c-shared",
+		"-installsuffix", "testcshared",
+		"-o", libgoname,
+		filepath.Join(".", "libgo", "libgo.go")}
+	if GOOS == "windows" && strings.HasSuffix(args[6], ".a") {
+		args[6] = strings.TrimSuffix(args[6], ".a") + ".dll"
+	}
+	cmd = exec.Command(args[0], args[1:]...)
+	out, err = cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("command failed: %v\n%v\n%s\n", args, err, out)
+	}
+	if GOOS == "windows" {
+		// We can't simply pass -Wl,--out-implib, because this relies on having imports from multiple packages,
+		// which results in the linkers output implib getting overwritten at each step. So instead build the
+		// import library the traditional way, using a def file.
+		err = os.WriteFile("libgo.def",
+			[]byte("LIBRARY libgo.dll\nEXPORTS\n\tDidInitRun\n\tDidMainRun\n\tDivu\n\tFromPkg\n\t_cgo_dummy_export\n"),
+			0644)
+		if err != nil {
+			return fmt.Errorf("unable to write def file: %v", err)
+		}
+		out, err = exec.Command(cc[0], append(cc[1:], "-print-prog-name=dlltool")...).CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("unable to find dlltool path: %v\n%s\n", err, out)
+		}
+		dlltoolpath := strings.TrimSpace(string(out))
+		if filepath.Ext(dlltoolpath) == "" {
+			// Some compilers report slash-separated paths without extensions
+			// instead of ordinary Windows paths.
+			// Try to find the canonical name for the path.
+			if lp, err := exec.LookPath(dlltoolpath); err == nil {
+				dlltoolpath = lp
+			}
+		}
+
+		args := []string{dlltoolpath, "-D", args[6], "-l", libgoname, "-d", "libgo.def"}
+
+		if filepath.Ext(dlltoolpath) == "" {
+			// This is an unfortunate workaround for
+			// https://github.com/mstorsjo/llvm-mingw/issues/205 in which
+			// we basically reimplement the contents of the dlltool.sh
+			// wrapper: https://git.io/JZFlU.
+			// TODO(thanm): remove this workaround once we can upgrade
+			// the compilers on the windows-arm64 builder.
+			dlltoolContents, err := os.ReadFile(args[0])
+			if err != nil {
+				return fmt.Errorf("unable to read dlltool: %v\n", err)
+			}
+			if bytes.HasPrefix(dlltoolContents, []byte("#!/bin/sh")) && bytes.Contains(dlltoolContents, []byte("llvm-dlltool")) {
+				base, name := filepath.Split(args[0])
+				args[0] = filepath.Join(base, "llvm-dlltool")
+				var machine string
+				switch prefix, _, _ := strings.Cut(name, "-"); prefix {
+				case "i686":
+					machine = "i386"
+				case "x86_64":
+					machine = "i386:x86-64"
+				case "armv7":
+					machine = "arm"
+				case "aarch64":
+					machine = "arm64"
+				}
+				if len(machine) > 0 {
+					args = append(args, "-m", machine)
+				}
+			}
+		}
+
+		out, err = exec.Command(args[0], args[1:]...).CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("unable to run dlltool to create import library: %v\n%s\n", err, out)
+		}
+	}
+
+	if runtime.GOOS != GOOS && GOOS == "android" {
+		args = append(adbCmd(), "push", libgoname, fmt.Sprintf("%s/%s", androiddir, libgoname))
+		cmd = exec.Command(args[0], args[1:]...)
+		out, err = cmd.CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("adb command failed: %v\n%s\n", err, out)
+		}
+	}
+
+	return nil
+}
+
+var (
+	headersOnce sync.Once
+	headersErr  error
+)
+
+func createHeadersOnce(t *testing.T) {
+	headersOnce.Do(func() {
+		headersErr = createHeaders()
+	})
+	if headersErr != nil {
+		t.Fatal(headersErr)
+	}
+}
+
+func cleanupAndroid() {
+	if GOOS != "android" {
+		return
+	}
+	args := append(adbCmd(), "exec-out", "rm", "-rf", androiddir)
+	cmd := exec.Command(args[0], args[1:]...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		log.Panicf("cleanupAndroid failed: %v\n%s\n", err, out)
+	}
+}
+
+// test0: exported symbols in shared lib are accessible.
+func TestExportedSymbols(t *testing.T) {
+	t.Parallel()
+
+	cmd := "testp0"
+	bin := cmdToRun(cmd)
+
+	createHeadersOnce(t)
+
+	runCC(t, "-I", installdir, "-o", cmd, "main0.c", libgoname)
+	adbPush(t, cmd)
+
+	defer os.Remove(bin)
+
+	out := runExe(t, []string{"LD_LIBRARY_PATH=."}, bin)
+	if strings.TrimSpace(out) != "PASS" {
+		t.Error(out)
+	}
+}
+
+func checkNumberOfExportedFunctionsWindows(t *testing.T, exportAllSymbols bool) {
+	const prog = `
+package main
+
+import "C"
+
+//export GoFunc
+func GoFunc() {
+	println(42)
+}
+
+//export GoFunc2
+func GoFunc2() {
+	println(24)
+}
+
+func main() {
+}
+`
+
+	tmpdir := t.TempDir()
+
+	srcfile := filepath.Join(tmpdir, "test.go")
+	objfile := filepath.Join(tmpdir, "test.dll")
+	if err := os.WriteFile(srcfile, []byte(prog), 0666); err != nil {
+		t.Fatal(err)
+	}
+	argv := []string{"build", "-buildmode=c-shared"}
+	if exportAllSymbols {
+		argv = append(argv, "-ldflags", "-extldflags=-Wl,--export-all-symbols")
+	}
+	argv = append(argv, "-o", objfile, srcfile)
+	out, err := exec.Command("go", argv...).CombinedOutput()
+	if err != nil {
+		t.Fatalf("build failure: %s\n%s\n", err, string(out))
+	}
+
+	f, err := pe.Open(objfile)
+	if err != nil {
+		t.Fatalf("pe.Open failed: %v", err)
+	}
+	defer f.Close()
+	section := f.Section(".edata")
+	if section == nil {
+		t.Skip(".edata section is not present")
+	}
+
+	// TODO: deduplicate this struct from cmd/link/internal/ld/pe.go
+	type IMAGE_EXPORT_DIRECTORY struct {
+		_                 [2]uint32
+		_                 [2]uint16
+		_                 [2]uint32
+		NumberOfFunctions uint32
+		NumberOfNames     uint32
+		_                 [3]uint32
+	}
+	var e IMAGE_EXPORT_DIRECTORY
+	if err := binary.Read(section.Open(), binary.LittleEndian, &e); err != nil {
+		t.Fatalf("binary.Read failed: %v", err)
+	}
+
+	// Only the two exported functions and _cgo_dummy_export should be exported
+	expectedNumber := uint32(3)
+
+	if exportAllSymbols {
+		if e.NumberOfFunctions <= expectedNumber {
+			t.Fatalf("missing exported functions: %v", e.NumberOfFunctions)
+		}
+		if e.NumberOfNames <= expectedNumber {
+			t.Fatalf("missing exported names: %v", e.NumberOfNames)
+		}
+	} else {
+		if e.NumberOfFunctions != expectedNumber {
+			t.Fatalf("got %d exported functions; want %d", e.NumberOfFunctions, expectedNumber)
+		}
+		if e.NumberOfNames != expectedNumber {
+			t.Fatalf("got %d exported names; want %d", e.NumberOfNames, expectedNumber)
+		}
+	}
+}
+
+func TestNumberOfExportedFunctions(t *testing.T) {
+	if GOOS != "windows" {
+		t.Skip("skipping windows only test")
+	}
+	t.Parallel()
+
+	t.Run("OnlyExported", func(t *testing.T) {
+		checkNumberOfExportedFunctionsWindows(t, false)
+	})
+	t.Run("All", func(t *testing.T) {
+		checkNumberOfExportedFunctionsWindows(t, true)
+	})
+}
+
+// test1: shared library can be dynamically loaded and exported symbols are accessible.
+func TestExportedSymbolsWithDynamicLoad(t *testing.T) {
+	t.Parallel()
+
+	if GOOS == "windows" {
+		t.Logf("Skipping on %s", GOOS)
+		return
+	}
+
+	cmd := "testp1"
+	bin := cmdToRun(cmd)
+
+	createHeadersOnce(t)
+
+	if GOOS != "freebsd" {
+		runCC(t, "-o", cmd, "main1.c", "-ldl")
+	} else {
+		runCC(t, "-o", cmd, "main1.c")
+	}
+	adbPush(t, cmd)
+
+	defer os.Remove(bin)
+
+	out := runExe(t, nil, bin, "./"+libgoname)
+	if strings.TrimSpace(out) != "PASS" {
+		t.Error(out)
+	}
+}
+
+// test2: tests libgo2 which does not export any functions.
+func TestUnexportedSymbols(t *testing.T) {
+	t.Parallel()
+
+	if GOOS == "windows" {
+		t.Logf("Skipping on %s", GOOS)
+		return
+	}
+
+	cmd := "testp2"
+	bin := cmdToRun(cmd)
+	libname := "libgo2." + libSuffix
+
+	run(t,
+		nil,
+		"go", "build",
+		"-buildmode=c-shared",
+		"-installsuffix", "testcshared",
+		"-o", libname, "./libgo2",
+	)
+	adbPush(t, libname)
+
+	linkFlags := "-Wl,--no-as-needed"
+	if GOOS == "darwin" || GOOS == "ios" {
+		linkFlags = ""
+	}
+
+	runCC(t, "-o", cmd, "main2.c", linkFlags, libname)
+	adbPush(t, cmd)
+
+	defer os.Remove(libname)
+	defer os.Remove(bin)
+
+	out := runExe(t, []string{"LD_LIBRARY_PATH=."}, bin)
+
+	if strings.TrimSpace(out) != "PASS" {
+		t.Error(out)
+	}
+}
+
+// test3: tests main.main is exported on android.
+func TestMainExportedOnAndroid(t *testing.T) {
+	t.Parallel()
+
+	switch GOOS {
+	case "android":
+		break
+	default:
+		t.Logf("Skipping on %s", GOOS)
+		return
+	}
+
+	cmd := "testp3"
+	bin := cmdToRun(cmd)
+
+	createHeadersOnce(t)
+
+	runCC(t, "-o", cmd, "main3.c", "-ldl")
+	adbPush(t, cmd)
+
+	defer os.Remove(bin)
+
+	out := runExe(t, nil, bin, "./"+libgoname)
+	if strings.TrimSpace(out) != "PASS" {
+		t.Error(out)
+	}
+}
+
+func testSignalHandlers(t *testing.T, pkgname, cfile, cmd string) {
+	libname := pkgname + "." + libSuffix
+	run(t,
+		nil,
+		"go", "build",
+		"-buildmode=c-shared",
+		"-installsuffix", "testcshared",
+		"-o", libname, pkgname,
+	)
+	adbPush(t, libname)
+	if GOOS != "freebsd" {
+		runCC(t, "-pthread", "-o", cmd, cfile, "-ldl")
+	} else {
+		runCC(t, "-pthread", "-o", cmd, cfile)
+	}
+	adbPush(t, cmd)
+
+	bin := cmdToRun(cmd)
+
+	defer os.Remove(libname)
+	defer os.Remove(bin)
+	defer os.Remove(pkgname + ".h")
+
+	out := runExe(t, nil, bin, "./"+libname)
+	if strings.TrimSpace(out) != "PASS" {
+		t.Error(run(t, nil, bin, libname, "verbose"))
+	}
+}
+
+// test4: test signal handlers
+func TestSignalHandlers(t *testing.T) {
+	t.Parallel()
+	if GOOS == "windows" {
+		t.Logf("Skipping on %s", GOOS)
+		return
+	}
+	testSignalHandlers(t, "./libgo4", "main4.c", "testp4")
+}
+
+// test5: test signal handlers with os/signal.Notify
+func TestSignalHandlersWithNotify(t *testing.T) {
+	t.Parallel()
+	if GOOS == "windows" {
+		t.Logf("Skipping on %s", GOOS)
+		return
+	}
+	testSignalHandlers(t, "./libgo5", "main5.c", "testp5")
+}
+
+func TestPIE(t *testing.T) {
+	t.Parallel()
+
+	switch GOOS {
+	case "linux", "android":
+		break
+	default:
+		t.Logf("Skipping on %s", GOOS)
+		return
+	}
+
+	createHeadersOnce(t)
+
+	f, err := elf.Open(libgoname)
+	if err != nil {
+		t.Fatalf("elf.Open failed: %v", err)
+	}
+	defer f.Close()
+
+	ds := f.SectionByType(elf.SHT_DYNAMIC)
+	if ds == nil {
+		t.Fatalf("no SHT_DYNAMIC section")
+	}
+	d, err := ds.Data()
+	if err != nil {
+		t.Fatalf("can't read SHT_DYNAMIC contents: %v", err)
+	}
+	for len(d) > 0 {
+		var tag elf.DynTag
+		switch f.Class {
+		case elf.ELFCLASS32:
+			tag = elf.DynTag(f.ByteOrder.Uint32(d[:4]))
+			d = d[8:]
+		case elf.ELFCLASS64:
+			tag = elf.DynTag(f.ByteOrder.Uint64(d[:8]))
+			d = d[16:]
+		}
+		if tag == elf.DT_TEXTREL {
+			t.Fatalf("%s has DT_TEXTREL flag", libgoname)
+		}
+	}
+}
+
+// Test that installing a second time recreates the header file.
+func TestCachedInstall(t *testing.T) {
+	tmpdir, err := os.MkdirTemp("", "cshared")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	copyFile(t, filepath.Join(tmpdir, "src", "testcshared", "go.mod"), "go.mod")
+	copyFile(t, filepath.Join(tmpdir, "src", "testcshared", "libgo", "libgo.go"), filepath.Join("libgo", "libgo.go"))
+	copyFile(t, filepath.Join(tmpdir, "src", "testcshared", "p", "p.go"), filepath.Join("p", "p.go"))
+
+	env := append(os.Environ(), "GOPATH="+tmpdir, "GOBIN="+filepath.Join(tmpdir, "bin"))
+
+	buildcmd := []string{"go", "install", "-x", "-buildmode=c-shared", "-installsuffix", "testcshared", "./libgo"}
+
+	cmd := exec.Command(buildcmd[0], buildcmd[1:]...)
+	cmd.Dir = filepath.Join(tmpdir, "src", "testcshared")
+	cmd.Env = env
+	t.Log(buildcmd)
+	out, err := cmd.CombinedOutput()
+	t.Logf("%s", out)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var libgoh, ph string
+
+	walker := func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			t.Fatal(err)
+		}
+		var ps *string
+		switch filepath.Base(path) {
+		case "libgo.h":
+			ps = &libgoh
+		case "p.h":
+			ps = &ph
+		}
+		if ps != nil {
+			if *ps != "" {
+				t.Fatalf("%s found again", *ps)
+			}
+			*ps = path
+		}
+		return nil
+	}
+
+	if err := filepath.Walk(tmpdir, walker); err != nil {
+		t.Fatal(err)
+	}
+
+	if libgoh == "" {
+		t.Fatal("libgo.h not installed")
+	}
+
+	if err := os.Remove(libgoh); err != nil {
+		t.Fatal(err)
+	}
+
+	cmd = exec.Command(buildcmd[0], buildcmd[1:]...)
+	cmd.Dir = filepath.Join(tmpdir, "src", "testcshared")
+	cmd.Env = env
+	t.Log(buildcmd)
+	out, err = cmd.CombinedOutput()
+	t.Logf("%s", out)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := os.Stat(libgoh); err != nil {
+		t.Errorf("libgo.h not installed in second run: %v", err)
+	}
+}
+
+// copyFile copies src to dst.
+func copyFile(t *testing.T, dst, src string) {
+	t.Helper()
+	data, err := os.ReadFile(src)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(filepath.Dir(dst), 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(dst, data, 0666); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGo2C2Go(t *testing.T) {
+	switch GOOS {
+	case "darwin", "ios", "windows":
+		// Non-ELF shared libraries don't support the multiple
+		// copies of the runtime package implied by this test.
+		t.Skipf("linking c-shared into Go programs not supported on %s; issue 29061, 49457", GOOS)
+	case "android":
+		t.Skip("test fails on android; issue 29087")
+	}
+
+	t.Parallel()
+
+	tmpdir, err := os.MkdirTemp("", "cshared-TestGo2C2Go")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+
+	lib := filepath.Join(tmpdir, "libtestgo2c2go."+libSuffix)
+	var env []string
+	if GOOS == "windows" && strings.HasSuffix(lib, ".a") {
+		env = append(env, "CGO_LDFLAGS=-Wl,--out-implib,"+lib, "CGO_LDFLAGS_ALLOW=.*")
+		lib = strings.TrimSuffix(lib, ".a") + ".dll"
+	}
+	run(t, env, "go", "build", "-buildmode=c-shared", "-o", lib, "./go2c2go/go")
+
+	cgoCflags := os.Getenv("CGO_CFLAGS")
+	if cgoCflags != "" {
+		cgoCflags += " "
+	}
+	cgoCflags += "-I" + tmpdir
+
+	cgoLdflags := os.Getenv("CGO_LDFLAGS")
+	if cgoLdflags != "" {
+		cgoLdflags += " "
+	}
+	cgoLdflags += "-L" + tmpdir + " -ltestgo2c2go"
+
+	goenv := []string{"CGO_CFLAGS=" + cgoCflags, "CGO_LDFLAGS=" + cgoLdflags}
+
+	ldLibPath := os.Getenv("LD_LIBRARY_PATH")
+	if ldLibPath != "" {
+		ldLibPath += ":"
+	}
+	ldLibPath += tmpdir
+
+	runenv := []string{"LD_LIBRARY_PATH=" + ldLibPath}
+
+	bin := filepath.Join(tmpdir, "m1") + exeSuffix
+	run(t, goenv, "go", "build", "-o", bin, "./go2c2go/m1")
+	runExe(t, runenv, bin)
+
+	bin = filepath.Join(tmpdir, "m2") + exeSuffix
+	run(t, goenv, "go", "build", "-o", bin, "./go2c2go/m2")
+	runExe(t, runenv, bin)
+}