libgo: update to Go1.10rc1

    
    Reviewed-on: https://go-review.googlesource.com/90295

From-SVN: r257126

39 files changed, 962 insertions, 514 deletions

diff --git a/libgo/MERGE b/libgo/MERGE
index b42c3a7..4a3c64e 100644
--- a/libgo/MERGE
+++ b/libgo/MERGE
@@ -1,4 +1,4 @@
-594668a5a96267a46282ce3007a584ec07adf705
+5348aed83e39bd1d450d92d7f627e994c2db6ebf
 
 The first line of this file holds the git revision number of the
 last merge done from the master library sources.
diff --git a/libgo/VERSION b/libgo/VERSION
index 9c5f795..5859fbe 100644
--- a/libgo/VERSION
+++ b/libgo/VERSION
@@ -1 +1 @@
-go1.10beta2
+go1.10rc1
diff --git a/libgo/go/cmd/cgo/doc.go b/libgo/go/cmd/cgo/doc.go
index 0b64b31..8e4cd88 100644
--- a/libgo/go/cmd/cgo/doc.go
+++ b/libgo/go/cmd/cgo/doc.go
@@ -341,69 +341,11 @@ in unexpected and unpredictable ways.
 Special cases
 
 A few special C types which would normally be represented by a pointer
-type in Go are instead represented by a uintptr. Those types are
-the CF*Ref types from the CoreFoundation library on Darwin, including:
-
-	CFAllocatorRef
-	CFArrayRef
-	CFAttributedStringRef
-	CFBagRef
-	CFBinaryHeapRef
-	CFBitVectorRef
-	CFBooleanRef
-	CFBundleRef
-	CFCalendarRef
-	CFCharacterSetRef
-	CFDataRef
-	CFDateFormatterRef
-	CFDateRef
-	CFDictionaryRef
-	CFErrorRef
-	CFFileDescriptorRef
-	CFFileSecurityRef
-	CFLocaleRef
-	CFMachPortRef
-	CFMessagePortRef
-	CFMutableArrayRef
-	CFMutableAttributedStringRef
-	CFMutableBagRef
-	CFMutableBitVectorRef
-	CFMutableCharacterSetRef
-	CFMutableDataRef
-	CFMutableDictionaryRef
-	CFMutableSetRef
-	CFMutableStringRef
-	CFNotificationCenterRef
-	CFNullRef
-	CFNumberFormatterRef
-	CFNumberRef
-	CFPlugInInstanceRef
-	CFPlugInRef
-	CFPropertyListRef
-	CFReadStreamRef
-	CFRunLoopObserverRef
-	CFRunLoopRef
-	CFRunLoopSourceRef
-	CFRunLoopTimerRef
-	CFSetRef
-	CFSocketRef
-	CFStringRef
-	CFStringTokenizerRef
-	CFTimeZoneRef
-	CFTreeRef
-	CFTypeRef
-	CFURLCreateFromFSRef
-	CFURLEnumeratorRef
-	CFURLGetFSRef
-	CFURLRef
-	CFUUIDRef
-	CFUserNotificationRef
-	CFWriteStreamRef
-	CFXMLNodeRef
-	CFXMLParserRef
-	CFXMLTreeRef
-
-Also the object types from Java's JNI interface:
+type in Go are instead represented by a uintptr. Those include:
+
+1. The *Ref types on Darwin, rooted at CoreFoundation's CFTypeRef type.
+
+2. The object types from Java's JNI interface:
 
 	jobject
 	jclass
diff --git a/libgo/go/cmd/cgo/gcc.go b/libgo/go/cmd/cgo/gcc.go
index d9db573..fcf334e 100644
--- a/libgo/go/cmd/cgo/gcc.go
+++ b/libgo/go/cmd/cgo/gcc.go
@@ -243,6 +243,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 	// Determine kinds for names we already know about,
 	// like #defines or 'struct foo', before bothering with gcc.
 	var names, needType []*Name
+	optional := map[*Name]bool{}
 	for _, key := range nameKeys(f.Name) {
 		n := f.Name[key]
 		// If we've already found this name as a #define
@@ -279,6 +280,14 @@ func (p *Package) guessKinds(f *File) []*Name {
 			continue
 		}
 
+		if goos == "darwin" && strings.HasSuffix(n.C, "Ref") {
+			// For FooRef, find out if FooGetTypeID exists.
+			s := n.C[:len(n.C)-3] + "GetTypeID"
+			n := &Name{Go: s, C: s}
+			names = append(names, n)
+			optional[n] = true
+		}
+
 		// Otherwise, we'll need to find out from gcc.
 		names = append(names, n)
 	}
@@ -425,6 +434,11 @@ func (p *Package) guessKinds(f *File) []*Name {
 	for i, n := range names {
 		switch sniff[i] {
 		default:
+			if sniff[i]&notDeclared != 0 && optional[n] {
+				// Ignore optional undeclared identifiers.
+				// Don't report an error, and skip adding n to the needType array.
+				continue
+			}
 			error_(f.NamePos[n], "could not determine kind of name for C.%s", fixGo(n.Go))
 		case notStrLiteral | notType:
 			n.Kind = "iconst"
@@ -437,6 +451,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 		case notIntConst | notNumConst | notStrLiteral | notType:
 			n.Kind = "not-type"
 		}
+		needType = append(needType, n)
 	}
 	if nerrors > 0 {
 		// Check if compiling the preamble by itself causes any errors,
@@ -450,7 +465,6 @@ func (p *Package) guessKinds(f *File) []*Name {
 		fatalf("unresolved names")
 	}
 
-	needType = append(needType, names...)
 	return needType
 }
 
@@ -566,6 +580,11 @@ func (p *Package) loadDWARF(f *File, names []*Name) {
 	var conv typeConv
 	conv.Init(p.PtrSize, p.IntSize)
 	for i, n := range names {
+		if strings.HasSuffix(n.Go, "GetTypeID") && types[i].String() == "func() CFTypeID" {
+			conv.getTypeIDs[n.Go[:len(n.Go)-9]] = true
+		}
+	}
+	for i, n := range names {
 		if types[i] == nil {
 			continue
 		}
@@ -1737,6 +1756,9 @@ type typeConv struct {
 	// Keys of ptrs in insertion order (deterministic worklist)
 	ptrKeys []dwarf.Type
 
+	// Type names X for which there exists an XGetTypeID function with type func() CFTypeID.
+	getTypeIDs map[string]bool
+
 	// Predeclared types.
 	bool                                   ast.Expr
 	byte                                   ast.Expr // denotes padding
@@ -1766,6 +1788,7 @@ func (c *typeConv) Init(ptrSize, intSize int64) {
 	c.intSize = intSize
 	c.m = make(map[dwarf.Type]*Type)
 	c.ptrs = make(map[dwarf.Type][]*Type)
+	c.getTypeIDs = make(map[string]bool)
 	c.bool = c.Ident("bool")
 	c.byte = c.Ident("byte")
 	c.int8 = c.Ident("int8")
@@ -2152,7 +2175,7 @@ func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
 		name := c.Ident("_Ctype_" + dt.Name)
 		goIdent[name.Name] = name
 		sub := c.Type(dt.Type, pos)
-		if badPointerTypedef(dt) {
+		if c.badPointerTypedef(dt) {
 			// Treat this typedef as a uintptr.
 			s := *sub
 			s.Go = c.uintptr
@@ -2318,7 +2341,7 @@ func (c *typeConv) FuncArg(dtype dwarf.Type, pos token.Pos) *Type {
 			}
 			// ...or the typedef is one in which we expect bad pointers.
 			// It will be a uintptr instead of *X.
-			if badPointerTypedef(dt) {
+			if c.badPointerTypedef(dt) {
 				break
 			}
 
@@ -2666,23 +2689,43 @@ func fieldPrefix(fld []*ast.Field) string {
 // A typedef is bad if C code sometimes stores non-pointers in this type.
 // TODO: Currently our best solution is to find these manually and list them as
 // they come up. A better solution is desired.
-func badPointerTypedef(dt *dwarf.TypedefType) bool {
-	if badCFType(dt) {
+func (c *typeConv) badPointerTypedef(dt *dwarf.TypedefType) bool {
+	if c.badCFType(dt) {
 		return true
 	}
-	if badJNI(dt) {
+	if c.badJNI(dt) {
 		return true
 	}
 	return false
 }
 
-func badCFType(dt *dwarf.TypedefType) bool {
+func (c *typeConv) badCFType(dt *dwarf.TypedefType) bool {
 	// The real bad types are CFNumberRef and CFDateRef.
 	// Sometimes non-pointers are stored in these types.
 	// CFTypeRef is a supertype of those, so it can have bad pointers in it as well.
-	// We return true for the other CF*Ref types just so casting between them is easier.
+	// We return true for the other *Ref types just so casting between them is easier.
+	// We identify the correct set of types as those ending in Ref and for which
+	// there exists a corresponding GetTypeID function.
 	// See comment below for details about the bad pointers.
-	return goos == "darwin" && strings.HasPrefix(dt.Name, "CF") && strings.HasSuffix(dt.Name, "Ref")
+	if goos != "darwin" {
+		return false
+	}
+	s := dt.Name
+	if !strings.HasSuffix(s, "Ref") {
+		return false
+	}
+	s = s[:len(s)-3]
+	if s == "CFType" {
+		return true
+	}
+	if c.getTypeIDs[s] {
+		return true
+	}
+	if i := strings.Index(s, "Mutable"); i >= 0 && c.getTypeIDs[s[:i]+s[i+7:]] {
+		// Mutable and immutable variants share a type ID.
+		return true
+	}
+	return false
 }
 
 // Comment from Darwin's CFInternal.h
@@ -2720,7 +2763,7 @@ enum {
 };
 */
 
-func badJNI(dt *dwarf.TypedefType) bool {
+func (c *typeConv) badJNI(dt *dwarf.TypedefType) bool {
 	// In Dalvik and ART, the jobject type in the JNI interface of the JVM has the
 	// property that it is sometimes (always?) a small integer instead of a real pointer.
 	// Note: although only the android JVMs are bad in this respect, we declare the JNI types
diff --git a/libgo/go/cmd/go/alldocs.go b/libgo/go/cmd/go/alldocs.go
index c151fa6..85b9d25 100644
--- a/libgo/go/cmd/go/alldocs.go
+++ b/libgo/go/cmd/go/alldocs.go
@@ -35,14 +35,15 @@
 // Additional help topics:
 //
 // 	c           calling between Go and C
-// 	buildmode   description of build modes
+// 	buildmode   build modes
+// 	cache       build and test caching
 // 	filetype    file types
 // 	gopath      GOPATH environment variable
 // 	environment environment variables
 // 	importpath  import path syntax
-// 	packages    description of package lists
-// 	testflag    description of testing flags
-// 	testfunc    description of testing functions
+// 	packages    package lists
+// 	testflag    testing flags
+// 	testfunc    testing functions
 //
 // Use "go help [topic]" for more information about that topic.
 //
@@ -756,39 +757,51 @@
 // Only a high-confidence subset of the default go vet checks are used.
 // To disable the running of go vet, use the -vet=off flag.
 //
-// Go test runs in two different modes: local directory mode when invoked with
-// no package arguments (for example, 'go test'), and package list mode when
-// invoked with package arguments (for example 'go test math', 'go test ./...',
-// and even 'go test .').
-//
-// In local directory mode, go test compiles and tests the package sources
-// found in the current directory and then runs the resulting test binary.
-// In this mode, caching (discussed below) is disabled. After the package test
-// finishes, go test prints a summary line showing the test status ('ok' or 'FAIL'),
-// package name, and elapsed time.
-//
-// In package list mode, go test compiles and tests each of the packages
-// listed on the command line. If a package test passes, go test prints only
-// the final 'ok' summary line. If a package test fails, go test prints the
-// full test output. If invoked with the -bench or -v flag, go test prints
-// the full output even for passing package tests, in order to display the
+// All test output and summary lines are printed to the go command's
+// standard output, even if the test printed them to its own standard
+// error. (The go command's standard error is reserved for printing
+// errors building the tests.)
+//
+// Go test runs in two different modes:
+//
+// The first, called local directory mode, occurs when go test is
+// invoked with no package arguments (for example, 'go test' or 'go
+// test -v'). In this mode, go test compiles the package sources and
+// tests found in the current directory and then runs the resulting
+// test binary. In this mode, caching (discussed below) is disabled.
+// After the package test finishes, go test prints a summary line
+// showing the test status ('ok' or 'FAIL'), package name, and elapsed
+// time.
+//
+// The second, called package list mode, occurs when go test is invoked
+// with explicit package arguments (for example 'go test math', 'go
+// test ./...', and even 'go test .'). In this mode, go test compiles
+// and tests each of the packages listed on the command line. If a
+// package test passes, go test prints only the final 'ok' summary
+// line. If a package test fails, go test prints the full test output.
+// If invoked with the -bench or -v flag, go test prints the full
+// output even for passing package tests, in order to display the
 // requested benchmark results or verbose logging.
 //
-// All test output and summary lines are printed to the go command's standard
-// output, even if the test printed them to its own standard error.
-// (The go command's standard error is reserved for printing errors building
-// the tests.)
-//
-// In package list mode, go test also caches successful package test results.
-// If go test has cached a previous test run using the same test binary and
-// the same command line consisting entirely of cacheable test flags
-// (defined as -cpu, -list, -parallel, -run, -short, and -v),
-// go test will redisplay the previous output instead of running the test
-// binary again. In the summary line, go test prints '(cached)' in place of
-// the elapsed time. To disable test caching, use any test flag or argument
-// other than the cacheable flags. The idiomatic way to disable test caching
-// explicitly is to use -count=1. A cached result is treated as executing in
-// no time at all, so a successful package test result will be cached and reused
+// In package list mode only, go test caches successful package test
+// results to avoid unnecessary repeated running of tests. When the
+// result of a test can be recovered from the cache, go test will
+// redisplay the previous output instead of running the test binary
+// again. When this happens, go test prints '(cached)' in place of the
+// elapsed time in the summary line.
+//
+// The rule for a match in the cache is that the run involves the same
+// test binary and the flags on the command line come entirely from a
+// restricted set of 'cacheable' test flags, defined as -cpu, -list,
+// -parallel, -run, -short, and -v. If a run of go test has any test
+// or non-test flags outside this set, the result is not cached. To
+// disable test caching, use any test flag or argument other than the
+// cacheable flags. The idiomatic way to disable test caching explicitly
+// is to use -count=1. Tests that open files within the package's source
+// root (usually $GOPATH) or that consult environment variables only
+// match future runs in which the files and environment variables are unchanged.
+// A cached test result is treated as executing in no time at all,
+// so a successful package test result will be cached and reused
 // regardless of -timeout setting.
 //
 // In addition to the build flags, the flags handled by 'go test' itself are:
@@ -893,7 +906,7 @@
 // the C or C++ compiler, respectively, to use.
 //
 //
-// Description of build modes
+// Build modes
 //
 // The 'go build' and 'go install' commands take a -buildmode argument which
 // indicates which kind of object file is to be built. Currently supported values
@@ -939,6 +952,45 @@
 // 		import, into a Go plugin. Packages not named main are ignored.
 //
 //
+// Build and test caching
+//
+// The go command caches build outputs for reuse in future builds.
+// The default location for cache data is a subdirectory named go-build
+// in the standard user cache directory for the current operating system.
+// Setting the GOCACHE environment variable overrides this default,
+// and running 'go env GOCACHE' prints the current cache directory.
+//
+// The go command periodically deletes cached data that has not been
+// used recently. Running 'go clean -cache' deletes all cached data.
+//
+// The build cache correctly accounts for changes to Go source files,
+// compilers, compiler options, and so on: cleaning the cache explicitly
+// should not be necessary in typical use. However, the build cache
+// does not detect changes to C libraries imported with cgo.
+// If you have made changes to the C libraries on your system, you
+// will need to clean the cache explicitly or else use the -a build flag
+// (see 'go help build') to force rebuilding of packages that
+// depend on the updated C libraries.
+//
+// The go command also caches successful package test results.
+// See 'go help test' for details. Running 'go clean -testcache' removes
+// all cached test results (but not cached build results).
+//
+// The GODEBUG environment variable can enable printing of debugging
+// information about the state of the cache:
+//
+// GODEBUG=gocacheverify=1 causes the go command to bypass the
+// use of any cache entries and instead rebuild everything and check
+// that the results match existing cache entries.
+//
+// GODEBUG=gocachehash=1 causes the go command to print the inputs
+// for all of the content hashes it uses to construct cache lookup keys.
+// The output is voluminous but can be useful for debugging the cache.
+//
+// GODEBUG=gocachetest=1 causes the go command to print details of its
+// decisions about whether to reuse a cached test result.
+//
+//
 // File types
 //
 // The go command examines the contents of a restricted set of files
@@ -1396,7 +1448,7 @@
 // See https://golang.org/s/go14customimport for details.
 //
 //
-// Description of package lists
+// Package lists
 //
 // Many commands apply to a set of packages:
 //
@@ -1478,7 +1530,7 @@
 // by the go tool, as are directories named "testdata".
 //
 //
-// Description of testing flags
+// Testing flags
 //
 // The 'go test' command takes both flags that apply to 'go test' itself
 // and flags that apply to the resulting test binary.
@@ -1705,7 +1757,7 @@
 // binary, instead of being interpreted as the package list.
 //
 //
-// Description of testing functions
+// Testing functions
 //
 // The 'go test' command expects to find test, benchmark, and example functions
 // in the "*_test.go" files corresponding to the package under test.
diff --git a/libgo/go/cmd/go/go_test.go b/libgo/go/cmd/go/go_test.go
index 7276a2c..41a37a5 100644
--- a/libgo/go/cmd/go/go_test.go
+++ b/libgo/go/cmd/go/go_test.go
@@ -2461,6 +2461,17 @@ func TestCoverageRuns(t *testing.T) {
 	checkCoverage(tg, data)
 }
 
+func TestCoverageDotImport(t *testing.T) {
+	skipIfGccgo(t, "gccgo has no cover tool")
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
+	tg.run("test", "-coverpkg=coverdot1,coverdot2", "coverdot2")
+	data := tg.getStdout() + tg.getStderr()
+	checkCoverage(tg, data)
+}
+
 // Check that coverage analysis uses set mode.
 // Also check that coverage profiles merge correctly.
 func TestCoverageUsesSetMode(t *testing.T) {
@@ -3243,6 +3254,16 @@ func TestGoVetWithFlagsOff(t *testing.T) {
 	tg.run("vet", "-printf=false", "vetpkg")
 }
 
+// Issue 23395.
+func TestGoVetWithOnlyTestFiles(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+	tg.tempFile("src/p/p_test.go", "package p; import \"testing\"; func TestMe(*testing.T) {}")
+	tg.setenv("GOPATH", tg.path("."))
+	tg.run("vet", "p")
+}
+
 // Issue 9767, 19769.
 func TestGoGetDotSlashDownload(t *testing.T) {
 	testenv.MustHaveExternalNetwork(t)
diff --git a/libgo/go/cmd/go/internal/cache/default.go b/libgo/go/cmd/go/internal/cache/default.go
index 8a5c12c..8285f78 100644
--- a/libgo/go/cmd/go/internal/cache/default.go
+++ b/libgo/go/cmd/go/internal/cache/default.go
@@ -69,6 +69,11 @@ func DefaultDir() string {
 	case "windows":
 		dir = os.Getenv("LocalAppData")
 		if dir == "" {
+			// Fall back to %AppData%, the old name of
+			// %LocalAppData% on Windows XP.
+			dir = os.Getenv("AppData")
+		}
+		if dir == "" {
 			return "off"
 		}
 
diff --git a/libgo/go/cmd/go/internal/help/helpdoc.go b/libgo/go/cmd/go/internal/help/helpdoc.go
index 6dcba37..126e866 100644
--- a/libgo/go/cmd/go/internal/help/helpdoc.go
+++ b/libgo/go/cmd/go/internal/help/helpdoc.go
@@ -30,7 +30,7 @@ the C or C++ compiler, respectively, to use.
 
 var HelpPackages = &base.Command{
 	UsageLine: "packages",
-	Short:     "description of package lists",
+	Short:     "package lists",
 	Long: `
 Many commands apply to a set of packages:
 
@@ -586,7 +586,7 @@ command.
 
 var HelpBuildmode = &base.Command{
 	UsageLine: "buildmode",
-	Short:     "description of build modes",
+	Short:     "build modes",
 	Long: `
 The 'go build' and 'go install' commands take a -buildmode argument which
 indicates which kind of object file is to be built. Currently supported values
@@ -632,3 +632,45 @@ are:
 		import, into a Go plugin. Packages not named main are ignored.
 `,
 }
+
+var HelpCache = &base.Command{
+	UsageLine: "cache",
+	Short:     "build and test caching",
+	Long: `
+The go command caches build outputs for reuse in future builds.
+The default location for cache data is a subdirectory named go-build
+in the standard user cache directory for the current operating system.
+Setting the GOCACHE environment variable overrides this default,
+and running 'go env GOCACHE' prints the current cache directory.
+
+The go command periodically deletes cached data that has not been
+used recently. Running 'go clean -cache' deletes all cached data.
+
+The build cache correctly accounts for changes to Go source files,
+compilers, compiler options, and so on: cleaning the cache explicitly
+should not be necessary in typical use. However, the build cache
+does not detect changes to C libraries imported with cgo.
+If you have made changes to the C libraries on your system, you
+will need to clean the cache explicitly or else use the -a build flag
+(see 'go help build') to force rebuilding of packages that
+depend on the updated C libraries.
+
+The go command also caches successful package test results.
+See 'go help test' for details. Running 'go clean -testcache' removes
+all cached test results (but not cached build results).
+
+The GODEBUG environment variable can enable printing of debugging
+information about the state of the cache:
+
+GODEBUG=gocacheverify=1 causes the go command to bypass the
+use of any cache entries and instead rebuild everything and check
+that the results match existing cache entries.
+
+GODEBUG=gocachehash=1 causes the go command to print the inputs
+for all of the content hashes it uses to construct cache lookup keys.
+The output is voluminous but can be useful for debugging the cache.
+
+GODEBUG=gocachetest=1 causes the go command to print details of its
+decisions about whether to reuse a cached test result.
+`,
+}
diff --git a/libgo/go/cmd/go/internal/load/pkg.go b/libgo/go/cmd/go/internal/load/pkg.go
index 20e905c..609a47d 100644
--- a/libgo/go/cmd/go/internal/load/pkg.go
+++ b/libgo/go/cmd/go/internal/load/pkg.go
@@ -1526,3 +1526,153 @@ func GoFilesPackage(gofiles []string) *Package {
 
 	return pkg
 }
+
+// GetTestPackagesFor returns package structs ptest, the package p plus
+// its test files, and pxtest, the external tests of package p.
+// pxtest may be nil. If there are no test files, forceTest decides
+// whether this returns a new package struct or just returns p.
+func GetTestPackagesFor(p *Package, forceTest bool) (ptest, pxtest *Package, err error) {
+	var imports, ximports []*Package
+	var stk ImportStack
+	stk.Push(p.ImportPath + " (test)")
+	rawTestImports := str.StringList(p.TestImports)
+	for i, path := range p.TestImports {
+		p1 := LoadImport(path, p.Dir, p, &stk, p.Internal.Build.TestImportPos[path], UseVendor)
+		if cfg.BuildToolchainName == "gccgo" && p1.Standard {
+			continue
+		}
+		if p1.Error != nil {
+			return nil, nil, p1.Error
+		}
+		if len(p1.DepsErrors) > 0 {
+			err := p1.DepsErrors[0]
+			err.Pos = "" // show full import stack
+			return nil, nil, err
+		}
+		if str.Contains(p1.Deps, p.ImportPath) || p1.ImportPath == p.ImportPath {
+			// Same error that loadPackage returns (via reusePackage) in pkg.go.
+			// Can't change that code, because that code is only for loading the
+			// non-test copy of a package.
+			err := &PackageError{
+				ImportStack:   testImportStack(stk[0], p1, p.ImportPath),
+				Err:           "import cycle not allowed in test",
+				IsImportCycle: true,
+			}
+			return nil, nil, err
+		}
+		p.TestImports[i] = p1.ImportPath
+		imports = append(imports, p1)
+	}
+	stk.Pop()
+	stk.Push(p.ImportPath + "_test")
+	pxtestNeedsPtest := false
+	rawXTestImports := str.StringList(p.XTestImports)
+	for i, path := range p.XTestImports {
+		p1 := LoadImport(path, p.Dir, p, &stk, p.Internal.Build.XTestImportPos[path], UseVendor)
+		if cfg.BuildToolchainName == "gccgo" && p1.Standard {
+			continue
+		}
+		if p1.Error != nil {
+			return nil, nil, p1.Error
+		}
+		if len(p1.DepsErrors) > 0 {
+			err := p1.DepsErrors[0]
+			err.Pos = "" // show full import stack
+			return nil, nil, err
+		}
+		if p1.ImportPath == p.ImportPath {
+			pxtestNeedsPtest = true
+		} else {
+			ximports = append(ximports, p1)
+		}
+		p.XTestImports[i] = p1.ImportPath
+	}
+	stk.Pop()
+
+	// Test package.
+	if len(p.TestGoFiles) > 0 || forceTest {
+		ptest = new(Package)
+		*ptest = *p
+		ptest.GoFiles = nil
+		ptest.GoFiles = append(ptest.GoFiles, p.GoFiles...)
+		ptest.GoFiles = append(ptest.GoFiles, p.TestGoFiles...)
+		ptest.Target = ""
+		// Note: The preparation of the vet config requires that common
+		// indexes in ptest.Imports, ptest.Internal.Imports, and ptest.Internal.RawImports
+		// all line up (but RawImports can be shorter than the others).
+		// That is, for 0 ≤ i < len(RawImports),
+		// RawImports[i] is the import string in the program text,
+		// Imports[i] is the expanded import string (vendoring applied or relative path expanded away),
+		// and Internal.Imports[i] is the corresponding *Package.
+		// Any implicitly added imports appear in Imports and Internal.Imports
+		// but not RawImports (because they were not in the source code).
+		// We insert TestImports, imports, and rawTestImports at the start of
+		// these lists to preserve the alignment.
+		ptest.Imports = str.StringList(p.TestImports, p.Imports)
+		ptest.Internal.Imports = append(imports, p.Internal.Imports...)
+		ptest.Internal.RawImports = str.StringList(rawTestImports, p.Internal.RawImports)
+		ptest.Internal.ForceLibrary = true
+		ptest.Internal.Build = new(build.Package)
+		*ptest.Internal.Build = *p.Internal.Build
+		m := map[string][]token.Position{}
+		for k, v := range p.Internal.Build.ImportPos {
+			m[k] = append(m[k], v...)
+		}
+		for k, v := range p.Internal.Build.TestImportPos {
+			m[k] = append(m[k], v...)
+		}
+		ptest.Internal.Build.ImportPos = m
+	} else {
+		ptest = p
+	}
+
+	// External test package.
+	if len(p.XTestGoFiles) > 0 {
+		pxtest = &Package{
+			PackagePublic: PackagePublic{
+				Name:       p.Name + "_test",
+				ImportPath: p.ImportPath + "_test",
+				Root:       p.Root,
+				Dir:        p.Dir,
+				GoFiles:    p.XTestGoFiles,
+				Imports:    p.XTestImports,
+			},
+			Internal: PackageInternal{
+				LocalPrefix: p.Internal.LocalPrefix,
+				Build: &build.Package{
+					ImportPos: p.Internal.Build.XTestImportPos,
+				},
+				Imports:    ximports,
+				RawImports: rawXTestImports,
+
+				Asmflags:   p.Internal.Asmflags,
+				Gcflags:    p.Internal.Gcflags,
+				Ldflags:    p.Internal.Ldflags,
+				Gccgoflags: p.Internal.Gccgoflags,
+			},
+		}
+		if pxtestNeedsPtest {
+			pxtest.Internal.Imports = append(pxtest.Internal.Imports, ptest)
+		}
+	}
+
+	return ptest, pxtest, nil
+}
+
+func testImportStack(top string, p *Package, target string) []string {
+	stk := []string{top, p.ImportPath}
+Search:
+	for p.ImportPath != target {
+		for _, p1 := range p.Internal.Imports {
+			if p1.ImportPath == target || str.Contains(p1.Deps, target) {
+				stk = append(stk, p1.ImportPath)
+				p = p1
+				continue Search
+			}
+		}
+		// Can't happen, but in case it does...
+		stk = append(stk, "<lost path to cycle>")
+		break
+	}
+	return stk
+}
diff --git a/libgo/go/cmd/go/internal/test/test.go b/libgo/go/cmd/go/internal/test/test.go
index b82fdd5..e77e834 100644
--- a/libgo/go/cmd/go/internal/test/test.go
+++ b/libgo/go/cmd/go/internal/test/test.go
@@ -6,6 +6,7 @@ package test
 
 import (
 	"bytes"
+	"crypto/sha256"
 	"errors"
 	"fmt"
 	"go/ast"
@@ -79,39 +80,51 @@ finds any problems, go test reports those and does not run the test binary.
 Only a high-confidence subset of the default go vet checks are used.
 To disable the running of go vet, use the -vet=off flag.
 
-Go test runs in two different modes: local directory mode when invoked with
-no package arguments (for example, 'go test'), and package list mode when
-invoked with package arguments (for example 'go test math', 'go test ./...',
-and even 'go test .').
-
-In local directory mode, go test compiles and tests the package sources
-found in the current directory and then runs the resulting test binary.
-In this mode, caching (discussed below) is disabled. After the package test
-finishes, go test prints a summary line showing the test status ('ok' or 'FAIL'),
-package name, and elapsed time.
-
-In package list mode, go test compiles and tests each of the packages
-listed on the command line. If a package test passes, go test prints only
-the final 'ok' summary line. If a package test fails, go test prints the
-full test output. If invoked with the -bench or -v flag, go test prints
-the full output even for passing package tests, in order to display the
+All test output and summary lines are printed to the go command's
+standard output, even if the test printed them to its own standard
+error. (The go command's standard error is reserved for printing
+errors building the tests.)
+
+Go test runs in two different modes:
+
+The first, called local directory mode, occurs when go test is
+invoked with no package arguments (for example, 'go test' or 'go
+test -v'). In this mode, go test compiles the package sources and
+tests found in the current directory and then runs the resulting
+test binary. In this mode, caching (discussed below) is disabled.
+After the package test finishes, go test prints a summary line
+showing the test status ('ok' or 'FAIL'), package name, and elapsed
+time.
+
+The second, called package list mode, occurs when go test is invoked
+with explicit package arguments (for example 'go test math', 'go
+test ./...', and even 'go test .'). In this mode, go test compiles
+and tests each of the packages listed on the command line. If a
+package test passes, go test prints only the final 'ok' summary
+line. If a package test fails, go test prints the full test output.
+If invoked with the -bench or -v flag, go test prints the full
+output even for passing package tests, in order to display the
 requested benchmark results or verbose logging.
 
-All test output and summary lines are printed to the go command's standard
-output, even if the test printed them to its own standard error.
-(The go command's standard error is reserved for printing errors building
-the tests.)
-
-In package list mode, go test also caches successful package test results.
-If go test has cached a previous test run using the same test binary and
-the same command line consisting entirely of cacheable test flags
-(defined as -cpu, -list, -parallel, -run, -short, and -v),
-go test will redisplay the previous output instead of running the test
-binary again. In the summary line, go test prints '(cached)' in place of
-the elapsed time. To disable test caching, use any test flag or argument
-other than the cacheable flags. The idiomatic way to disable test caching
-explicitly is to use -count=1. A cached result is treated as executing in
-no time at all, so a successful package test result will be cached and reused
+In package list mode only, go test caches successful package test
+results to avoid unnecessary repeated running of tests. When the
+result of a test can be recovered from the cache, go test will
+redisplay the previous output instead of running the test binary
+again. When this happens, go test prints '(cached)' in place of the
+elapsed time in the summary line.
+
+The rule for a match in the cache is that the run involves the same
+test binary and the flags on the command line come entirely from a
+restricted set of 'cacheable' test flags, defined as -cpu, -list,
+-parallel, -run, -short, and -v. If a run of go test has any test
+or non-test flags outside this set, the result is not cached. To
+disable test caching, use any test flag or argument other than the
+cacheable flags. The idiomatic way to disable test caching explicitly
+is to use -count=1. Tests that open files within the package's source
+root (usually $GOPATH) or that consult environment variables only
+match future runs in which the files and environment variables are unchanged.
+A cached test result is treated as executing in no time at all,
+so a successful package test result will be cached and reused
 regardless of -timeout setting.
 
 ` + strings.TrimSpace(testFlag1) + ` See 'go help testflag' for details.
@@ -167,7 +180,7 @@ func Usage() {
 
 var HelpTestflag = &base.Command{
 	UsageLine: "testflag",
-	Short:     "description of testing flags",
+	Short:     "testing flags",
 	Long: `
 The 'go test' command takes both flags that apply to 'go test' itself
 and flags that apply to the resulting test binary.
@@ -401,7 +414,7 @@ binary, instead of being interpreted as the package list.
 
 var HelpTestfunc = &base.Command{
 	UsageLine: "testfunc",
-	Short:     "description of testing functions",
+	Short:     "testing functions",
 	Long: `
 The 'go test' command expects to find test, benchmark, and example functions
 in the "*_test.go" files corresponding to the package under test.
@@ -771,62 +784,12 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 	//	pmain - pkg.test binary
 	var ptest, pxtest, pmain *load.Package
 
-	var imports, ximports []*load.Package
-	var stk load.ImportStack
-	stk.Push(p.ImportPath + " (test)")
-	rawTestImports := str.StringList(p.TestImports)
-	for i, path := range p.TestImports {
-		p1 := load.LoadImport(path, p.Dir, p, &stk, p.Internal.Build.TestImportPos[path], load.UseVendor)
-		if cfg.BuildToolchainName == "gccgo" && p1.Standard {
-			continue
-		}
-		if p1.Error != nil {
-			return nil, nil, nil, p1.Error
-		}
-		if len(p1.DepsErrors) > 0 {
-			err := p1.DepsErrors[0]
-			err.Pos = "" // show full import stack
-			return nil, nil, nil, err
-		}
-		if str.Contains(p1.Deps, p.ImportPath) || p1.ImportPath == p.ImportPath {
-			// Same error that loadPackage returns (via reusePackage) in pkg.go.
-			// Can't change that code, because that code is only for loading the
-			// non-test copy of a package.
-			err := &load.PackageError{
-				ImportStack:   testImportStack(stk[0], p1, p.ImportPath),
-				Err:           "import cycle not allowed in test",
-				IsImportCycle: true,
-			}
-			return nil, nil, nil, err
-		}
-		p.TestImports[i] = p1.ImportPath
-		imports = append(imports, p1)
-	}
-	stk.Pop()
-	stk.Push(p.ImportPath + "_test")
-	pxtestNeedsPtest := false
-	rawXTestImports := str.StringList(p.XTestImports)
-	for i, path := range p.XTestImports {
-		p1 := load.LoadImport(path, p.Dir, p, &stk, p.Internal.Build.XTestImportPos[path], load.UseVendor)
-		if cfg.BuildToolchainName == "gccgo" && p1.Standard {
-			continue
-		}
-		if p1.Error != nil {
-			return nil, nil, nil, p1.Error
-		}
-		if len(p1.DepsErrors) > 0 {
-			err := p1.DepsErrors[0]
-			err.Pos = "" // show full import stack
-			return nil, nil, nil, err
-		}
-		if p1.ImportPath == p.ImportPath {
-			pxtestNeedsPtest = true
-		} else {
-			ximports = append(ximports, p1)
-		}
-		p.XTestImports[i] = p1.ImportPath
+	localCover := testCover && testCoverPaths == nil
+
+	ptest, pxtest, err = load.GetTestPackagesFor(p, localCover || p.Name == "main")
+	if err != nil {
+		return nil, nil, nil, err
 	}
-	stk.Pop()
 
 	// Use last element of import path, not package name.
 	// They differ when package name is "main".
@@ -844,81 +807,12 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 	// only for this package and only for this test?
 	// Yes, if -cover is on but -coverpkg has not specified
 	// a list of packages for global coverage.
-	localCover := testCover && testCoverPaths == nil
-
-	// Test package.
-	if len(p.TestGoFiles) > 0 || localCover || p.Name == "main" {
-		ptest = new(load.Package)
-		*ptest = *p
-		ptest.GoFiles = nil
-		ptest.GoFiles = append(ptest.GoFiles, p.GoFiles...)
-		ptest.GoFiles = append(ptest.GoFiles, p.TestGoFiles...)
-		ptest.Target = ""
-		// Note: The preparation of the vet config requires that common
-		// indexes in ptest.Imports, ptest.Internal.Imports, and ptest.Internal.RawImports
-		// all line up (but RawImports can be shorter than the others).
-		// That is, for 0 ≤ i < len(RawImports),
-		// RawImports[i] is the import string in the program text,
-		// Imports[i] is the expanded import string (vendoring applied or relative path expanded away),
-		// and Internal.Imports[i] is the corresponding *Package.
-		// Any implicitly added imports appear in Imports and Internal.Imports
-		// but not RawImports (because they were not in the source code).
-		// We insert TestImports, imports, and rawTestImports at the start of
-		// these lists to preserve the alignment.
-		ptest.Imports = str.StringList(p.TestImports, p.Imports)
-		ptest.Internal.Imports = append(imports, p.Internal.Imports...)
-		ptest.Internal.RawImports = str.StringList(rawTestImports, p.Internal.RawImports)
-		ptest.Internal.ForceLibrary = true
-		ptest.Internal.Build = new(build.Package)
-		*ptest.Internal.Build = *p.Internal.Build
-		m := map[string][]token.Position{}
-		for k, v := range p.Internal.Build.ImportPos {
-			m[k] = append(m[k], v...)
-		}
-		for k, v := range p.Internal.Build.TestImportPos {
-			m[k] = append(m[k], v...)
-		}
-		ptest.Internal.Build.ImportPos = m
-
-		if localCover {
-			ptest.Internal.CoverMode = testCoverMode
-			var coverFiles []string
-			coverFiles = append(coverFiles, ptest.GoFiles...)
-			coverFiles = append(coverFiles, ptest.CgoFiles...)
-			ptest.Internal.CoverVars = declareCoverVars(ptest.ImportPath, coverFiles...)
-		}
-	} else {
-		ptest = p
-	}
-
-	// External test package.
-	if len(p.XTestGoFiles) > 0 {
-		pxtest = &load.Package{
-			PackagePublic: load.PackagePublic{
-				Name:       p.Name + "_test",
-				ImportPath: p.ImportPath + "_test",
-				Root:       p.Root,
-				Dir:        p.Dir,
-				GoFiles:    p.XTestGoFiles,
-				Imports:    p.XTestImports,
-			},
-			Internal: load.PackageInternal{
-				LocalPrefix: p.Internal.LocalPrefix,
-				Build: &build.Package{
-					ImportPos: p.Internal.Build.XTestImportPos,
-				},
-				Imports:    ximports,
-				RawImports: rawXTestImports,
-
-				Asmflags:   p.Internal.Asmflags,
-				Gcflags:    p.Internal.Gcflags,
-				Ldflags:    p.Internal.Ldflags,
-				Gccgoflags: p.Internal.Gccgoflags,
-			},
-		}
-		if pxtestNeedsPtest {
-			pxtest.Internal.Imports = append(pxtest.Internal.Imports, ptest)
-		}
+	if localCover {
+		ptest.Internal.CoverMode = testCoverMode
+		var coverFiles []string
+		coverFiles = append(coverFiles, ptest.GoFiles...)
+		coverFiles = append(coverFiles, ptest.CgoFiles...)
+		ptest.Internal.CoverVars = declareCoverVars(ptest.ImportPath, coverFiles...)
 	}
 
 	testDir := b.NewObjdir()
@@ -948,6 +842,7 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 
 	// The generated main also imports testing, regexp, and os.
 	// Also the linker introduces implicit dependencies reported by LinkerDeps.
+	var stk load.ImportStack
 	stk.Push("testmain")
 	deps := testMainDeps // cap==len, so safe for append
 	for _, d := range load.LinkerDeps(p) {
@@ -1153,24 +1048,6 @@ func addTestVet(b *work.Builder, p *load.Package, runAction, installAction *work
 	}
 }
 
-func testImportStack(top string, p *load.Package, target string) []string {
-	stk := []string{top, p.ImportPath}
-Search:
-	for p.ImportPath != target {
-		for _, p1 := range p.Internal.Imports {
-			if p1.ImportPath == target || str.Contains(p1.Deps, target) {
-				stk = append(stk, p1.ImportPath)
-				p = p1
-				continue Search
-			}
-		}
-		// Can't happen, but in case it does...
-		stk = append(stk, "<lost path to cycle>")
-		break
-	}
-	return stk
-}
-
 func recompileForTest(pmain, preal, ptest, pxtest *load.Package) {
 	// The "test copy" of preal is ptest.
 	// For each package that depends on preal, make a "test copy"
@@ -1221,13 +1098,21 @@ func isTestFile(file string) bool {
 func declareCoverVars(importPath string, files ...string) map[string]*load.CoverVar {
 	coverVars := make(map[string]*load.CoverVar)
 	coverIndex := 0
+	// We create the cover counters as new top-level variables in the package.
+	// We need to avoid collisions with user variables (GoCover_0 is unlikely but still)
+	// and more importantly with dot imports of other covered packages,
+	// so we append 12 hex digits from the SHA-256 of the import path.
+	// The point is only to avoid accidents, not to defeat users determined to
+	// break things.
+	sum := sha256.Sum256([]byte(importPath))
+	h := fmt.Sprintf("%x", sum[:6])
 	for _, file := range files {
 		if isTestFile(file) {
 			continue
 		}
 		coverVars[file] = &load.CoverVar{
 			File: filepath.Join(importPath, file),
-			Var:  fmt.Sprintf("GoCover_%d", coverIndex),
+			Var:  fmt.Sprintf("GoCover_%d_%x", coverIndex, h),
 		}
 		coverIndex++
 	}
diff --git a/libgo/go/cmd/go/internal/vet/vet.go b/libgo/go/cmd/go/internal/vet/vet.go
index 8b4f926..07eed89 100644
--- a/libgo/go/cmd/go/internal/vet/vet.go
+++ b/libgo/go/cmd/go/internal/vet/vet.go
@@ -57,7 +57,21 @@ func runVet(cmd *base.Command, args []string) {
 
 	root := &work.Action{Mode: "go vet"}
 	for _, p := range pkgs {
-		root.Deps = append(root.Deps, b.VetAction(work.ModeBuild, work.ModeBuild, p))
+		ptest, pxtest, err := load.GetTestPackagesFor(p, false)
+		if err != nil {
+			base.Errorf("%v", err)
+			continue
+		}
+		if len(ptest.GoFiles) == 0 && pxtest == nil {
+			base.Errorf("go vet %s: no Go files in %s", p.ImportPath, p.Dir)
+			continue
+		}
+		if len(ptest.GoFiles) > 0 {
+			root.Deps = append(root.Deps, b.VetAction(work.ModeBuild, work.ModeBuild, ptest))
+		}
+		if pxtest != nil {
+			root.Deps = append(root.Deps, b.VetAction(work.ModeBuild, work.ModeBuild, pxtest))
+		}
 	}
 	b.Do(root)
 }
diff --git a/libgo/go/cmd/go/internal/work/action.go b/libgo/go/cmd/go/internal/work/action.go
index e7a0c77..803a6bd 100644
--- a/libgo/go/cmd/go/internal/work/action.go
+++ b/libgo/go/cmd/go/internal/work/action.go
@@ -652,11 +652,9 @@ func (b *Builder) linkSharedAction(mode, depMode BuildMode, shlib string, a1 *Ac
 		// it is not present in another shared library, add it here.
 		// TODO(rsc): Maybe this should only happen if "runtime" is in the original package set.
 		// TODO(rsc): This should probably be changed to use load.LinkerDeps(p).
-		// TODO(rsc): Find out and explain here why gccgo is excluded.
-		// If the answer is that gccgo is different in implicit linker deps, maybe
-		// load.LinkerDeps should be used and updated.
-		// Link packages into a shared library.
-
+		// TODO(rsc): We don't add standard library imports for gccgo
+		// because they are all always linked in anyhow.
+		// Maybe load.LinkerDeps should be used and updated.
 		a := &Action{
 			Mode:    "go build -buildmode=shared",
 			Package: p,
diff --git a/libgo/go/cmd/go/internal/work/exec.go b/libgo/go/cmd/go/internal/work/exec.go
index edd2694..b587498 100644
--- a/libgo/go/cmd/go/internal/work/exec.go
+++ b/libgo/go/cmd/go/internal/work/exec.go
@@ -308,7 +308,7 @@ func (b *Builder) build(a *Action) (err error) {
 			// Need to look for install header actions depending on this action,
 			// or depending on a link that depends on this action.
 			needHeader := false
-			if (a.Package.UsesCgo() || a.Package.UsesSwig()) && (cfg.BuildBuildmode == "c-archive" || cfg.BuildBuildmode == "c-header") {
+			if (a.Package.UsesCgo() || a.Package.UsesSwig()) && (cfg.BuildBuildmode == "c-archive" || cfg.BuildBuildmode == "c-shared") {
 				for _, t1 := range a.triggers {
 					if t1.Mode == "install header" {
 						needHeader = true
diff --git a/libgo/go/cmd/go/internal/work/gccgo.go b/libgo/go/cmd/go/internal/work/gccgo.go
index dcb38af..8f55846 100644
--- a/libgo/go/cmd/go/internal/work/gccgo.go
+++ b/libgo/go/cmd/go/internal/work/gccgo.go
@@ -206,7 +206,6 @@ func (gccgoToolchain) pack(b *Builder, a *Action, afile string, ofiles []string)
 func (tools gccgoToolchain) link(b *Builder, root *Action, out, importcfg string, allactions []*Action, buildmode, desc string) error {
 	// gccgo needs explicit linking with all package dependencies,
 	// and all LDFLAGS from cgo dependencies.
-	apackagePathsSeen := make(map[string]bool)
 	afiles := []string{}
 	shlibs := []string{}
 	ldflags := b.gccArchArgs()
@@ -294,56 +293,57 @@ func (tools gccgoToolchain) link(b *Builder, root *Action, out, importcfg string
 		return newArchive, nil
 	}
 
-	actionsSeen := make(map[*Action]bool)
-	// Make a pre-order depth-first traversal of the action graph, taking note of
-	// whether a shared library action has been seen on the way to an action (the
-	// construction of the graph means that if any path to a node passes through
-	// a shared library action, they all do).
-	var walk func(a *Action, seenShlib bool)
-	var err error
-	walk = func(a *Action, seenShlib bool) {
-		if actionsSeen[a] {
-			return
-		}
-		actionsSeen[a] = true
-		if a.Package != nil && !seenShlib {
-			if a.Package.Standard {
-				return
+	// If using -linkshared, find the shared library deps.
+	haveShlib := make(map[string]bool)
+	targetBase := filepath.Base(root.Target)
+	if cfg.BuildLinkshared {
+		for _, a := range root.Deps {
+			p := a.Package
+			if p == nil || p.Shlib == "" {
+				continue
 			}
-			// We record the target of the first time we see a .a file
-			// for a package to make sure that we prefer the 'install'
-			// rather than the 'build' location (which may not exist any
-			// more). We still need to traverse the dependencies of the
-			// build action though so saying
-			// if apackagePathsSeen[a.Package.ImportPath] { return }
-			// doesn't work.
-			if !apackagePathsSeen[a.Package.ImportPath] {
-				apackagePathsSeen[a.Package.ImportPath] = true
-				target := a.built
-				if len(a.Package.CgoFiles) > 0 || a.Package.UsesSwig() {
-					target, err = readAndRemoveCgoFlags(target)
-					if err != nil {
-						return
-					}
-				}
-				afiles = append(afiles, target)
+
+			// The .a we are linking into this .so
+			// will have its Shlib set to this .so.
+			// Don't start thinking we want to link
+			// this .so into itself.
+			base := filepath.Base(p.Shlib)
+			if base != targetBase {
+				haveShlib[base] = true
 			}
 		}
-		if strings.HasSuffix(a.Target, ".so") {
-			shlibs = append(shlibs, a.Target)
-			seenShlib = true
+	}
+
+	// Arrange the deps into afiles and shlibs.
+	addedShlib := make(map[string]bool)
+	for _, a := range root.Deps {
+		p := a.Package
+		if p != nil && p.Shlib != "" && haveShlib[filepath.Base(p.Shlib)] {
+			// This is a package linked into a shared
+			// library that we will put into shlibs.
+			continue
 		}
-		for _, a1 := range a.Deps {
-			walk(a1, seenShlib)
-			if err != nil {
-				return
+
+		if haveShlib[filepath.Base(a.Target)] {
+			// This is a shared library we want to link againt.
+			if !addedShlib[a.Target] {
+				shlibs = append(shlibs, a.Target)
+				addedShlib[a.Target] = true
 			}
+			continue
 		}
-	}
-	for _, a1 := range root.Deps {
-		walk(a1, false)
-		if err != nil {
-			return err
+
+		if p != nil {
+			target := a.built
+			if p.UsesCgo() || p.UsesSwig() {
+				var err error
+				target, err = readAndRemoveCgoFlags(target)
+				if err != nil {
+					continue
+				}
+			}
+
+			afiles = append(afiles, target)
 		}
 	}
 
@@ -511,9 +511,7 @@ func (tools gccgoToolchain) ld(b *Builder, root *Action, out, importcfg, mainpkg
 }
 
 func (tools gccgoToolchain) ldShared(b *Builder, root *Action, toplevelactions []*Action, out, importcfg string, allactions []*Action) error {
-	fakeRoot := *root
-	fakeRoot.Deps = toplevelactions
-	return tools.link(b, &fakeRoot, out, importcfg, allactions, "shared", out)
+	return tools.link(b, root, out, importcfg, allactions, "shared", out)
 }
 
 func (tools gccgoToolchain) cc(b *Builder, a *Action, ofile, cfile string) error {
diff --git a/libgo/go/cmd/go/main.go b/libgo/go/cmd/go/main.go
index 09147ee..7558e08 100644
--- a/libgo/go/cmd/go/main.go
+++ b/libgo/go/cmd/go/main.go
@@ -56,6 +56,7 @@ func init() {
 
 		help.HelpC,
 		help.HelpBuildmode,
+		help.HelpCache,
 		help.HelpFileType,
 		help.HelpGopath,
 		help.HelpEnvironment,
diff --git a/libgo/go/crypto/x509/verify.go b/libgo/go/crypto/x509/verify.go
index 7a6bd45..9477e85 100644
--- a/libgo/go/crypto/x509/verify.go
+++ b/libgo/go/crypto/x509/verify.go
@@ -781,7 +781,17 @@ func (c *Certificate) isValid(certType int, currentChain []*Certificate, opts *V
 // If opts.Roots is nil and system roots are unavailable the returned error
 // will be of type SystemRootsError.
 //
-// WARNING: this doesn't do any revocation checking.
+// Name constraints in the intermediates will be applied to all names claimed
+// in the chain, not just opts.DNSName. Thus it is invalid for a leaf to claim
+// example.com if an intermediate doesn't permit it, even if example.com is not
+// the name being validated. Note that DirectoryName constraints are not
+// supported.
+//
+// Extended Key Usage values are enforced down a chain, so an intermediate or
+// root that enumerates EKUs prevents a leaf from asserting an EKU not in that
+// list.
+//
+// WARNING: this function doesn't do any revocation checking.
 func (c *Certificate) Verify(opts VerifyOptions) (chains [][]*Certificate, err error) {
 	// Platform-specific verification needs the ASN.1 contents so
 	// this makes the behavior consistent across platforms.
diff --git a/libgo/go/database/sql/convert_test.go b/libgo/go/database/sql/convert_test.go
index 47098c8..b0aff7b 100644
--- a/libgo/go/database/sql/convert_test.go
+++ b/libgo/go/database/sql/convert_test.go
@@ -64,125 +64,128 @@ var (
 	scaniface  interface{}
 )
 
-var conversionTests = []conversionTest{
-	// Exact conversions (destination pointer type matches source type)
-	{s: "foo", d: &scanstr, wantstr: "foo"},
-	{s: 123, d: &scanint, wantint: 123},
-	{s: someTime, d: &scantime, wanttime: someTime},
-
-	// To strings
-	{s: "string", d: &scanstr, wantstr: "string"},
-	{s: []byte("byteslice"), d: &scanstr, wantstr: "byteslice"},
-	{s: 123, d: &scanstr, wantstr: "123"},
-	{s: int8(123), d: &scanstr, wantstr: "123"},
-	{s: int64(123), d: &scanstr, wantstr: "123"},
-	{s: uint8(123), d: &scanstr, wantstr: "123"},
-	{s: uint16(123), d: &scanstr, wantstr: "123"},
-	{s: uint32(123), d: &scanstr, wantstr: "123"},
-	{s: uint64(123), d: &scanstr, wantstr: "123"},
-	{s: 1.5, d: &scanstr, wantstr: "1.5"},
-
-	// From time.Time:
-	{s: time.Unix(1, 0).UTC(), d: &scanstr, wantstr: "1970-01-01T00:00:01Z"},
-	{s: time.Unix(1453874597, 0).In(time.FixedZone("here", -3600*8)), d: &scanstr, wantstr: "2016-01-26T22:03:17-08:00"},
-	{s: time.Unix(1, 2).UTC(), d: &scanstr, wantstr: "1970-01-01T00:00:01.000000002Z"},
-	{s: time.Time{}, d: &scanstr, wantstr: "0001-01-01T00:00:00Z"},
-	{s: time.Unix(1, 2).UTC(), d: &scanbytes, wantbytes: []byte("1970-01-01T00:00:01.000000002Z")},
-	{s: time.Unix(1, 2).UTC(), d: &scaniface, wantiface: time.Unix(1, 2).UTC()},
-
-	// To []byte
-	{s: nil, d: &scanbytes, wantbytes: nil},
-	{s: "string", d: &scanbytes, wantbytes: []byte("string")},
-	{s: []byte("byteslice"), d: &scanbytes, wantbytes: []byte("byteslice")},
-	{s: 123, d: &scanbytes, wantbytes: []byte("123")},
-	{s: int8(123), d: &scanbytes, wantbytes: []byte("123")},
-	{s: int64(123), d: &scanbytes, wantbytes: []byte("123")},
-	{s: uint8(123), d: &scanbytes, wantbytes: []byte("123")},
-	{s: uint16(123), d: &scanbytes, wantbytes: []byte("123")},
-	{s: uint32(123), d: &scanbytes, wantbytes: []byte("123")},
-	{s: uint64(123), d: &scanbytes, wantbytes: []byte("123")},
-	{s: 1.5, d: &scanbytes, wantbytes: []byte("1.5")},
-
-	// To RawBytes
-	{s: nil, d: &scanraw, wantraw: nil},
-	{s: []byte("byteslice"), d: &scanraw, wantraw: RawBytes("byteslice")},
-	{s: "string", d: &scanraw, wantraw: RawBytes("string")},
-	{s: 123, d: &scanraw, wantraw: RawBytes("123")},
-	{s: int8(123), d: &scanraw, wantraw: RawBytes("123")},
-	{s: int64(123), d: &scanraw, wantraw: RawBytes("123")},
-	{s: uint8(123), d: &scanraw, wantraw: RawBytes("123")},
-	{s: uint16(123), d: &scanraw, wantraw: RawBytes("123")},
-	{s: uint32(123), d: &scanraw, wantraw: RawBytes("123")},
-	{s: uint64(123), d: &scanraw, wantraw: RawBytes("123")},
-	{s: 1.5, d: &scanraw, wantraw: RawBytes("1.5")},
-	// time.Time has been placed here to check that the RawBytes slice gets
-	// correctly reset when calling time.Time.AppendFormat.
-	{s: time.Unix(2, 5).UTC(), d: &scanraw, wantraw: RawBytes("1970-01-01T00:00:02.000000005Z")},
-
-	// Strings to integers
-	{s: "255", d: &scanuint8, wantuint: 255},
-	{s: "256", d: &scanuint8, wanterr: "converting driver.Value type string (\"256\") to a uint8: value out of range"},
-	{s: "256", d: &scanuint16, wantuint: 256},
-	{s: "-1", d: &scanint, wantint: -1},
-	{s: "foo", d: &scanint, wanterr: "converting driver.Value type string (\"foo\") to a int: invalid syntax"},
-
-	// int64 to smaller integers
-	{s: int64(5), d: &scanuint8, wantuint: 5},
-	{s: int64(256), d: &scanuint8, wanterr: "converting driver.Value type int64 (\"256\") to a uint8: value out of range"},
-	{s: int64(256), d: &scanuint16, wantuint: 256},
-	{s: int64(65536), d: &scanuint16, wanterr: "converting driver.Value type int64 (\"65536\") to a uint16: value out of range"},
-
-	// True bools
-	{s: true, d: &scanbool, wantbool: true},
-	{s: "True", d: &scanbool, wantbool: true},
-	{s: "TRUE", d: &scanbool, wantbool: true},
-	{s: "1", d: &scanbool, wantbool: true},
-	{s: 1, d: &scanbool, wantbool: true},
-	{s: int64(1), d: &scanbool, wantbool: true},
-	{s: uint16(1), d: &scanbool, wantbool: true},
-
-	// False bools
-	{s: false, d: &scanbool, wantbool: false},
-	{s: "false", d: &scanbool, wantbool: false},
-	{s: "FALSE", d: &scanbool, wantbool: false},
-	{s: "0", d: &scanbool, wantbool: false},
-	{s: 0, d: &scanbool, wantbool: false},
-	{s: int64(0), d: &scanbool, wantbool: false},
-	{s: uint16(0), d: &scanbool, wantbool: false},
-
-	// Not bools
-	{s: "yup", d: &scanbool, wanterr: `sql/driver: couldn't convert "yup" into type bool`},
-	{s: 2, d: &scanbool, wanterr: `sql/driver: couldn't convert 2 into type bool`},
-
-	// Floats
-	{s: float64(1.5), d: &scanf64, wantf64: float64(1.5)},
-	{s: int64(1), d: &scanf64, wantf64: float64(1)},
-	{s: float64(1.5), d: &scanf32, wantf32: float32(1.5)},
-	{s: "1.5", d: &scanf32, wantf32: float32(1.5)},
-	{s: "1.5", d: &scanf64, wantf64: float64(1.5)},
-
-	// Pointers
-	{s: interface{}(nil), d: &scanptr, wantnil: true},
-	{s: int64(42), d: &scanptr, wantptr: &answer},
-
-	// To interface{}
-	{s: float64(1.5), d: &scaniface, wantiface: float64(1.5)},
-	{s: int64(1), d: &scaniface, wantiface: int64(1)},
-	{s: "str", d: &scaniface, wantiface: "str"},
-	{s: []byte("byteslice"), d: &scaniface, wantiface: []byte("byteslice")},
-	{s: true, d: &scaniface, wantiface: true},
-	{s: nil, d: &scaniface},
-	{s: []byte(nil), d: &scaniface, wantiface: []byte(nil)},
-
-	// To a user-defined type
-	{s: 1.5, d: new(userDefined), wantusrdef: 1.5},
-	{s: int64(123), d: new(userDefined), wantusrdef: 123},
-	{s: "1.5", d: new(userDefined), wantusrdef: 1.5},
-	{s: []byte{1, 2, 3}, d: new(userDefinedSlice), wanterr: `unsupported Scan, storing driver.Value type []uint8 into type *sql.userDefinedSlice`},
-	{s: "str", d: new(userDefinedString), wantusrstr: "str"},
-
-	// Other errors
-	{s: complex(1, 2), d: &scanstr, wanterr: `unsupported Scan, storing driver.Value type complex128 into type *string`},
+func conversionTests() []conversionTest {
+	// Return a fresh instance to test so "go test -count 2" works correctly.
+	return []conversionTest{
+		// Exact conversions (destination pointer type matches source type)
+		{s: "foo", d: &scanstr, wantstr: "foo"},
+		{s: 123, d: &scanint, wantint: 123},
+		{s: someTime, d: &scantime, wanttime: someTime},
+
+		// To strings
+		{s: "string", d: &scanstr, wantstr: "string"},
+		{s: []byte("byteslice"), d: &scanstr, wantstr: "byteslice"},
+		{s: 123, d: &scanstr, wantstr: "123"},
+		{s: int8(123), d: &scanstr, wantstr: "123"},
+		{s: int64(123), d: &scanstr, wantstr: "123"},
+		{s: uint8(123), d: &scanstr, wantstr: "123"},
+		{s: uint16(123), d: &scanstr, wantstr: "123"},
+		{s: uint32(123), d: &scanstr, wantstr: "123"},
+		{s: uint64(123), d: &scanstr, wantstr: "123"},
+		{s: 1.5, d: &scanstr, wantstr: "1.5"},
+
+		// From time.Time:
+		{s: time.Unix(1, 0).UTC(), d: &scanstr, wantstr: "1970-01-01T00:00:01Z"},
+		{s: time.Unix(1453874597, 0).In(time.FixedZone("here", -3600*8)), d: &scanstr, wantstr: "2016-01-26T22:03:17-08:00"},
+		{s: time.Unix(1, 2).UTC(), d: &scanstr, wantstr: "1970-01-01T00:00:01.000000002Z"},
+		{s: time.Time{}, d: &scanstr, wantstr: "0001-01-01T00:00:00Z"},
+		{s: time.Unix(1, 2).UTC(), d: &scanbytes, wantbytes: []byte("1970-01-01T00:00:01.000000002Z")},
+		{s: time.Unix(1, 2).UTC(), d: &scaniface, wantiface: time.Unix(1, 2).UTC()},
+
+		// To []byte
+		{s: nil, d: &scanbytes, wantbytes: nil},
+		{s: "string", d: &scanbytes, wantbytes: []byte("string")},
+		{s: []byte("byteslice"), d: &scanbytes, wantbytes: []byte("byteslice")},
+		{s: 123, d: &scanbytes, wantbytes: []byte("123")},
+		{s: int8(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: int64(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint8(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint16(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint32(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: uint64(123), d: &scanbytes, wantbytes: []byte("123")},
+		{s: 1.5, d: &scanbytes, wantbytes: []byte("1.5")},
+
+		// To RawBytes
+		{s: nil, d: &scanraw, wantraw: nil},
+		{s: []byte("byteslice"), d: &scanraw, wantraw: RawBytes("byteslice")},
+		{s: "string", d: &scanraw, wantraw: RawBytes("string")},
+		{s: 123, d: &scanraw, wantraw: RawBytes("123")},
+		{s: int8(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: int64(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint8(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint16(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint32(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: uint64(123), d: &scanraw, wantraw: RawBytes("123")},
+		{s: 1.5, d: &scanraw, wantraw: RawBytes("1.5")},
+		// time.Time has been placed here to check that the RawBytes slice gets
+		// correctly reset when calling time.Time.AppendFormat.
+		{s: time.Unix(2, 5).UTC(), d: &scanraw, wantraw: RawBytes("1970-01-01T00:00:02.000000005Z")},
+
+		// Strings to integers
+		{s: "255", d: &scanuint8, wantuint: 255},
+		{s: "256", d: &scanuint8, wanterr: "converting driver.Value type string (\"256\") to a uint8: value out of range"},
+		{s: "256", d: &scanuint16, wantuint: 256},
+		{s: "-1", d: &scanint, wantint: -1},
+		{s: "foo", d: &scanint, wanterr: "converting driver.Value type string (\"foo\") to a int: invalid syntax"},
+
+		// int64 to smaller integers
+		{s: int64(5), d: &scanuint8, wantuint: 5},
+		{s: int64(256), d: &scanuint8, wanterr: "converting driver.Value type int64 (\"256\") to a uint8: value out of range"},
+		{s: int64(256), d: &scanuint16, wantuint: 256},
+		{s: int64(65536), d: &scanuint16, wanterr: "converting driver.Value type int64 (\"65536\") to a uint16: value out of range"},
+
+		// True bools
+		{s: true, d: &scanbool, wantbool: true},
+		{s: "True", d: &scanbool, wantbool: true},
+		{s: "TRUE", d: &scanbool, wantbool: true},
+		{s: "1", d: &scanbool, wantbool: true},
+		{s: 1, d: &scanbool, wantbool: true},
+		{s: int64(1), d: &scanbool, wantbool: true},
+		{s: uint16(1), d: &scanbool, wantbool: true},
+
+		// False bools
+		{s: false, d: &scanbool, wantbool: false},
+		{s: "false", d: &scanbool, wantbool: false},
+		{s: "FALSE", d: &scanbool, wantbool: false},
+		{s: "0", d: &scanbool, wantbool: false},
+		{s: 0, d: &scanbool, wantbool: false},
+		{s: int64(0), d: &scanbool, wantbool: false},
+		{s: uint16(0), d: &scanbool, wantbool: false},
+
+		// Not bools
+		{s: "yup", d: &scanbool, wanterr: `sql/driver: couldn't convert "yup" into type bool`},
+		{s: 2, d: &scanbool, wanterr: `sql/driver: couldn't convert 2 into type bool`},
+
+		// Floats
+		{s: float64(1.5), d: &scanf64, wantf64: float64(1.5)},
+		{s: int64(1), d: &scanf64, wantf64: float64(1)},
+		{s: float64(1.5), d: &scanf32, wantf32: float32(1.5)},
+		{s: "1.5", d: &scanf32, wantf32: float32(1.5)},
+		{s: "1.5", d: &scanf64, wantf64: float64(1.5)},
+
+		// Pointers
+		{s: interface{}(nil), d: &scanptr, wantnil: true},
+		{s: int64(42), d: &scanptr, wantptr: &answer},
+
+		// To interface{}
+		{s: float64(1.5), d: &scaniface, wantiface: float64(1.5)},
+		{s: int64(1), d: &scaniface, wantiface: int64(1)},
+		{s: "str", d: &scaniface, wantiface: "str"},
+		{s: []byte("byteslice"), d: &scaniface, wantiface: []byte("byteslice")},
+		{s: true, d: &scaniface, wantiface: true},
+		{s: nil, d: &scaniface},
+		{s: []byte(nil), d: &scaniface, wantiface: []byte(nil)},
+
+		// To a user-defined type
+		{s: 1.5, d: new(userDefined), wantusrdef: 1.5},
+		{s: int64(123), d: new(userDefined), wantusrdef: 123},
+		{s: "1.5", d: new(userDefined), wantusrdef: 1.5},
+		{s: []byte{1, 2, 3}, d: new(userDefinedSlice), wanterr: `unsupported Scan, storing driver.Value type []uint8 into type *sql.userDefinedSlice`},
+		{s: "str", d: new(userDefinedString), wantusrstr: "str"},
+
+		// Other errors
+		{s: complex(1, 2), d: &scanstr, wanterr: `unsupported Scan, storing driver.Value type complex128 into type *string`},
+	}
 }
 
 func intPtrValue(intptr interface{}) interface{} {
@@ -210,7 +213,7 @@ func timeValue(ptr interface{}) time.Time {
 }
 
 func TestConversions(t *testing.T) {
-	for n, ct := range conversionTests {
+	for n, ct := range conversionTests() {
 		err := convertAssign(ct.d, ct.s)
 		errstr := ""
 		if err != nil {
diff --git a/libgo/go/go/types/assignments.go b/libgo/go/go/types/assignments.go
index e5ea071..98c9e12 100644
--- a/libgo/go/go/types/assignments.go
+++ b/libgo/go/go/types/assignments.go
@@ -154,8 +154,11 @@ func (check *Checker) assignVar(lhs ast.Expr, x *operand) Type {
 	var v_used bool
 	if ident != nil {
 		if _, obj := check.scope.LookupParent(ident.Name, token.NoPos); obj != nil {
-			v, _ = obj.(*Var)
-			if v != nil {
+			// It's ok to mark non-local variables, but ignore variables
+			// from other packages to avoid potential race conditions with
+			// dot-imported variables.
+			if w, _ := obj.(*Var); w != nil && w.pkg == check.pkg {
+				v = w
 				v_used = v.used
 			}
 		}
@@ -249,6 +252,7 @@ func (check *Checker) assignVars(lhs, rhs []ast.Expr) {
 	l := len(lhs)
 	get, r, commaOk := unpack(func(x *operand, i int) { check.multiExpr(x, rhs[i]) }, len(rhs), l == 2)
 	if get == nil {
+		check.useLHS(lhs...)
 		return // error reported by unpack
 	}
 	if l != r {
diff --git a/libgo/go/go/types/call.go b/libgo/go/go/types/call.go
index 345df66..8fe65e4 100644
--- a/libgo/go/go/types/call.go
+++ b/libgo/go/go/types/call.go
@@ -90,15 +90,52 @@ func (check *Checker) call(x *operand, e *ast.CallExpr) exprKind {
 // use type-checks each argument.
 // Useful to make sure expressions are evaluated
 // (and variables are "used") in the presence of other errors.
+// The arguments may be nil.
 func (check *Checker) use(arg ...ast.Expr) {
 	var x operand
 	for _, e := range arg {
-		if e != nil { // be safe
+		// The nil check below is necessary since certain AST fields
+		// may legally be nil (e.g., the ast.SliceExpr.High field).
+		if e != nil {
 			check.rawExpr(&x, e, nil)
 		}
 	}
 }
 
+// useLHS is like use, but doesn't "use" top-level identifiers.
+// It should be called instead of use if the arguments are
+// expressions on the lhs of an assignment.
+// The arguments must not be nil.
+func (check *Checker) useLHS(arg ...ast.Expr) {
+	var x operand
+	for _, e := range arg {
+		// If the lhs is an identifier denoting a variable v, this assignment
+		// is not a 'use' of v. Remember current value of v.used and restore
+		// after evaluating the lhs via check.rawExpr.
+		var v *Var
+		var v_used bool
+		if ident, _ := unparen(e).(*ast.Ident); ident != nil {
+			// never type-check the blank name on the lhs
+			if ident.Name == "_" {
+				continue
+			}
+			if _, obj := check.scope.LookupParent(ident.Name, token.NoPos); obj != nil {
+				// It's ok to mark non-local variables, but ignore variables
+				// from other packages to avoid potential race conditions with
+				// dot-imported variables.
+				if w, _ := obj.(*Var); w != nil && w.pkg == check.pkg {
+					v = w
+					v_used = v.used
+				}
+			}
+		}
+		check.rawExpr(&x, e, nil)
+		if v != nil {
+			v.used = v_used // restore v.used
+		}
+	}
+}
+
 // useGetter is like use, but takes a getter instead of a list of expressions.
 // It should be called instead of use if a getter is present to avoid repeated
 // evaluation of the first argument (since the getter was likely obtained via
diff --git a/libgo/go/go/types/decl.go b/libgo/go/go/types/decl.go
index 7428f8f..9b250b3 100644
--- a/libgo/go/go/types/decl.go
+++ b/libgo/go/go/types/decl.go
@@ -111,7 +111,11 @@ func (check *Checker) constDecl(obj *Const, typ, init ast.Expr) {
 	if typ != nil {
 		t := check.typ(typ)
 		if !isConstType(t) {
-			check.errorf(typ.Pos(), "invalid constant type %s", t)
+			// don't report an error if the type is an invalid C (defined) type
+			// (issue #22090)
+			if t.Underlying() != Typ[Invalid] {
+				check.errorf(typ.Pos(), "invalid constant type %s", t)
+			}
 			obj.typ = Typ[Invalid]
 			return
 		}
diff --git a/libgo/go/go/types/stmt.go b/libgo/go/go/types/stmt.go
index 1292f5c..5221bcc 100644
--- a/libgo/go/go/types/stmt.go
+++ b/libgo/go/go/types/stmt.go
@@ -731,6 +731,9 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		// declaration, but the post statement must not."
 		if s, _ := s.Post.(*ast.AssignStmt); s != nil && s.Tok == token.DEFINE {
 			check.softErrorf(s.Pos(), "cannot declare in post statement")
+			// Don't call useLHS here because we want to use the lhs in
+			// this erroneous statement so that we don't get errors about
+			// these lhs variables being declared but not used.
 			check.use(s.Lhs...) // avoid follow-up errors
 		}
 		check.stmt(inner, s.Body)
diff --git a/libgo/go/go/types/testdata/importC.src b/libgo/go/go/types/testdata/importC.src
index 31436be..f50f7f3 100644
--- a/libgo/go/go/types/testdata/importC.src
+++ b/libgo/go/go/types/testdata/importC.src
@@ -8,3 +8,28 @@ import "C"
 import _ /* ERROR cannot rename import "C" */ "C"
 import foo /* ERROR cannot rename import "C" */ "C"
 import . /* ERROR cannot rename import "C" */ "C"
+
+// Test cases extracted from issue #22090.
+
+import "unsafe"
+
+const _ C.int = 0xff // no error due to invalid constant type
+
+type T struct {
+	Name    string
+	Ordinal int
+}
+
+func f(args []T) {
+	var s string
+	for i, v := range args {
+		cname := C.CString(v.Name)
+		args[i].Ordinal = int(C.sqlite3_bind_parameter_index(s, cname)) // no error due to i not being "used"
+		C.free(unsafe.Pointer(cname))
+	}
+}
+
+type CType C.Type
+
+const _ CType = C.X // no error due to invalid constant type
+const _ = C.X
diff --git a/libgo/go/go/types/typexpr.go b/libgo/go/go/types/typexpr.go
index 0ab6dfd..92ab06b 100644
--- a/libgo/go/go/types/typexpr.go
+++ b/libgo/go/go/types/typexpr.go
@@ -86,6 +86,9 @@ func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, path []*TypeNa
 		}
 
 	case *Var:
+		// It's ok to mark non-local variables, but ignore variables
+		// from other packages to avoid potential race conditions with
+		// dot-imported variables.
 		if obj.pkg == check.pkg {
 			obj.used = true
 		}
diff --git a/libgo/go/net/rpc/server.go b/libgo/go/net/rpc/server.go
index a021292..96e6973 100644
--- a/libgo/go/net/rpc/server.go
+++ b/libgo/go/net/rpc/server.go
@@ -296,7 +296,7 @@ func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
 		// Method needs three ins: receiver, *args, *reply.
 		if mtype.NumIn() != 3 {
 			if reportErr {
-				log.Println("method", mname, "has wrong number of ins:", mtype.NumIn())
+				log.Printf("rpc.Register: method %q has %d input parameters; needs exactly three\n", mname, mtype.NumIn())
 			}
 			continue
 		}
@@ -304,7 +304,7 @@ func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
 		argType := mtype.In(1)
 		if !isExportedOrBuiltinType(argType) {
 			if reportErr {
-				log.Println(mname, "argument type not exported:", argType)
+				log.Printf("rpc.Register: argument type of method %q is not exported: %q\n", mname, argType)
 			}
 			continue
 		}
@@ -312,28 +312,28 @@ func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
 		replyType := mtype.In(2)
 		if replyType.Kind() != reflect.Ptr {
 			if reportErr {
-				log.Println("method", mname, "reply type not a pointer:", replyType)
+				log.Printf("rpc.Register: reply type of method %q is not a pointer: %q\n", mname, replyType)
 			}
 			continue
 		}
 		// Reply type must be exported.
 		if !isExportedOrBuiltinType(replyType) {
 			if reportErr {
-				log.Println("method", mname, "reply type not exported:", replyType)
+				log.Printf("rpc.Register: reply type of method %q is not exported: %q\n", mname, replyType)
 			}
 			continue
 		}
 		// Method needs one out.
 		if mtype.NumOut() != 1 {
 			if reportErr {
-				log.Println("method", mname, "has wrong number of outs:", mtype.NumOut())
+				log.Printf("rpc.Register: method %q has %d output parameters; needs exactly one\n", mname, mtype.NumOut())
 			}
 			continue
 		}
 		// The return type of the method must be error.
 		if returnType := mtype.Out(0); returnType != typeOfError {
 			if reportErr {
-				log.Println("method", mname, "returns", returnType.String(), "not error")
+				log.Printf("rpc.Register: return type of method %q is %q, must be error\n", mname, returnType)
 			}
 			continue
 		}
diff --git a/libgo/go/os/error_plan9.go b/libgo/go/os/error_plan9.go
index a673439..b82bf0d 100644
--- a/libgo/go/os/error_plan9.go
+++ b/libgo/go/os/error_plan9.go
@@ -5,7 +5,7 @@
 package os
 
 func isExist(err error) bool {
-	return checkErrMessageContent(err, " exists")
+	return checkErrMessageContent(err, "exists", "is a directory")
 }
 
 func isNotExist(err error) bool {
diff --git a/libgo/go/os/getwd.go b/libgo/go/os/getwd.go
index 87ad8eb..6d25466 100644
--- a/libgo/go/os/getwd.go
+++ b/libgo/go/os/getwd.go
@@ -24,7 +24,7 @@ var useSyscallwd = func(error) bool { return true }
 // reached via multiple paths (due to symbolic links),
 // Getwd may return any one of them.
 func Getwd() (dir string, err error) {
-	if runtime.GOOS == "windows" {
+	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
 		return syscall.Getwd()
 	}
 
diff --git a/libgo/go/runtime/crash_test.go b/libgo/go/runtime/crash_test.go
index 06200c7..7a099be 100644
--- a/libgo/go/runtime/crash_test.go
+++ b/libgo/go/runtime/crash_test.go
@@ -632,3 +632,20 @@ retry:
 	}
 	t.Errorf("test ran %d times without producing expected output", tries)
 }
+
+func TestBadTraceback(t *testing.T) {
+	if runtime.Compiler == "gccgo" {
+		t.Skip("gccgo does not do a hex dump")
+	}
+	output := runTestProg(t, "testprog", "BadTraceback")
+	for _, want := range []string{
+		"runtime: unexpected return pc",
+		"called from 0xbad",
+		"00000bad",    // Smashed LR in hex dump
+		"<main.badLR", // Symbolization in hex dump (badLR1 or badLR2)
+	} {
+		if !strings.Contains(output, want) {
+			t.Errorf("output does not contain %q:\n%s", want, output)
+		}
+	}
+}
diff --git a/libgo/go/runtime/error.go b/libgo/go/runtime/error.go
index 44e63d8..34b7d37 100644
--- a/libgo/go/runtime/error.go
+++ b/libgo/go/runtime/error.go
@@ -138,8 +138,7 @@ func typestring(x interface{}) string {
 	return *e._type.string
 }
 
-// For calling from C.
-// Prints an argument passed to panic.
+// printany prints an argument passed to panic.
 func printany(i interface{}) {
 	switch v := i.(type) {
 	case nil:
diff --git a/libgo/go/runtime/panic.go b/libgo/go/runtime/panic.go
index 24d78eca..fbdb17e 100644
--- a/libgo/go/runtime/panic.go
+++ b/libgo/go/runtime/panic.go
@@ -403,12 +403,15 @@ func preprintpanics(p *_panic) {
 }
 
 // Print all currently active panics. Used when crashing.
+// Should only be called after preprintpanics.
 func printpanics(p *_panic) {
 	if p.link != nil {
 		printpanics(p.link)
 		print("\t")
 	}
 	print("panic: ")
+	// Because of preprintpanics, p.arg cannot be an error or
+	// stringer, so this won't call into user code.
 	printany(p.arg)
 	if p.recovered {
 		print(" [recovered]")
@@ -833,7 +836,7 @@ var panicking uint32
 // so that two concurrent panics don't overlap their output.
 var paniclk mutex
 
-// startpanic_m implements unrecoverable panic.
+// startpanic_m prepares for an unrecoverable panic.
 //
 // It can have write barriers because the write barrier explicitly
 // ignores writes once dying > 0.
@@ -841,14 +844,14 @@ var paniclk mutex
 //go:yeswritebarrierrec
 func startpanic() {
 	_g_ := getg()
-	// Uncomment when mheap_ is in Go.
-	// if mheap_.cachealloc.size == 0 { // very early
-	//	print("runtime: panic before malloc heap initialized\n")
-	//	_g_.m.mallocing = 1 // tell rest of panic not to try to malloc
-	// } else
-	if _g_.m.mcache == nil { // can happen if called from signal handler or throw
-		_g_.m.mcache = allocmcache()
+	if mheap_.cachealloc.size == 0 { // very early
+		print("runtime: panic before malloc heap initialized\n")
 	}
+	// Disallow malloc during an unrecoverable panic. A panic
+	// could happen in a signal handler, or in a throw, or inside
+	// malloc itself. We want to catch if an allocation ever does
+	// happen (even if we're not in one of these situations).
+	_g_.m.mallocing++
 
 	switch _g_.m.dying {
 	case 0:
@@ -934,6 +937,9 @@ func dopanic(unused int) {
 	exit(2)
 }
 
+// canpanic returns false if a signal should throw instead of
+// panicking.
+//
 //go:nosplit
 func canpanic(gp *g) bool {
 	// Note that g is m->gsignal, different from gp.
diff --git a/libgo/go/runtime/pprof/pprof.go b/libgo/go/runtime/pprof/pprof.go
index 8a562e2..be4e869 100644
--- a/libgo/go/runtime/pprof/pprof.go
+++ b/libgo/go/runtime/pprof/pprof.go
@@ -350,7 +350,8 @@ type countProfile interface {
 // as the pprof-proto format output. Translations from cycle count to time duration
 // are done because The proto expects count and time (nanoseconds) instead of count
 // and the number of cycles for block, contention profiles.
-func printCountCycleProfile(w io.Writer, countName, cycleName string, records []runtime.BlockProfileRecord) error {
+// Possible 'scaler' functions are scaleBlockProfile and scaleMutexProfile.
+func printCountCycleProfile(w io.Writer, countName, cycleName string, scaler func(int64, float64) (int64, float64), records []runtime.BlockProfileRecord) error {
 	// Output profile in protobuf form.
 	b := newProfileBuilder(w)
 	b.pbValueType(tagProfile_PeriodType, countName, "count")
@@ -363,8 +364,9 @@ func printCountCycleProfile(w io.Writer, countName, cycleName string, records []
 	values := []int64{0, 0}
 	var locs []uint64
 	for _, r := range records {
-		values[0] = int64(r.Count)
-		values[1] = int64(float64(r.Cycles) / cpuGHz) // to nanoseconds
+		count, nanosec := scaler(r.Count, float64(r.Cycles)/cpuGHz)
+		values[0] = count
+		values[1] = int64(nanosec)
 		locs = locs[:0]
 		for _, addr := range r.Stack() {
 			// For count profiles, all stack addresses are
@@ -820,7 +822,7 @@ func writeBlock(w io.Writer, debug int) error {
 	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })
 
 	if debug <= 0 {
-		return printCountCycleProfile(w, "contentions", "delay", p)
+		return printCountCycleProfile(w, "contentions", "delay", scaleBlockProfile, p)
 	}
 
 	b := bufio.NewWriter(w)
@@ -847,6 +849,14 @@ func writeBlock(w io.Writer, debug int) error {
 	return b.Flush()
 }
 
+func scaleBlockProfile(cnt int64, ns float64) (int64, float64) {
+	// Do nothing.
+	// The current way of block profile sampling makes it
+	// hard to compute the unsampled number. The legacy block
+	// profile parse doesn't attempt to scale or unsample.
+	return cnt, ns
+}
+
 // writeMutex writes the current mutex profile to w.
 func writeMutex(w io.Writer, debug int) error {
 	// TODO(pjw): too much common code with writeBlock. FIX!
@@ -864,7 +874,7 @@ func writeMutex(w io.Writer, debug int) error {
 	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })
 
 	if debug <= 0 {
-		return printCountCycleProfile(w, "contentions", "delay", p)
+		return printCountCycleProfile(w, "contentions", "delay", scaleMutexProfile, p)
 	}
 
 	b := bufio.NewWriter(w)
@@ -892,4 +902,9 @@ func writeMutex(w io.Writer, debug int) error {
 	return b.Flush()
 }
 
+func scaleMutexProfile(cnt int64, ns float64) (int64, float64) {
+	period := runtime.SetMutexProfileFraction(-1)
+	return cnt * int64(period), ns * float64(period)
+}
+
 func runtime_cyclesPerSecond() int64
diff --git a/libgo/go/runtime/rwmutex.go b/libgo/go/runtime/rwmutex.go
index 7eeb559..a6da4c9 100644
--- a/libgo/go/runtime/rwmutex.go
+++ b/libgo/go/runtime/rwmutex.go
@@ -10,7 +10,7 @@ import (
 
 // This is a copy of sync/rwmutex.go rewritten to work in the runtime.
 
-// An rwmutex is a reader/writer mutual exclusion lock.
+// A rwmutex is a reader/writer mutual exclusion lock.
 // The lock can be held by an arbitrary number of readers or a single writer.
 // This is a variant of sync.RWMutex, for the runtime package.
 // Like mutex, rwmutex blocks the calling M.
diff --git a/libgo/go/runtime/signal_sighandler.go b/libgo/go/runtime/signal_sighandler.go
index c042162..698629d 100644
--- a/libgo/go/runtime/signal_sighandler.go
+++ b/libgo/go/runtime/signal_sighandler.go
@@ -40,6 +40,11 @@ func sighandler(sig uint32, info *_siginfo_t, ctxt unsafe.Pointer, gp *g) {
 	if sig < uint32(len(sigtable)) {
 		flags = sigtable[sig].flags
 	}
+	if flags&_SigPanic != 0 && gp.throwsplit {
+		// We can't safely sigpanic because it may grow the
+		// stack. Abort in the signal handler instead.
+		flags = (flags &^ _SigPanic) | _SigThrow
+	}
 	if c.sigcode() != _SI_USER && flags&_SigPanic != 0 {
 		// Emulate gc by passing arguments out of band,
 		// although we don't really have to.
diff --git a/libgo/go/runtime/signal_unix.go b/libgo/go/runtime/signal_unix.go
index 8517148..02d5348 100644
--- a/libgo/go/runtime/signal_unix.go
+++ b/libgo/go/runtime/signal_unix.go
@@ -320,6 +320,12 @@ func sigtrampgo(sig uint32, info *_siginfo_t, ctx unsafe.Pointer) {
 // the signal handler. The effect is that the program will act as
 // though the function that got the signal simply called sigpanic
 // instead.
+//
+// This must NOT be nosplit because the linker doesn't know where
+// sigpanic calls can be injected.
+//
+// The signal handler must not inject a call to sigpanic if
+// getg().throwsplit, since sigpanic may need to grow the stack.
 func sigpanic() {
 	g := getg()
 	if !canpanic(g) {
diff --git a/libgo/go/runtime/time.go b/libgo/go/runtime/time.go
index 93181fd..b707590 100644
--- a/libgo/go/runtime/time.go
+++ b/libgo/go/runtime/time.go
@@ -59,6 +59,7 @@ func (t *timer) assignBucket() *timersBucket {
 	return t.tb
 }
 
+//go:notinheap
 type timersBucket struct {
 	lock         mutex
 	gp           *g
diff --git a/libgo/go/sync/rwmutex.go b/libgo/go/sync/rwmutex.go
index cb2dfe1..4e9e819 100644
--- a/libgo/go/sync/rwmutex.go
+++ b/libgo/go/sync/rwmutex.go
@@ -13,11 +13,11 @@ import (
 // There is a modified copy of this file in runtime/rwmutex.go.
 // If you make any changes here, see if you should make them there.
 
-// An RWMutex is a reader/writer mutual exclusion lock.
+// A RWMutex is a reader/writer mutual exclusion lock.
 // The lock can be held by an arbitrary number of readers or a single writer.
 // The zero value for a RWMutex is an unlocked mutex.
 //
-// An RWMutex must not be copied after first use.
+// A RWMutex must not be copied after first use.
 //
 // If a goroutine holds a RWMutex for reading and another goroutine might
 // call Lock, no goroutine should expect to be able to acquire a read lock
@@ -108,7 +108,7 @@ func (rw *RWMutex) Lock() {
 // not locked for writing on entry to Unlock.
 //
 // As with Mutexes, a locked RWMutex is not associated with a particular
-// goroutine. One goroutine may RLock (Lock) an RWMutex and then
+// goroutine. One goroutine may RLock (Lock) a RWMutex and then
 // arrange for another goroutine to RUnlock (Unlock) it.
 func (rw *RWMutex) Unlock() {
 	if race.Enabled {
diff --git a/libgo/misc/cgo/errors/ptr_test.go b/libgo/misc/cgo/errors/ptr_test.go
index d295a58..fe8dfff 100644
--- a/libgo/misc/cgo/errors/ptr_test.go
+++ b/libgo/misc/cgo/errors/ptr_test.go
@@ -349,6 +349,14 @@ var ptrTests = []ptrTest{
 		body:    `var wg sync.WaitGroup; wg.Add(100); for i := 0; i < 100; i++ { go func(i int) { for j := 0; j < 100; j++ { C.f(); runtime.GOMAXPROCS(i) }; wg.Done() }(i) }; wg.Wait()`,
 		fail:    false,
 	},
+	{
+		// Test poller deadline with cgocheck=2.  Issue #23435.
+		name:    "deadline",
+		c:       `#define US 10`,
+		imports: []string{"os", "time"},
+		body:    `r, _, _ := os.Pipe(); r.SetDeadline(time.Now().Add(C.US * time.Microsecond))`,
+		fail:    false,
+	},
 }
 
 func TestPointerChecks(t *testing.T) {
diff --git a/libgo/misc/cgo/testcarchive/carchive_test.go b/libgo/misc/cgo/testcarchive/carchive_test.go
index e3f6795..4a8cc0f 100644
--- a/libgo/misc/cgo/testcarchive/carchive_test.go
+++ b/libgo/misc/cgo/testcarchive/carchive_test.go
@@ -695,3 +695,50 @@ func TestCompileWithoutShared(t *testing.T) {
 	t.Logf("%s", out)
 	expectSignal(t, err, syscall.SIGPIPE)
 }
+
+// Test that installing a second time recreates the header files.
+func TestCachedInstall(t *testing.T) {
+	defer os.RemoveAll("pkg")
+
+	h1 := filepath.Join("pkg", libgodir, "libgo.h")
+	h2 := filepath.Join("pkg", libgodir, "p.h")
+
+	buildcmd := []string{"go", "install", "-i", "-buildmode=c-archive", "libgo"}
+
+	cmd := exec.Command(buildcmd[0], buildcmd[1:]...)
+	cmd.Env = gopathEnv
+	t.Log(buildcmd)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Logf("%s", out)
+		t.Fatal(err)
+	}
+
+	if _, err := os.Stat(h1); 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 {
+		t.Fatal(err)
+	}
+
+	cmd = exec.Command(buildcmd[0], buildcmd[1:]...)
+	cmd.Env = gopathEnv
+	t.Log(buildcmd)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Logf("%s", out)
+		t.Fatal(err)
+	}
+
+	if _, err := os.Stat(h1); 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)
+	}
+}
diff --git a/libgo/misc/cgo/testcshared/cshared_test.go b/libgo/misc/cgo/testcshared/cshared_test.go
index 49be092..e43422d 100644
--- a/libgo/misc/cgo/testcshared/cshared_test.go
+++ b/libgo/misc/cgo/testcshared/cshared_test.go
@@ -7,6 +7,7 @@ package cshared_test
 import (
 	"debug/elf"
 	"fmt"
+	"io/ioutil"
 	"log"
 	"os"
 	"os/exec"
@@ -55,7 +56,8 @@ func TestMain(m *testing.M) {
 
 	androiddir = fmt.Sprintf("/data/local/tmp/testcshared-%d", os.Getpid())
 	if GOOS == "android" {
-		cmd := exec.Command("adb", "shell", "mkdir", "-p", androiddir)
+		args := append(adbCmd(), "shell", "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)
@@ -154,11 +156,19 @@ 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 GOOS != "android" {
 		return
 	}
-	args := []string{"adb", "push", filename, fmt.Sprintf("%s/%s", androiddir, filename)}
+	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)
@@ -169,7 +179,7 @@ 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 := []string{"adb", "shell"}
+	args := append(adbCmd(), "shell")
 	// Propagate LD_LIBRARY_PATH to the adb shell invocation.
 	for _, e := range env {
 		if strings.Index(e, "LD_LIBRARY_PATH=") != -1 {
@@ -237,7 +247,7 @@ func createHeaders() error {
 	}
 
 	if GOOS == "android" {
-		args = []string{"adb", "push", libgoname, fmt.Sprintf("%s/%s", androiddir, libgoname)}
+		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 {
@@ -270,7 +280,8 @@ func cleanupAndroid() {
 	if GOOS != "android" {
 		return
 	}
-	cmd := exec.Command("adb", "shell", "rm", "-rf", androiddir)
+	args := append(adbCmd(), "shell", "rm", "-rf", androiddir)
+	cmd := exec.Command(args[0], args[1:]...)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		log.Fatalf("cleanupAndroid failed: %v\n%s\n", err, out)
@@ -477,3 +488,99 @@ func TestPIE(t *testing.T) {
 		}
 	}
 }
+
+// Test that installing a second time recreates the header files.
+func TestCachedInstall(t *testing.T) {
+	tmpdir, err := ioutil.TempDir("", "cshared")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// defer os.RemoveAll(tmpdir)
+
+	copyFile(t, filepath.Join(tmpdir, "src", "libgo", "libgo.go"), filepath.Join("src", "libgo", "libgo.go"))
+	copyFile(t, filepath.Join(tmpdir, "src", "p", "p.go"), filepath.Join("src", "p", "p.go"))
+
+	env := append(os.Environ(), "GOPATH="+tmpdir)
+
+	buildcmd := []string{"go", "install", "-x", "-i", "-buildmode=c-shared", "-installsuffix", "testcshared", "libgo"}
+
+	cmd := exec.Command(buildcmd[0], buildcmd[1:]...)
+	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 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.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)
+	}
+	if _, err := os.Stat(ph); err != nil {
+		t.Errorf("p.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 := ioutil.ReadFile(src)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(filepath.Dir(dst), 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := ioutil.WriteFile(dst, data, 0666); err != nil {
+		t.Fatal(err)
+	}
+}
diff --git a/libgo/misc/cgo/testshared/shared_test.go b/libgo/misc/cgo/testshared/shared_test.go
index f1e8f06..cf049ec 100644
--- a/libgo/misc/cgo/testshared/shared_test.go
+++ b/libgo/misc/cgo/testshared/shared_test.go
@@ -351,10 +351,10 @@ func readNotes(f *elf.File) ([]*note, error) {
 
 func dynStrings(t *testing.T, path string, flag elf.DynTag) []string {
 	f, err := elf.Open(path)
-	defer f.Close()
 	if err != nil {
 		t.Fatalf("elf.Open(%q) failed: %v", path, err)
 	}
+	defer f.Close()
 	dynstrings, err := f.DynString(flag)
 	if err != nil {
 		t.Fatalf("DynString(%s) failed on %s: %v", flag, path, err)
@@ -598,7 +598,6 @@ func TestThreeGopathShlibs(t *testing.T) {
 // If gccgo is not available or not new enough call t.Skip. Otherwise,
 // return a build.Context that is set up for gccgo.
 func prepGccgo(t *testing.T) build.Context {
-	t.Skip("golang.org/issue/22472")
 	gccgoName := os.Getenv("GCCGO")
 	if gccgoName == "" {
 		gccgoName = "gccgo"
@@ -648,8 +647,6 @@ func TestGoPathShlibGccgo(t *testing.T) {
 // library with gccgo, another GOPATH package that depends on the first and an
 // executable that links the second library.
 func TestTwoGopathShlibsGccgo(t *testing.T) {
-	t.Skip("golang.org/issue/22224")
-
 	gccgoContext := prepGccgo(t)
 
 	libgoRE := regexp.MustCompile("libgo.so.[0-9]+")