libgo: update to Go1.14beta1

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/214297

28 files changed, 755 insertions, 296 deletions

diff --git a/libgo/misc/cgo/fortran/test.bash b/libgo/misc/cgo/fortran/test.bash
index 9498da0..2b61730 100644
--- a/libgo/misc/cgo/fortran/test.bash
+++ b/libgo/misc/cgo/fortran/test.bash
@@ -28,7 +28,7 @@ case "$FC" in
   ;;
 esac
 
-if ! $FC helloworld/helloworld.f90 -o main.exe >& /dev/null; then
+if ! $FC helloworld/helloworld.f90 -o /dev/null >& /dev/null; then
   echo "skipping Fortran test: could not build helloworld.f90 with $FC"
   exit 0
 fi
diff --git a/libgo/misc/cgo/life/overlaydir_test.go b/libgo/misc/cgo/life/overlaydir_test.go
index f381ea6..034c836 100644
--- a/libgo/misc/cgo/life/overlaydir_test.go
+++ b/libgo/misc/cgo/life/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/stdio/overlaydir_test.go b/libgo/misc/cgo/stdio/overlaydir_test.go
index 8a8dcdb..027ebf1 100644
--- a/libgo/misc/cgo/stdio/overlaydir_test.go
+++ b/libgo/misc/cgo/stdio/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/test/cgo_test.go b/libgo/misc/cgo/test/cgo_test.go
index c66df2c..b745a44 100644
--- a/libgo/misc/cgo/test/cgo_test.go
+++ b/libgo/misc/cgo/test/cgo_test.go
@@ -58,6 +58,7 @@ func Test27660(t *testing.T)                 { test27660(t) }
 func Test28896(t *testing.T)                 { test28896(t) }
 func Test30065(t *testing.T)                 { test30065(t) }
 func Test32579(t *testing.T)                 { test32579(t) }
+func Test31891(t *testing.T)                 { test31891(t) }
 func TestAlign(t *testing.T)                 { testAlign(t) }
 func TestAtol(t *testing.T)                  { testAtol(t) }
 func TestBlocking(t *testing.T)              { testBlocking(t) }
@@ -91,5 +92,6 @@ func TestThreadLock(t *testing.T)            { testThreadLockFunc(t) }
 func TestUnsignedInt(t *testing.T)           { testUnsignedInt(t) }
 func TestZeroArgCallback(t *testing.T)       { testZeroArgCallback(t) }
 
-func BenchmarkCgoCall(b *testing.B)  { benchCgoCall(b) }
-func BenchmarkGoString(b *testing.B) { benchGoString(b) }
+func BenchmarkCgoCall(b *testing.B)     { benchCgoCall(b) }
+func BenchmarkGoString(b *testing.B)    { benchGoString(b) }
+func BenchmarkCGoCallback(b *testing.B) { benchCallback(b) }
diff --git a/libgo/misc/cgo/test/issue31891.c b/libgo/misc/cgo/test/issue31891.c
new file mode 100644
index 0000000..67a0dda
--- /dev/null
+++ b/libgo/misc/cgo/test/issue31891.c
@@ -0,0 +1,13 @@
+// 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.
+
+#include "_cgo_export.h"
+
+void callIssue31891() {
+    Issue31891A a;
+    useIssue31891A(&a);
+
+    Issue31891B b;
+    useIssue31891B(&b);
+}
diff --git a/libgo/misc/cgo/test/issue8945.go b/libgo/misc/cgo/test/issue8945.go
deleted file mode 100644
index 57a5b2d..0000000
--- a/libgo/misc/cgo/test/issue8945.go
+++ /dev/null
@@ -1,16 +0,0 @@
-// Copyright 2014 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 gccgo
-
-package cgotest
-
-//typedef void (*PFunc)();
-//PFunc success_cb;
-import "C"
-
-//export Test
-func Test() {
-	_ = C.success_cb
-}
diff --git a/libgo/misc/cgo/test/overlaydir_test.go b/libgo/misc/cgo/test/overlaydir_test.go
index 1b5c67d..f651979 100644
--- a/libgo/misc/cgo/test/overlaydir_test.go
+++ b/libgo/misc/cgo/test/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/test/test.go b/libgo/misc/cgo/test/test.go
index 2d060bf..b014899 100644
--- a/libgo/misc/cgo/test/test.go
+++ b/libgo/misc/cgo/test/test.go
@@ -115,6 +115,44 @@ int add(int x, int y) {
 	return x+y;
 };
 
+// Following mimicks vulkan complex definitions for benchmarking cgocheck overhead.
+
+typedef uint32_t VkFlags;
+typedef VkFlags  VkDeviceQueueCreateFlags;
+typedef uint32_t VkStructureType;
+
+typedef struct VkDeviceQueueCreateInfo {
+    VkStructureType             sType;
+    const void*                 pNext;
+    VkDeviceQueueCreateFlags    flags;
+    uint32_t                    queueFamilyIndex;
+    uint32_t                    queueCount;
+    const float*                pQueuePriorities;
+} VkDeviceQueueCreateInfo;
+
+typedef struct VkPhysicalDeviceFeatures {
+    uint32_t bools[56];
+} VkPhysicalDeviceFeatures;
+
+typedef struct VkDeviceCreateInfo {
+    VkStructureType                    sType;
+    const void*                        pNext;
+    VkFlags                            flags;
+    uint32_t                           queueCreateInfoCount;
+    const VkDeviceQueueCreateInfo*     pQueueCreateInfos;
+    uint32_t                           enabledLayerCount;
+    const char* const*                 ppEnabledLayerNames;
+    uint32_t                           enabledExtensionCount;
+    const char* const*                 ppEnabledExtensionNames;
+    const VkPhysicalDeviceFeatures*    pEnabledFeatures;
+} VkDeviceCreateInfo;
+
+void handleComplexPointer(VkDeviceCreateInfo *a0) {}
+void handleComplexPointer8(
+	VkDeviceCreateInfo *a0, VkDeviceCreateInfo *a1, VkDeviceCreateInfo *a2, VkDeviceCreateInfo *a3,
+	VkDeviceCreateInfo *a4, VkDeviceCreateInfo *a5, VkDeviceCreateInfo *a6, VkDeviceCreateInfo *a7
+) {}
+
 // complex alignment
 
 struct {
@@ -524,6 +562,11 @@ void issue8811Execute() {
 		issue8811Init();
 }
 
+// issue 8945
+
+typedef void (*PFunc8945)();
+PFunc8945 func8945;
+
 // issue 9557
 
 struct issue9557_t {
@@ -993,10 +1036,55 @@ type Context struct {
 }
 
 func benchCgoCall(b *testing.B) {
-	const x = C.int(2)
-	const y = C.int(3)
+	b.Run("add-int", func(b *testing.B) {
+		const x = C.int(2)
+		const y = C.int(3)
+
+		for i := 0; i < b.N; i++ {
+			C.add(x, y)
+		}
+	})
+
+	b.Run("one-pointer", func(b *testing.B) {
+		var a0 C.VkDeviceCreateInfo
+		for i := 0; i < b.N; i++ {
+			C.handleComplexPointer(&a0)
+		}
+	})
+	b.Run("eight-pointers", func(b *testing.B) {
+		var a0, a1, a2, a3, a4, a5, a6, a7 C.VkDeviceCreateInfo
+		for i := 0; i < b.N; i++ {
+			C.handleComplexPointer8(&a0, &a1, &a2, &a3, &a4, &a5, &a6, &a7)
+		}
+	})
+	b.Run("eight-pointers-nil", func(b *testing.B) {
+		var a0, a1, a2, a3, a4, a5, a6, a7 *C.VkDeviceCreateInfo
+		for i := 0; i < b.N; i++ {
+			C.handleComplexPointer8(a0, a1, a2, a3, a4, a5, a6, a7)
+		}
+	})
+	b.Run("eight-pointers-array", func(b *testing.B) {
+		var a [8]C.VkDeviceCreateInfo
+		for i := 0; i < b.N; i++ {
+			C.handleComplexPointer8(&a[0], &a[1], &a[2], &a[3], &a[4], &a[5], &a[6], &a[7])
+		}
+	})
+	b.Run("eight-pointers-slice", func(b *testing.B) {
+		a := make([]C.VkDeviceCreateInfo, 8)
+		for i := 0; i < b.N; i++ {
+			C.handleComplexPointer8(&a[0], &a[1], &a[2], &a[3], &a[4], &a[5], &a[6], &a[7])
+		}
+	})
+}
+
+// Benchmark measuring overhead from Go to C and back to Go (via a callback)
+func benchCallback(b *testing.B) {
+	var x = false
 	for i := 0; i < b.N; i++ {
-		C.add(x, y)
+		nestedCall(func() { x = true })
+	}
+	if !x {
+		b.Fatal("nestedCall was not invoked")
 	}
 }
 
@@ -1956,12 +2044,14 @@ func test27660(t *testing.T) {
 				locks[j].Lock()
 				ints[j]++
 				locks[j].Unlock()
-				// Avoid making the loop unpreemptible
-				// for gccgo.
-				if i%0x1000000 == 0 {
+				// needed for gccgo, to avoid creation of an
+				// unpreemptible "fast path" in this loop. Choice
+				// of (1<<24) is somewhat arbitrary.
+				if i%(1<<24) == 0 {
 					runtime.Gosched()
 				}
 				i++
+
 			}
 		}()
 		time.Sleep(time.Millisecond)
diff --git a/libgo/misc/cgo/test/testdata/issue9026/issue9026.go b/libgo/misc/cgo/test/testdata/issue9026/issue9026.go
index 149c265..ff269ca 100644
--- a/libgo/misc/cgo/test/testdata/issue9026/issue9026.go
+++ b/libgo/misc/cgo/test/testdata/issue9026/issue9026.go
@@ -4,9 +4,9 @@ package issue9026
 // per-package counter used to create fresh identifiers.
 
 /*
-typedef struct {} git_merge_file_input;
+typedef struct { int i; } git_merge_file_input;
 
-typedef struct {} git_merge_file_options;
+typedef struct { int j; } git_merge_file_options;
 
 void git_merge_file(
         git_merge_file_input *in,
@@ -29,7 +29,7 @@ func Test(t *testing.T) {
 	// Brittle: the assertion may fail spuriously when the algorithm
 	// changes, but should remain stable otherwise.
 	got := fmt.Sprintf("%T %T", in, opts)
-	want := "issue9026._Ctype_struct___0 *issue9026._Ctype_struct___0"
+	want := "issue9026._Ctype_struct___0 *issue9026._Ctype_struct___1"
 	if got != want {
 		t.Errorf("Non-deterministic type names: got %s, want %s", got, want)
 	}
diff --git a/libgo/misc/cgo/test/testx.go b/libgo/misc/cgo/test/testx.go
index 67def90..42979b5 100644
--- a/libgo/misc/cgo/test/testx.go
+++ b/libgo/misc/cgo/test/testx.go
@@ -102,12 +102,28 @@ static void issue7978c(uint32_t *sync) {
 // #include'd twice.  No runtime test; just make sure it compiles.
 #include "issue8331.h"
 
+// issue 8945
+
+typedef void (*PFunc8945)();
+extern PFunc8945 func8945; // definition is in test.go
+
 // issue 20910
 void callMulti(void);
 
 // issue 28772 part 2 - part 1 in issuex.go
 #define issue28772Constant2 2
 
+
+// issue 31891
+typedef struct {
+	long obj;
+} Issue31891A;
+
+typedef struct {
+	long obj;
+} Issue31891B;
+
+void callIssue31891(void);
 */
 import "C"
 
@@ -503,6 +519,13 @@ func test7978(t *testing.T) {
 
 var issue8331Var C.issue8331
 
+// issue 8945
+
+//export Test8945
+func Test8945() {
+	_ = C.func8945
+}
+
 // issue 20910
 
 //export multi
@@ -517,3 +540,15 @@ func test20910(t *testing.T) {
 // issue 28772 part 2
 
 const issue28772Constant2 = C.issue28772Constant2
+
+// issue 31891
+
+//export useIssue31891A
+func useIssue31891A(c *C.Issue31891A) {}
+
+//export useIssue31891B
+func useIssue31891B(c *C.Issue31891B) {}
+
+func test31891(t *testing.T) {
+	C.callIssue31891()
+}
diff --git a/libgo/misc/cgo/testasan/main.go b/libgo/misc/cgo/testasan/main.go
index 1837c6c..bc77678 100644
--- a/libgo/misc/cgo/testasan/main.go
+++ b/libgo/misc/cgo/testasan/main.go
@@ -36,14 +36,21 @@ thread(void *p)
 import "C"
 
 import (
+	"fmt"
+	"os"
+	"path/filepath"
 	"time"
 )
 
 func main() {
+	start := time.Now()
+
 	// ensure that we can function normally
 	var v [][]byte
 	for i := 0; i < 1000; i++ {
 		time.Sleep(10 * time.Microsecond)
 		v = append(v, make([]byte, 64<<10))
 	}
+
+	fmt.Printf("ok\t%s\t%s\n", filepath.Base(os.Args[0]), time.Since(start).Round(time.Millisecond))
 }
diff --git a/libgo/misc/cgo/testcarchive/carchive_test.go b/libgo/misc/cgo/testcarchive/carchive_test.go
index 7051670..98cd41a 100644
--- a/libgo/misc/cgo/testcarchive/carchive_test.go
+++ b/libgo/misc/cgo/testcarchive/carchive_test.go
@@ -36,7 +36,10 @@ var exeSuffix string
 var GOOS, GOARCH, GOPATH string
 var libgodir string
 
+var testWork bool // If true, preserve temporary directories.
+
 func TestMain(m *testing.M) {
+	flag.BoolVar(&testWork, "testwork", false, "if true, log and preserve the test's temporary working directory")
 	flag.Parse()
 	if testing.Short() && os.Getenv("GO_BUILDER_NAME") == "" {
 		fmt.Printf("SKIP - short mode and $GO_BUILDER_NAME not set\n")
@@ -54,7 +57,11 @@ func testMain(m *testing.M) int {
 	if err != nil {
 		log.Panic(err)
 	}
-	defer os.RemoveAll(GOPATH)
+	if testWork {
+		log.Println(GOPATH)
+	} else {
+		defer os.RemoveAll(GOPATH)
+	}
 	os.Setenv("GOPATH", GOPATH)
 
 	// Copy testdata into GOPATH/src/testarchive, along with a go.mod file
@@ -164,6 +171,38 @@ func cmdToRun(name string) []string {
 	return []string{executor, name}
 }
 
+// genHeader writes a C header file for the C-exported declarations found in .go
+// source files in dir.
+//
+// TODO(golang.org/issue/35715): This should be simpler.
+func genHeader(t *testing.T, header, dir string) {
+	t.Helper()
+
+	// 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 := ioutil.TempDir(GOPATH, "_obj")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(objDir)
+
+	files, err := filepath.Glob(filepath.Join(dir, "*.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cmd := exec.Command("go", "tool", "cgo",
+		"-objdir", objDir,
+		"-exportheader", header)
+	cmd.Args = append(cmd.Args, files...)
+	t.Log(cmd.Args)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Logf("%s", out)
+		t.Fatal(err)
+	}
+}
+
 func testInstall(t *testing.T, exe, libgoa, libgoh string, buildcmd ...string) {
 	t.Helper()
 	cmd := exec.Command(buildcmd[0], buildcmd[1:]...)
@@ -172,10 +211,12 @@ func testInstall(t *testing.T, exe, libgoa, libgoh string, buildcmd ...string) {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}
-	defer func() {
-		os.Remove(libgoa)
-		os.Remove(libgoh)
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove(libgoa)
+			os.Remove(libgoh)
+		}()
+	}
 
 	ccArgs := append(cc, "-o", exe, "main.c")
 	if GOOS == "windows" {
@@ -191,7 +232,9 @@ func testInstall(t *testing.T, exe, libgoa, libgoh string, buildcmd ...string) {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}
-	defer os.Remove(exe)
+	if !testWork {
+		defer os.Remove(exe)
+	}
 
 	binArgs := append(cmdToRun(exe), "arg1", "arg2")
 	cmd = exec.Command(binArgs[0], binArgs[1:]...)
@@ -227,17 +270,27 @@ func checkLineComments(t *testing.T, hdrname string) {
 }
 
 func TestInstall(t *testing.T) {
-	defer os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+	if !testWork {
+		defer os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+	}
 
 	libgoa := "libgo.a"
 	if runtime.Compiler == "gccgo" {
 		libgoa = "liblibgo.a"
 	}
 
+	// Generate the p.h header file.
+	//
+	// 'go install -i -buildmode=c-archive ./libgo' would do that too, but that
+	// would also attempt to install transitive standard-library dependencies to
+	// GOROOT, and we cannot assume that GOROOT is writable. (A non-root user may
+	// be running this test in a GOROOT owned by root.)
+	genHeader(t, "p.h", "./p")
+
 	testInstall(t, "./testp1"+exeSuffix,
 		filepath.Join(libgodir, libgoa),
 		filepath.Join(libgodir, "libgo.h"),
-		"go", "install", "-i", "-buildmode=c-archive", "./libgo")
+		"go", "install", "-buildmode=c-archive", "./libgo")
 
 	// Test building libgo other than installing it.
 	// Header files are now present.
@@ -259,12 +312,14 @@ func TestEarlySignalHandler(t *testing.T) {
 		t.Skip("skipping signal test on Windows")
 	}
 
-	defer func() {
-		os.Remove("libgo2.a")
-		os.Remove("libgo2.h")
-		os.Remove("testp")
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo2.a")
+			os.Remove("libgo2.h")
+			os.Remove("testp")
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo2.a", "./libgo2")
 	if out, err := cmd.CombinedOutput(); err != nil {
@@ -282,7 +337,13 @@ func TestEarlySignalHandler(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if out, err := exec.Command(bin[0], bin[1:]...).CombinedOutput(); err != nil {
+	darwin := "0"
+	if runtime.GOOS == "darwin" {
+		darwin = "1"
+	}
+	cmd = exec.Command(bin[0], append(bin[1:], darwin)...)
+
+	if out, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}
@@ -291,12 +352,14 @@ func TestEarlySignalHandler(t *testing.T) {
 func TestSignalForwarding(t *testing.T) {
 	checkSignalForwardingTest(t)
 
-	defer func() {
-		os.Remove("libgo2.a")
-		os.Remove("libgo2.h")
-		os.Remove("testp")
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo2.a")
+			os.Remove("libgo2.h")
+			os.Remove("testp")
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo2.a", "./libgo2")
 	if out, err := cmd.CombinedOutput(); err != nil {
@@ -320,12 +383,15 @@ func TestSignalForwarding(t *testing.T) {
 	t.Logf("%s", out)
 	expectSignal(t, err, syscall.SIGSEGV)
 
-	// Test SIGPIPE forwarding
-	cmd = exec.Command(bin[0], append(bin[1:], "3")...)
+	// SIGPIPE is never forwarded on darwin. See golang.org/issue/33384.
+	if runtime.GOOS != "darwin" {
+		// Test SIGPIPE forwarding
+		cmd = exec.Command(bin[0], append(bin[1:], "3")...)
 
-	out, err = cmd.CombinedOutput()
-	t.Logf("%s", out)
-	expectSignal(t, err, syscall.SIGPIPE)
+		out, err = cmd.CombinedOutput()
+		t.Logf("%s", out)
+		expectSignal(t, err, syscall.SIGPIPE)
+	}
 }
 
 func TestSignalForwardingExternal(t *testing.T) {
@@ -336,12 +402,14 @@ func TestSignalForwardingExternal(t *testing.T) {
 	}
 	checkSignalForwardingTest(t)
 
-	defer func() {
-		os.Remove("libgo2.a")
-		os.Remove("libgo2.h")
-		os.Remove("testp")
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo2.a")
+			os.Remove("libgo2.h")
+			os.Remove("testp")
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo2.a", "./libgo2")
 	if out, err := cmd.CombinedOutput(); err != nil {
@@ -451,12 +519,14 @@ func TestOsSignal(t *testing.T) {
 		t.Skip("skipping signal test on Windows")
 	}
 
-	defer func() {
-		os.Remove("libgo3.a")
-		os.Remove("libgo3.h")
-		os.Remove("testp")
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo3.a")
+			os.Remove("libgo3.h")
+			os.Remove("testp")
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo3.a", "./libgo3")
 	if out, err := cmd.CombinedOutput(); err != nil {
@@ -486,12 +556,14 @@ func TestSigaltstack(t *testing.T) {
 		t.Skip("skipping signal test on Windows")
 	}
 
-	defer func() {
-		os.Remove("libgo4.a")
-		os.Remove("libgo4.h")
-		os.Remove("testp")
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo4.a")
+			os.Remove("libgo4.h")
+			os.Remove("testp")
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo4.a", "./libgo4")
 	if out, err := cmd.CombinedOutput(); err != nil {
@@ -535,13 +607,15 @@ func TestExtar(t *testing.T) {
 		t.Skip("shell scripts are not executable on iOS hosts")
 	}
 
-	defer func() {
-		os.Remove("libgo4.a")
-		os.Remove("libgo4.h")
-		os.Remove("testar")
-		os.Remove("testar.ran")
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo4.a")
+			os.Remove("libgo4.h")
+			os.Remove("testar")
+			os.Remove("testar.ran")
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
 
 	os.Remove("testar")
 	dir, err := os.Getwd()
@@ -575,12 +649,22 @@ func TestPIE(t *testing.T) {
 		t.Skipf("skipping PIE test on %s", GOOS)
 	}
 
-	defer func() {
-		os.Remove("testp" + exeSuffix)
-		os.RemoveAll(filepath.Join(GOPATH, "pkg"))
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("testp" + exeSuffix)
+			os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+		}()
+	}
+
+	// Generate the p.h header file.
+	//
+	// 'go install -i -buildmode=c-archive ./libgo' would do that too, but that
+	// would also attempt to install transitive standard-library dependencies to
+	// GOROOT, and we cannot assume that GOROOT is writable. (A non-root user may
+	// be running this test in a GOROOT owned by root.)
+	genHeader(t, "p.h", "./p")
 
-	cmd := exec.Command("go", "install", "-i", "-buildmode=c-archive", "./libgo")
+	cmd := exec.Command("go", "install", "-buildmode=c-archive", "./libgo")
 	if out, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
@@ -660,11 +744,13 @@ func TestSIGPROF(t *testing.T) {
 
 	t.Parallel()
 
-	defer func() {
-		os.Remove("testp6" + exeSuffix)
-		os.Remove("libgo6.a")
-		os.Remove("libgo6.h")
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("testp6" + exeSuffix)
+			os.Remove("libgo6.a")
+			os.Remove("libgo6.h")
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo6.a", "./libgo6")
 	if out, err := cmd.CombinedOutput(); err != nil {
@@ -700,10 +786,12 @@ func TestCompileWithoutShared(t *testing.T) {
 	// For simplicity, reuse the signal forwarding test.
 	checkSignalForwardingTest(t)
 
-	defer func() {
-		os.Remove("libgo2.a")
-		os.Remove("libgo2.h")
-	}()
+	if !testWork {
+		defer func() {
+			os.Remove("libgo2.a")
+			os.Remove("libgo2.h")
+		}()
+	}
 
 	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-gcflags=-shared=false", "-o", "libgo2.a", "./libgo2")
 	t.Log(cmd.Args)
@@ -742,23 +830,35 @@ func TestCompileWithoutShared(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	defer os.Remove(exe)
+	if !testWork {
+		defer os.Remove(exe)
+	}
 
-	binArgs := append(cmdToRun(exe), "3")
+	binArgs := append(cmdToRun(exe), "1")
 	t.Log(binArgs)
 	out, err = exec.Command(binArgs[0], binArgs[1:]...).CombinedOutput()
 	t.Logf("%s", out)
-	expectSignal(t, err, syscall.SIGPIPE)
+	expectSignal(t, err, syscall.SIGSEGV)
+
+	// SIGPIPE is never forwarded on darwin. See golang.org/issue/33384.
+	if runtime.GOOS != "darwin" {
+		binArgs := append(cmdToRun(exe), "3")
+		t.Log(binArgs)
+		out, err = exec.Command(binArgs[0], binArgs[1:]...).CombinedOutput()
+		t.Logf("%s", out)
+		expectSignal(t, err, syscall.SIGPIPE)
+	}
 }
 
-// Test that installing a second time recreates the header files.
+// Test that installing a second time recreates the header file.
 func TestCachedInstall(t *testing.T) {
-	defer os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+	if !testWork {
+		defer os.RemoveAll(filepath.Join(GOPATH, "pkg"))
+	}
 
-	h1 := filepath.Join(libgodir, "libgo.h")
-	h2 := filepath.Join(libgodir, "p.h")
+	h := filepath.Join(libgodir, "libgo.h")
 
-	buildcmd := []string{"go", "install", "-i", "-buildmode=c-archive", "./libgo"}
+	buildcmd := []string{"go", "install", "-buildmode=c-archive", "./libgo"}
 
 	cmd := exec.Command(buildcmd[0], buildcmd[1:]...)
 	t.Log(buildcmd)
@@ -767,17 +867,11 @@ func TestCachedInstall(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if _, err := os.Stat(h1); err != nil {
+	if _, err := os.Stat(h); err != nil {
 		t.Errorf("libgo.h not installed: %v", err)
 	}
-	if _, err := os.Stat(h2); err != nil {
-		t.Errorf("p.h not installed: %v", err)
-	}
 
-	if err := os.Remove(h1); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.Remove(h2); err != nil {
+	if err := os.Remove(h); err != nil {
 		t.Fatal(err)
 	}
 
@@ -788,10 +882,58 @@ func TestCachedInstall(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if _, err := os.Stat(h1); err != nil {
+	if _, err := os.Stat(h); err != nil {
 		t.Errorf("libgo.h not installed in second run: %v", err)
 	}
-	if _, err := os.Stat(h2); err != nil {
-		t.Errorf("p.h not installed in second run: %v", err)
+}
+
+// Issue 35294.
+func TestManyCalls(t *testing.T) {
+	t.Parallel()
+
+	if !testWork {
+		defer func() {
+			os.Remove("testp7" + exeSuffix)
+			os.Remove("libgo7.a")
+			os.Remove("libgo7.h")
+		}()
+	}
+
+	cmd := exec.Command("go", "build", "-buildmode=c-archive", "-o", "libgo7.a", "./libgo7")
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Logf("%s", out)
+		t.Fatal(err)
+	}
+	checkLineComments(t, "libgo7.h")
+
+	ccArgs := append(cc, "-o", "testp7"+exeSuffix, "main7.c", "libgo7.a")
+	if runtime.Compiler == "gccgo" {
+		ccArgs = append(ccArgs, "-lgo")
+	}
+	if out, err := exec.Command(ccArgs[0], ccArgs[1:]...).CombinedOutput(); err != nil {
+		t.Logf("%s", out)
+		t.Fatal(err)
+	}
+
+	argv := cmdToRun("./testp7")
+	cmd = exec.Command(argv[0], argv[1:]...)
+	var sb strings.Builder
+	cmd.Stdout = &sb
+	cmd.Stderr = &sb
+	if err := cmd.Start(); err != nil {
+		t.Fatal(err)
+	}
+
+	timer := time.AfterFunc(time.Minute,
+		func() {
+			t.Error("test program timed out")
+			cmd.Process.Kill()
+		},
+	)
+	defer timer.Stop()
+
+	if err := cmd.Wait(); err != nil {
+		t.Log(sb.String())
+		t.Error(err)
 	}
 }
diff --git a/libgo/misc/cgo/testcarchive/overlaydir_test.go b/libgo/misc/cgo/testcarchive/overlaydir_test.go
index 68878e4..67974c5 100644
--- a/libgo/misc/cgo/testcarchive/overlaydir_test.go
+++ b/libgo/misc/cgo/testcarchive/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/testcarchive/testdata/libgo7/sink.go b/libgo/misc/cgo/testcarchive/testdata/libgo7/sink.go
new file mode 100644
index 0000000..d61638b
--- /dev/null
+++ b/libgo/misc/cgo/testcarchive/testdata/libgo7/sink.go
@@ -0,0 +1,17 @@
+// 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 main
+
+import "C"
+
+var sink []byte
+
+//export GoFunction7
+func GoFunction7() {
+	sink = make([]byte, 4096)
+}
+
+func main() {
+}
diff --git a/libgo/misc/cgo/testcarchive/testdata/main2.c b/libgo/misc/cgo/testcarchive/testdata/main2.c
index 769cd49..da35673 100644
--- a/libgo/misc/cgo/testcarchive/testdata/main2.c
+++ b/libgo/misc/cgo/testcarchive/testdata/main2.c
@@ -123,8 +123,12 @@ int main(int argc, char** argv) {
 	sigset_t mask;
 	int i;
 	struct timespec ts;
+	int darwin;
+
+	darwin = atoi(argv[1]);
+
+	verbose = argc > 2;
 
-	verbose = argc > 1;
 	setvbuf(stdout, NULL, _IONBF, 0);
 
 	// Call setsid so that we can use kill(0, SIGIO) below.
@@ -186,22 +190,25 @@ int main(int argc, char** argv) {
 		printf("provoking SIGPIPE\n");
 	}
 
-	GoRaiseSIGPIPE();
+	// SIGPIPE is never forwarded on Darwin, see golang.org/issue/33384.
+	if (!darwin) {
+		GoRaiseSIGPIPE();
 
-	if (verbose) {
-		printf("waiting for sigpipeSeen\n");
-	}
+		if (verbose) {
+			printf("waiting for sigpipeSeen\n");
+		}
 
-	// Wait until the signal has been delivered.
-	i = 0;
-	while (!sigpipeSeen) {
-		ts.tv_sec = 0;
-		ts.tv_nsec = 1000000;
-		nanosleep(&ts, NULL);
-		i++;
-		if (i > 5000) {
-			fprintf(stderr, "looping too long waiting for SIGPIPE\n");
-			exit(EXIT_FAILURE);
+		// Wait until the signal has been delivered.
+		i = 0;
+		while (!sigpipeSeen) {
+			ts.tv_sec = 0;
+			ts.tv_nsec = 1000000;
+			nanosleep(&ts, NULL);
+			i++;
+			if (i > 5000) {
+				fprintf(stderr, "looping too long waiting for SIGPIPE\n");
+				exit(EXIT_FAILURE);
+			}
 		}
 	}
 
diff --git a/libgo/misc/cgo/testcarchive/testdata/main3.c b/libgo/misc/cgo/testcarchive/testdata/main3.c
index 60a16cf..4d11d9c 100644
--- a/libgo/misc/cgo/testcarchive/testdata/main3.c
+++ b/libgo/misc/cgo/testcarchive/testdata/main3.c
@@ -12,6 +12,7 @@
 #include <time.h>
 #include <sched.h>
 #include <unistd.h>
+#include <pthread.h>
 
 #include "libgo3.h"
 
@@ -51,11 +52,18 @@ static void init() {
 	}
 }
 
+static void *provokeSIGPIPE(void *arg) {
+	ProvokeSIGPIPE();
+	return NULL;
+}
+
 int main(int argc, char** argv) {
 	int verbose;
 	struct sigaction sa;
 	int i;
 	struct timespec ts;
+	int res;
+	pthread_t tid;
 
 	verbose = argc > 2;
 	setvbuf(stdout, NULL, _IONBF, 0);
@@ -68,6 +76,19 @@ int main(int argc, char** argv) {
 	// a non-default SIGPIPE handler before the runtime initializes.
 	ProvokeSIGPIPE();
 
+	// Test that SIGPIPE on a non-main thread is also handled by Go.
+	res = pthread_create(&tid, NULL, provokeSIGPIPE, NULL);
+	if (res != 0) {
+		fprintf(stderr, "pthread_create: %s\n", strerror(res));
+		exit(EXIT_FAILURE);
+	}
+
+	res = pthread_join(tid, NULL);
+	if (res != 0) {
+		fprintf(stderr, "pthread_join: %s\n", strerror(res));
+		exit(EXIT_FAILURE);
+	}
+
 	if (verbose) {
 		printf("calling sigaction\n");
 	}
diff --git a/libgo/misc/cgo/testcarchive/testdata/main7.c b/libgo/misc/cgo/testcarchive/testdata/main7.c
new file mode 100644
index 0000000..2c6d98d
--- /dev/null
+++ b/libgo/misc/cgo/testcarchive/testdata/main7.c
@@ -0,0 +1,18 @@
+// 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.
+
+// Test that lots of calls don't deadlock.
+
+#include <stdio.h>
+
+#include "libgo7.h"
+
+int main() {
+	int i;
+
+	for (i = 0; i < 100000; i++) {
+		GoFunction7();
+	}
+	return 0;
+}
diff --git a/libgo/misc/cgo/testcshared/cshared_test.go b/libgo/misc/cgo/testcshared/cshared_test.go
index daef3a9..cb95153 100644
--- a/libgo/misc/cgo/testcshared/cshared_test.go
+++ b/libgo/misc/cgo/testcshared/cshared_test.go
@@ -103,7 +103,7 @@ func testMain(m *testing.M) int {
 		// TODO(crawshaw): can we do better?
 		cc = append(cc, []string{"-framework", "CoreFoundation", "-framework", "Foundation"}...)
 	case "android":
-		cc = append(cc, "-pie", "-fuse-ld=gold")
+		cc = append(cc, "-pie")
 	}
 	libgodir := GOOS + "_" + GOARCH
 	switch GOOS {
@@ -130,8 +130,6 @@ func testMain(m *testing.M) int {
 	defer os.RemoveAll(GOPATH)
 	os.Setenv("GOPATH", GOPATH)
 
-	// Copy testdata into GOPATH/src/testarchive, along with a go.mod file
-	// declaring the same path.
 	modRoot := filepath.Join(GOPATH, "src", "testcshared")
 	if err := overlayDir(modRoot, "testdata"); err != nil {
 		log.Panic(err)
@@ -257,14 +255,38 @@ func runCC(t *testing.T, args ...string) string {
 }
 
 func createHeaders() error {
-	args := []string{"go", "install", "-i", "-buildmode=c-shared",
-		"-installsuffix", "testcshared", "./libgo"}
+	// 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 := ioutil.TempDir("", "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,
@@ -522,7 +544,7 @@ func TestPIE(t *testing.T) {
 	}
 }
 
-// Test that installing a second time recreates the header files.
+// Test that installing a second time recreates the header file.
 func TestCachedInstall(t *testing.T) {
 	tmpdir, err := ioutil.TempDir("", "cshared")
 	if err != nil {
@@ -536,7 +558,7 @@ func TestCachedInstall(t *testing.T) {
 
 	env := append(os.Environ(), "GOPATH="+tmpdir, "GOBIN="+filepath.Join(tmpdir, "bin"))
 
-	buildcmd := []string{"go", "install", "-x", "-i", "-buildmode=c-shared", "-installsuffix", "testcshared", "./libgo"}
+	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")
@@ -577,16 +599,10 @@ func TestCachedInstall(t *testing.T) {
 	if libgoh == "" {
 		t.Fatal("libgo.h not installed")
 	}
-	if ph == "" {
-		t.Fatal("p.h not installed")
-	}
 
 	if err := os.Remove(libgoh); err != nil {
 		t.Fatal(err)
 	}
-	if err := os.Remove(ph); err != nil {
-		t.Fatal(err)
-	}
 
 	cmd = exec.Command(buildcmd[0], buildcmd[1:]...)
 	cmd.Dir = filepath.Join(tmpdir, "src", "testcshared")
@@ -601,9 +617,6 @@ func TestCachedInstall(t *testing.T) {
 	if _, err := os.Stat(libgoh); err != nil {
 		t.Errorf("libgo.h not installed in second run: %v", err)
 	}
-	if _, err := os.Stat(ph); err != nil {
-		t.Errorf("p.h not installed in second run: %v", err)
-	}
 }
 
 // copyFile copies src to dst.
diff --git a/libgo/misc/cgo/testcshared/overlaydir_test.go b/libgo/misc/cgo/testcshared/overlaydir_test.go
index 1eaabf6..85d6b44 100644
--- a/libgo/misc/cgo/testcshared/overlaydir_test.go
+++ b/libgo/misc/cgo/testcshared/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/testgodefs/test.bash b/libgo/misc/cgo/testgodefs/test.bash
deleted file mode 100644
index e4ce2ee..0000000
--- a/libgo/misc/cgo/testgodefs/test.bash
+++ /dev/null
@@ -1,24 +0,0 @@
-#!/usr/bin/env bash
-
-# Copyright 2014 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.
-
-# We are testing cgo -godefs, which translates Go files that use
-# import "C" into Go files with Go definitions of types defined in the
-# import "C" block.  Add more tests here.
-FILE_PREFIXES="anonunion issue8478 fieldtypedef"
-
-cd testdata
-
-RM=
-for FP in $FILE_PREFIXES
-do
-  go tool cgo -godefs -srcdir . ${FP}.go > ${FP}_defs.go
-  RM="${RM} ${FP}_defs.go"
-done
-
-go build -o testgodefs . && ./testgodefs
-EXIT=$?
-rm -rf _obj testgodefs ${RM}
-exit $EXIT
diff --git a/libgo/misc/cgo/testgodefs/testgodefs_test.go b/libgo/misc/cgo/testgodefs/testgodefs_test.go
new file mode 100644
index 0000000..c02c3ff
--- /dev/null
+++ b/libgo/misc/cgo/testgodefs/testgodefs_test.go
@@ -0,0 +1,83 @@
+// 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 testgodefs
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// We are testing cgo -godefs, which translates Go files that use
+// import "C" into Go files with Go definitions of types defined in the
+// import "C" block.  Add more tests here.
+var filePrefixes = []string{
+	"anonunion",
+	"issue8478",
+	"fieldtypedef",
+}
+
+func TestGoDefs(t *testing.T) {
+	testdata, err := filepath.Abs("testdata")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	gopath, err := ioutil.TempDir("", "testgodefs-gopath")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(gopath)
+
+	dir := filepath.Join(gopath, "src", "testgodefs")
+	if err := os.MkdirAll(dir, 0755); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, fp := range filePrefixes {
+		cmd := exec.Command("go", "tool", "cgo",
+			"-godefs",
+			"-srcdir", testdata,
+			"-objdir", dir,
+			fp+".go")
+		cmd.Stderr = new(bytes.Buffer)
+
+		out, err := cmd.Output()
+		if err != nil {
+			t.Fatalf("%s: %v\n%s", strings.Join(cmd.Args, " "), err, cmd.Stderr)
+		}
+
+		if err := ioutil.WriteFile(filepath.Join(dir, fp+"_defs.go"), out, 0644); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	main, err := ioutil.ReadFile(filepath.Join("testdata", "main.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := ioutil.WriteFile(filepath.Join(dir, "main.go"), main, 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := ioutil.WriteFile(filepath.Join(dir, "go.mod"), []byte("module testgodefs\ngo 1.14\n"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	// Use 'go run' to build and run the resulting binary in a single step,
+	// instead of invoking 'go build' and the resulting binary separately, so that
+	// this test can pass on mobile builders, which do not copy artifacts back
+	// from remote invocations.
+	cmd := exec.Command("go", "run", ".")
+	cmd.Env = append(os.Environ(), "GOPATH="+gopath)
+	cmd.Dir = dir
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("%s [%s]: %v\n%s", strings.Join(cmd.Args, " "), dir, err, out)
+	}
+}
diff --git a/libgo/misc/cgo/testplugin/overlaydir_test.go b/libgo/misc/cgo/testplugin/overlaydir_test.go
index b68436a..e2c32d8 100644
--- a/libgo/misc/cgo/testplugin/overlaydir_test.go
+++ b/libgo/misc/cgo/testplugin/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/testplugin/plugin_test.go b/libgo/misc/cgo/testplugin/plugin_test.go
index 7e2b6eb..ab98f61 100644
--- a/libgo/misc/cgo/testplugin/plugin_test.go
+++ b/libgo/misc/cgo/testplugin/plugin_test.go
@@ -14,7 +14,6 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"runtime"
 	"strings"
 	"testing"
 	"time"
@@ -71,7 +70,7 @@ func testMain(m *testing.M) int {
 
 	os.Setenv("LD_LIBRARY_PATH", modRoot)
 
-	goCmd(nil, "build", "-i", "-buildmode=plugin", "./plugin1")
+	goCmd(nil, "build", "-buildmode=plugin", "./plugin1")
 	goCmd(nil, "build", "-buildmode=plugin", "./plugin2")
 	so, err := ioutil.ReadFile("plugin2.so")
 	if err != nil {
@@ -114,11 +113,7 @@ func run(t *testing.T, bin string, args ...string) string {
 
 func TestDWARFSections(t *testing.T) {
 	// test that DWARF sections are emitted for plugins and programs importing "plugin"
-	if runtime.GOOS != "darwin" {
-		// On macOS, for some reason, the linker doesn't add debug sections to .so,
-		// see issue #27502.
-		goCmd(t, "run", "./checkdwarf/main.go", "plugin2.so", "plugin2.UnexportedNameReuse")
-	}
+	goCmd(t, "run", "./checkdwarf/main.go", "plugin2.so", "plugin2.UnexportedNameReuse")
 	goCmd(t, "run", "./checkdwarf/main.go", "./host.exe", "main.main")
 }
 
diff --git a/libgo/misc/cgo/testshared/overlaydir_test.go b/libgo/misc/cgo/testshared/overlaydir_test.go
index 68be056..eb587a2 100644
--- a/libgo/misc/cgo/testshared/overlaydir_test.go
+++ b/libgo/misc/cgo/testshared/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/testshared/shared_test.go b/libgo/misc/cgo/testshared/shared_test.go
index 9d16338..b9ef6da 100644
--- a/libgo/misc/cgo/testshared/shared_test.go
+++ b/libgo/misc/cgo/testshared/shared_test.go
@@ -9,31 +9,33 @@ import (
 	"bytes"
 	"debug/elf"
 	"encoding/binary"
-	"errors"
 	"flag"
 	"fmt"
 	"go/build"
 	"io"
 	"io/ioutil"
 	"log"
-	"math/rand"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"regexp"
 	"runtime"
+	"sort"
 	"strings"
 	"testing"
 	"time"
 )
 
-var gopathInstallDir, gorootInstallDir, suffix string
+var gopathInstallDir, gorootInstallDir string
 
 // This is the smallest set of packages we can link into a shared
 // library (runtime/cgo is built implicitly).
 var minpkgs = []string{"runtime", "sync/atomic"}
 var soname = "libruntime,sync-atomic.so"
 
+var testX = flag.Bool("testx", false, "if true, pass -x to 'go' subcommands invoked by the test")
+var testWork = flag.Bool("testwork", false, "if true, log and do not delete the temporary working directory")
+
 // run runs a command and calls t.Errorf if it fails.
 func run(t *testing.T, msg string, args ...string) {
 	c := exec.Command(args[0], args[1:]...)
@@ -45,31 +47,34 @@ func run(t *testing.T, msg string, args ...string) {
 // goCmd invokes the go tool with the installsuffix set up by TestMain. It calls
 // t.Fatalf if the command fails.
 func goCmd(t *testing.T, args ...string) string {
-	newargs := []string{args[0], "-installsuffix=" + suffix}
-	if testing.Verbose() {
+	newargs := []string{args[0]}
+	if *testX {
 		newargs = append(newargs, "-x")
 	}
 	newargs = append(newargs, args[1:]...)
 	c := exec.Command("go", newargs...)
-
 	stderr := new(strings.Builder)
-	var output []byte
-	var err error
-	if testing.Verbose() {
-		fmt.Printf("+ go %s\n", strings.Join(args, " "))
+	c.Stderr = stderr
+
+	if testing.Verbose() && t == nil {
+		fmt.Fprintf(os.Stderr, "+ go %s\n", strings.Join(args, " "))
 		c.Stderr = os.Stderr
-		stderr.WriteString("(output above)")
-	} else {
-		c.Stderr = stderr
 	}
-	output, err = c.Output()
+	output, err := c.Output()
 
 	if err != nil {
 		if t != nil {
 			t.Helper()
 			t.Fatalf("executing %s failed %v:\n%s", strings.Join(c.Args, " "), err, stderr)
 		} else {
-			log.Fatalf("executing %s failed %v:\n%s", strings.Join(c.Args, " "), err, stderr)
+			// Panic instead of using log.Fatalf so that deferred cleanup may run in testMain.
+			log.Panicf("executing %s failed %v:\n%s", strings.Join(c.Args, " "), err, stderr)
+		}
+	}
+	if testing.Verbose() && t != nil {
+		t.Logf("go %s", strings.Join(args, " "))
+		if stderr.Len() > 0 {
+			t.Logf("%s", stderr)
 		}
 	}
 	return string(bytes.TrimSpace(output))
@@ -77,73 +82,61 @@ func goCmd(t *testing.T, args ...string) string {
 
 // TestMain calls testMain so that the latter can use defer (TestMain exits with os.Exit).
 func testMain(m *testing.M) (int, error) {
-	// Because go install -buildmode=shared $standard_library_package always
-	// installs into $GOROOT, here are some gymnastics to come up with a unique
-	// installsuffix to use in this test that we can clean up afterwards.
-	myContext := build.Default
-	runtimeP, err := myContext.Import("runtime", ".", build.ImportComment)
+	workDir, err := ioutil.TempDir("", "shared_test")
 	if err != nil {
-		return 0, fmt.Errorf("import failed: %v", err)
-	}
-	for i := 0; i < 10000; i++ {
-		try := fmt.Sprintf("%s_%d_dynlink", runtimeP.PkgTargetRoot, rand.Int63())
-		err = os.Mkdir(try, 0700)
-		if os.IsExist(err) {
-			continue
-		}
-		if err == nil {
-			gorootInstallDir = try
-		}
-		break
-	}
-	if err != nil {
-		return 0, fmt.Errorf("can't create temporary directory: %v", err)
+		return 0, err
 	}
-	if gorootInstallDir == "" {
-		return 0, errors.New("could not create temporary directory after 10000 tries")
+	if *testWork || testing.Verbose() {
+		fmt.Printf("+ mkdir -p %s\n", workDir)
 	}
-	if testing.Verbose() {
-		fmt.Printf("+ mkdir -p %s\n", gorootInstallDir)
+	if !*testWork {
+		defer os.RemoveAll(workDir)
 	}
-	defer os.RemoveAll(gorootInstallDir)
 
 	// Some tests need to edit the source in GOPATH, so copy this directory to a
 	// temporary directory and chdir to that.
-	gopath, err := ioutil.TempDir("", "testshared")
+	gopath := filepath.Join(workDir, "gopath")
+	modRoot, err := cloneTestdataModule(gopath)
 	if err != nil {
-		return 0, fmt.Errorf("TempDir failed: %v", err)
-	}
-	if testing.Verbose() {
-		fmt.Printf("+ mkdir -p %s\n", gopath)
-	}
-	defer os.RemoveAll(gopath)
-
-	modRoot := filepath.Join(gopath, "src", "testshared")
-	if err := overlayDir(modRoot, "testdata"); err != nil {
 		return 0, err
 	}
 	if testing.Verbose() {
+		fmt.Printf("+ export GOPATH=%s\n", gopath)
 		fmt.Printf("+ cd %s\n", modRoot)
 	}
+	os.Setenv("GOPATH", gopath)
 	os.Chdir(modRoot)
 	os.Setenv("PWD", modRoot)
-	if err := ioutil.WriteFile("go.mod", []byte("module testshared\n"), 0666); err != nil {
+
+	// The test also needs to install libraries into GOROOT/pkg, so copy the
+	// subset of GOROOT that we need.
+	//
+	// TODO(golang.org/issue/28553): Rework -buildmode=shared so that it does not
+	// need to write to GOROOT.
+	goroot := filepath.Join(workDir, "goroot")
+	if err := cloneGOROOTDeps(goroot); err != nil {
 		return 0, err
 	}
-
-	os.Setenv("GOPATH", gopath)
 	if testing.Verbose() {
-		fmt.Printf("+ export GOPATH=%s\n", gopath)
+		fmt.Fprintf(os.Stderr, "+ export GOROOT=%s\n", goroot)
 	}
+	os.Setenv("GOROOT", goroot)
+
+	myContext := build.Default
+	myContext.GOROOT = goroot
 	myContext.GOPATH = gopath
+	runtimeP, err := myContext.Import("runtime", ".", build.ImportComment)
+	if err != nil {
+		return 0, fmt.Errorf("import failed: %v", err)
+	}
+	gorootInstallDir = runtimeP.PkgTargetRoot + "_dynlink"
 
 	// All tests depend on runtime being built into a shared library. Because
 	// that takes a few seconds, do it here and have all tests use the version
 	// built here.
-	suffix = strings.Split(filepath.Base(gorootInstallDir), "_")[2]
 	goCmd(nil, append([]string{"install", "-buildmode=shared"}, minpkgs...)...)
 
-	myContext.InstallSuffix = suffix + "_dynlink"
+	myContext.InstallSuffix = "_dynlink"
 	depP, err := myContext.Import("./depBase", ".", build.ImportComment)
 	if err != nil {
 		return 0, fmt.Errorf("import failed: %v", err)
@@ -171,6 +164,75 @@ func TestMain(m *testing.M) {
 	os.Exit(exitCode)
 }
 
+// cloneTestdataModule clones the packages from src/testshared into gopath.
+// It returns the directory within gopath at which the module root is located.
+func cloneTestdataModule(gopath string) (string, error) {
+	modRoot := filepath.Join(gopath, "src", "testshared")
+	if err := overlayDir(modRoot, "testdata"); err != nil {
+		return "", err
+	}
+	if err := ioutil.WriteFile(filepath.Join(modRoot, "go.mod"), []byte("module testshared\n"), 0644); err != nil {
+		return "", err
+	}
+	return modRoot, nil
+}
+
+// cloneGOROOTDeps copies (or symlinks) the portions of GOROOT/src and
+// GOROOT/pkg relevant to this test into the given directory.
+// It must be run from within the testdata module.
+func cloneGOROOTDeps(goroot string) error {
+	oldGOROOT := strings.TrimSpace(goCmd(nil, "env", "GOROOT"))
+	if oldGOROOT == "" {
+		return fmt.Errorf("go env GOROOT returned an empty string")
+	}
+
+	// Before we clone GOROOT, figure out which packages we need to copy over.
+	listArgs := []string{
+		"list",
+		"-deps",
+		"-f", "{{if and .Standard (not .ForTest)}}{{.ImportPath}}{{end}}",
+	}
+	stdDeps := goCmd(nil, append(listArgs, minpkgs...)...)
+	testdataDeps := goCmd(nil, append(listArgs, "-test", "./...")...)
+
+	pkgs := append(strings.Split(strings.TrimSpace(stdDeps), "\n"),
+		strings.Split(strings.TrimSpace(testdataDeps), "\n")...)
+	sort.Strings(pkgs)
+	var pkgRoots []string
+	for _, pkg := range pkgs {
+		parentFound := false
+		for _, prev := range pkgRoots {
+			if strings.HasPrefix(pkg, prev) {
+				// We will copy in the source for pkg when we copy in prev.
+				parentFound = true
+				break
+			}
+		}
+		if !parentFound {
+			pkgRoots = append(pkgRoots, pkg)
+		}
+	}
+
+	gorootDirs := []string{
+		"pkg/tool",
+		"pkg/include",
+	}
+	for _, pkg := range pkgRoots {
+		gorootDirs = append(gorootDirs, filepath.Join("src", pkg))
+	}
+
+	for _, dir := range gorootDirs {
+		if testing.Verbose() {
+			fmt.Fprintf(os.Stderr, "+ cp -r %s %s\n", filepath.Join(goroot, dir), filepath.Join(oldGOROOT, dir))
+		}
+		if err := overlayDir(filepath.Join(goroot, dir), filepath.Join(oldGOROOT, dir)); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 // The shared library was built at the expected location.
 func TestSOBuilt(t *testing.T) {
 	_, err := os.Stat(filepath.Join(gorootInstallDir, soname))
@@ -219,6 +281,7 @@ func TestNoTextrel(t *testing.T) {
 }
 
 // The shared library does not contain symbols called ".dup"
+// (See golang.org/issue/14841.)
 func TestNoDupSymbols(t *testing.T) {
 	sopath := filepath.Join(gorootInstallDir, soname)
 	f, err := elf.Open(sopath)
@@ -695,7 +758,7 @@ func resetFileStamps() {
 	}
 	reset := func(path string) {
 		if err := filepath.Walk(path, chtime); err != nil {
-			log.Fatalf("resetFileStamps failed: %v", err)
+			log.Panicf("resetFileStamps failed: %v", err)
 		}
 
 	}
@@ -708,6 +771,7 @@ func resetFileStamps() {
 // touch changes path and returns a function that changes it back.
 // It also sets the time of the file, so that we can see if it is rewritten.
 func touch(t *testing.T, path string) (cleanup func()) {
+	t.Helper()
 	data, err := ioutil.ReadFile(path)
 	if err != nil {
 		t.Fatal(err)
@@ -736,14 +800,32 @@ func touch(t *testing.T, path string) (cleanup func()) {
 		// assume it's a text file
 		data = append(data, '\n')
 	}
-	if err := ioutil.WriteFile(path, data, 0666); err != nil {
+
+	// If the file is still a symlink from an overlay, delete it so that we will
+	// replace it with a regular file instead of overwriting the symlinked one.
+	fi, err := os.Lstat(path)
+	if err == nil && !fi.Mode().IsRegular() {
+		fi, err = os.Stat(path)
+		if err := os.Remove(path); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// If we're replacing a symlink to a read-only file, make the new file
+	// user-writable.
+	perm := fi.Mode().Perm() | 0200
+
+	if err := ioutil.WriteFile(path, data, perm); err != nil {
 		t.Fatal(err)
 	}
 	if err := os.Chtimes(path, nearlyNew, nearlyNew); err != nil {
 		t.Fatal(err)
 	}
 	return func() {
-		if err := ioutil.WriteFile(path, old, 0666); err != nil {
+		if err := ioutil.WriteFile(path, old, perm); err != nil {
 			t.Fatal(err)
 		}
 	}
diff --git a/libgo/misc/cgo/testsigfwd/main.go b/libgo/misc/cgo/testsigfwd/main.go
index 61bd0da..6d97050 100644
--- a/libgo/misc/cgo/testsigfwd/main.go
+++ b/libgo/misc/cgo/testsigfwd/main.go
@@ -25,6 +25,7 @@ static void sigsegv() {
 
 static void segvhandler(int signum) {
 	if (signum == SIGSEGV) {
+		fprintf(stdout, "ok\ttestsigfwd\n");
 		exit(0);  // success
 	}
 }
diff --git a/libgo/misc/cgo/testso/overlaydir_test.go b/libgo/misc/cgo/testso/overlaydir_test.go
index 10c874d..09a1d51 100644
--- a/libgo/misc/cgo/testso/overlaydir_test.go
+++ b/libgo/misc/cgo/testso/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}
 
diff --git a/libgo/misc/cgo/testsovar/overlaydir_test.go b/libgo/misc/cgo/testsovar/overlaydir_test.go
index 10c874d..09a1d51 100644
--- a/libgo/misc/cgo/testsovar/overlaydir_test.go
+++ b/libgo/misc/cgo/testsovar/overlaydir_test.go
@@ -21,12 +21,9 @@ func overlayDir(dstRoot, srcRoot string) error {
 		return err
 	}
 
-	symBase, err := filepath.Rel(srcRoot, dstRoot)
+	srcRoot, err := filepath.Abs(srcRoot)
 	if err != nil {
-		symBase, err = filepath.Abs(srcRoot)
-		if err != nil {
-			return err
-		}
+		return err
 	}
 
 	return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
@@ -52,11 +49,11 @@ func overlayDir(dstRoot, srcRoot string) error {
 		// 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)
+			return os.MkdirAll(dstPath, perm|0200)
 		}
 
 		// If the OS supports symlinks, use them instead of copying bytes.
-		if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
+		if err := os.Symlink(srcPath, dstPath); err == nil {
 			return nil
 		}