[dev.fuzz] all: merge master into dev.fuzz

Change-Id: I5d8c8329ccc9d747bd81ade6b1cb7cb8ae2e94b2

6 files changed, 180 insertions, 255 deletions

diff --git a/src/cmd/cgo/ast.go b/src/cmd/cgo/ast.go
index 54d6bc2559..a073407a96 100644
--- a/src/cmd/cgo/ast.go
+++ b/src/cmd/cgo/ast.go
@@ -13,7 +13,6 @@ import (
 	"go/scanner"
 	"go/token"
 	"os"
-	"path/filepath"
 	"strings"
 )
 
@@ -44,14 +43,7 @@ func sourceLine(n ast.Node) int {
 // attached to the import "C" comment, a list of references to C.xxx,
 // a list of exported functions, and the actual AST, to be rewritten and
 // printed.
-func (f *File) ParseGo(name string, src []byte) {
-	// Create absolute path for file, so that it will be used in error
-	// messages and recorded in debug line number information.
-	// This matches the rest of the toolchain. See golang.org/issue/5122.
-	if aname, err := filepath.Abs(name); err == nil {
-		name = aname
-	}
-
+func (f *File) ParseGo(abspath string, src []byte) {
 	// Two different parses: once with comments, once without.
 	// The printer is not good enough at printing comments in the
 	// right place when we start editing the AST behind its back,
@@ -60,8 +52,8 @@ func (f *File) ParseGo(name string, src []byte) {
 	// and reprinting.
 	// In cgo mode, we ignore ast2 and just apply edits directly
 	// the text behind ast1. In godefs mode we modify and print ast2.
-	ast1 := parse(name, src, parser.ParseComments)
-	ast2 := parse(name, src, 0)
+	ast1 := parse(abspath, src, parser.ParseComments)
+	ast2 := parse(abspath, src, 0)
 
 	f.Package = ast1.Name.Name
 	f.Name = make(map[string]*Name)
@@ -88,7 +80,7 @@ func (f *File) ParseGo(name string, src []byte) {
 				cg = d.Doc
 			}
 			if cg != nil {
-				f.Preamble += fmt.Sprintf("#line %d %q\n", sourceLine(cg), name)
+				f.Preamble += fmt.Sprintf("#line %d %q\n", sourceLine(cg), abspath)
 				f.Preamble += commentText(cg) + "\n"
 				f.Preamble += "#line 1 \"cgo-generated-wrapper\"\n"
 			}
diff --git a/src/cmd/cgo/doc.go b/src/cmd/cgo/doc.go
index b3f371b08c..e782c866ac 100644
--- a/src/cmd/cgo/doc.go
+++ b/src/cmd/cgo/doc.go
@@ -721,7 +721,7 @@ linkage to the desired libraries. The main function is provided by
 _cgo_main.c:
 
 	int main() { return 0; }
-	void crosscall2(void(*fn)(void*, int, uintptr_t), void *a, int c, uintptr_t ctxt) { }
+	void crosscall2(void(*fn)(void*), void *a, int c, uintptr_t ctxt) { }
 	uintptr_t _cgo_wait_runtime_init_done(void) { return 0; }
 	void _cgo_release_context(uintptr_t ctxt) { }
 	char* _cgo_topofstack(void) { return (char*)0; }
diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 9179b5490e..111a309eb5 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -298,7 +298,7 @@ func (p *Package) guessKinds(f *File) []*Name {
 			continue
 		}
 
-		if goos == "darwin" && strings.HasSuffix(n.C, "Ref") {
+		if (goos == "darwin" || goos == "ios") && 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}
@@ -2448,6 +2448,18 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 			tt := *t
 			tt.C = &TypeRepr{"%s %s", []interface{}{dt.Kind, tag}}
 			tt.Go = c.Ident("struct{}")
+			if dt.Kind == "struct" {
+				// We don't know what the representation of this struct is, so don't let
+				// anyone allocate one on the Go side. As a side effect of this annotation,
+				// pointers to this type will not be considered pointers in Go. They won't
+				// get writebarrier-ed or adjusted during a stack copy. This should handle
+				// all the cases badPointerTypedef used to handle, but hopefully will
+				// continue to work going forward without any more need for cgo changes.
+				tt.NotInHeap = true
+				// TODO: we should probably do the same for unions. Unions can't live
+				// on the Go heap, right? It currently doesn't work for unions because
+				// they are defined as a type alias for struct{}, not a defined type.
+			}
 			typedef[name.Name] = &tt
 			break
 		}
@@ -2518,6 +2530,7 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 		}
 		t.Go = name
 		t.BadPointer = sub.BadPointer
+		t.NotInHeap = sub.NotInHeap
 		if unionWithPointer[sub.Go] {
 			unionWithPointer[t.Go] = true
 		}
@@ -2528,6 +2541,7 @@ func (c *typeConv) loadType(dtype dwarf.Type, pos token.Pos, parent string) *Typ
 			tt := *t
 			tt.Go = sub.Go
 			tt.BadPointer = sub.BadPointer
+			tt.NotInHeap = sub.NotInHeap
 			typedef[name.Name] = &tt
 		}
 
@@ -2831,21 +2845,11 @@ func (c *typeConv) Struct(dt *dwarf.StructType, pos token.Pos) (expr *ast.Struct
 		tgo := t.Go
 		size := t.Size
 		talign := t.Align
-		if f.BitSize > 0 {
-			switch f.BitSize {
-			case 8, 16, 32, 64:
-			default:
-				continue
-			}
-			size = f.BitSize / 8
-			name := tgo.(*ast.Ident).String()
-			if strings.HasPrefix(name, "int") {
-				name = "int"
-			} else {
-				name = "uint"
-			}
-			tgo = ast.NewIdent(name + fmt.Sprint(f.BitSize))
-			talign = size
+		if f.BitOffset > 0 || f.BitSize > 0 {
+			// The layout of bitfields is implementation defined,
+			// so we don't know how they correspond to Go fields
+			// even if they are aligned at byte boundaries.
+			continue
 		}
 
 		if talign > 0 && f.ByteOffset%talign != 0 {
@@ -3036,6 +3040,7 @@ func (c *typeConv) anonymousStructTypedef(dt *dwarf.TypedefType) bool {
 // 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.
+// Note: DEPRECATED. There is now a better solution. Search for NotInHeap in this file.
 func (c *typeConv) badPointerTypedef(dt *dwarf.TypedefType) bool {
 	if c.badCFType(dt) {
 		return true
@@ -3070,7 +3075,7 @@ func (c *typeConv) badCFType(dt *dwarf.TypedefType) bool {
 	// 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.
-	if goos != "darwin" {
+	if goos != "darwin" && goos != "ios" {
 		return false
 	}
 	s := dt.Name
diff --git a/src/cmd/cgo/godefs.go b/src/cmd/cgo/godefs.go
index b4fd9c5a6e..c0d59aee01 100644
--- a/src/cmd/cgo/godefs.go
+++ b/src/cmd/cgo/godefs.go
@@ -16,7 +16,7 @@ import (
 )
 
 // godefs returns the output for -godefs mode.
-func (p *Package) godefs(f *File, srcfile string) string {
+func (p *Package) godefs(f *File) string {
 	var buf bytes.Buffer
 
 	fmt.Fprintf(&buf, "// Code generated by cmd/cgo -godefs; DO NOT EDIT.\n")
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 5a7bb3f87b..c1116e28ec 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -151,7 +151,8 @@ type Type struct {
 	Go         ast.Expr
 	EnumValues map[string]int64
 	Typedef    string
-	BadPointer bool
+	BadPointer bool // this pointer type should be represented as a uintptr (deprecated)
+	NotInHeap  bool // this type should have a go:notinheap annotation
 }
 
 // A FuncType collects information about a function type in both the C and Go worlds.
@@ -169,35 +170,51 @@ func usage() {
 
 var ptrSizeMap = map[string]int64{
 	"386":      4,
+	"alpha":    8,
 	"amd64":    8,
 	"arm":      4,
 	"arm64":    8,
+	"m68k":     4,
 	"mips":     4,
 	"mipsle":   4,
 	"mips64":   8,
 	"mips64le": 8,
+	"nios2":    4,
+	"ppc":      4,
 	"ppc64":    8,
 	"ppc64le":  8,
+	"riscv":    4,
 	"riscv64":  8,
 	"s390":     4,
 	"s390x":    8,
+	"sh":       4,
+	"shbe":     4,
+	"sparc":    4,
 	"sparc64":  8,
 }
 
 var intSizeMap = map[string]int64{
 	"386":      4,
+	"alpha":    8,
 	"amd64":    8,
 	"arm":      4,
 	"arm64":    8,
+	"m68k":     4,
 	"mips":     4,
 	"mipsle":   4,
 	"mips64":   8,
 	"mips64le": 8,
+	"nios2":    4,
+	"ppc":      4,
 	"ppc64":    8,
 	"ppc64le":  8,
+	"riscv":    4,
 	"riscv64":  8,
 	"s390":     4,
 	"s390x":    8,
+	"sh":       4,
+	"shbe":     4,
+	"sparc":    4,
 	"sparc64":  8,
 }
 
@@ -223,10 +240,11 @@ var exportHeader = flag.String("exportheader", "", "where to write export header
 var gccgo = flag.Bool("gccgo", false, "generate files for use with gccgo")
 var gccgoprefix = flag.String("gccgoprefix", "", "-fgo-prefix option used with gccgo")
 var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used with gccgo")
-var gccgoMangleCheckDone bool
-var gccgoNewmanglingInEffect bool
+var gccgoMangler func(string) string
 var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
 var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
+var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")
+
 var goarch, goos string
 
 func main() {
@@ -306,6 +324,13 @@ func main() {
 			input = filepath.Join(*srcDir, input)
 		}
 
+		// Create absolute path for file, so that it will be used in error
+		// messages and recorded in debug line number information.
+		// This matches the rest of the toolchain. See golang.org/issue/5122.
+		if aname, err := filepath.Abs(input); err == nil {
+			input = aname
+		}
+
 		b, err := ioutil.ReadFile(input)
 		if err != nil {
 			fatalf("%s", err)
@@ -314,6 +339,10 @@ func main() {
 			fatalf("%s", err)
 		}
 
+		// Apply trimpath to the file path. The path won't be read from after this point.
+		input, _ = objabi.ApplyRewrites(input, *trimpath)
+		goFiles[i] = input
+
 		f := new(File)
 		f.Edit = edit.NewBuffer(b)
 		f.ParseGo(input, b)
@@ -351,7 +380,7 @@ func main() {
 		p.PackagePath = f.Package
 		p.Record(f)
 		if *godefs {
-			os.Stdout.WriteString(p.godefs(f, input))
+			os.Stdout.WriteString(p.godefs(f))
 		} else {
 			p.writeOutput(f, input)
 		}
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 50d2811f1b..11c53facf8 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -6,6 +6,7 @@ package main
 
 import (
 	"bytes"
+	"cmd/internal/pkgpath"
 	"debug/elf"
 	"debug/macho"
 	"debug/pe"
@@ -15,7 +16,6 @@ import (
 	"go/token"
 	"internal/xcoff"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -59,14 +59,14 @@ func (p *Package) writeDefs() {
 	// Write C main file for using gcc to resolve imports.
 	fmt.Fprintf(fm, "int main() { return 0; }\n")
 	if *importRuntimeCgo {
-		fmt.Fprintf(fm, "void crosscall2(void(*fn)(void*, int, __SIZE_TYPE__), void *a, int c, __SIZE_TYPE__ ctxt) { }\n")
+		fmt.Fprintf(fm, "void crosscall2(void(*fn)(void*), void *a, int c, __SIZE_TYPE__ ctxt) { }\n")
 		fmt.Fprintf(fm, "__SIZE_TYPE__ _cgo_wait_runtime_init_done(void) { return 0; }\n")
 		fmt.Fprintf(fm, "void _cgo_release_context(__SIZE_TYPE__ ctxt) { }\n")
 		fmt.Fprintf(fm, "char* _cgo_topofstack(void) { return (char*)0; }\n")
 	} else {
 		// If we're not importing runtime/cgo, we *are* runtime/cgo,
 		// which provides these functions. We just need a prototype.
-		fmt.Fprintf(fm, "void crosscall2(void(*fn)(void*, int, __SIZE_TYPE__), void *a, int c, __SIZE_TYPE__ ctxt);\n")
+		fmt.Fprintf(fm, "void crosscall2(void(*fn)(void*), void *a, int c, __SIZE_TYPE__ ctxt);\n")
 		fmt.Fprintf(fm, "__SIZE_TYPE__ _cgo_wait_runtime_init_done(void);\n")
 		fmt.Fprintf(fm, "void _cgo_release_context(__SIZE_TYPE__);\n")
 	}
@@ -108,6 +108,9 @@ func (p *Package) writeDefs() {
 	sort.Strings(typedefNames)
 	for _, name := range typedefNames {
 		def := typedef[name]
+		if def.NotInHeap {
+			fmt.Fprintf(fgo2, "//go:notinheap\n")
+		}
 		fmt.Fprintf(fgo2, "type %s ", name)
 		// We don't have source info for these types, so write them out without source info.
 		// Otherwise types would look like:
@@ -183,7 +186,7 @@ func (p *Package) writeDefs() {
 			panic(fmt.Errorf("invalid var kind %q", n.Kind))
 		}
 		if *gccgo {
-			fmt.Fprintf(fc, `extern void *%s __asm__("%s.%s");`, n.Mangle, gccgoSymbolPrefix, n.Mangle)
+			fmt.Fprintf(fc, `extern void *%s __asm__("%s.%s");`, n.Mangle, gccgoSymbolPrefix, gccgoToSymbol(n.Mangle))
 			fmt.Fprintf(&gccgoInit, "\t%s = &%s;\n", n.Mangle, n.C)
 			fmt.Fprintf(fc, "\n")
 		}
@@ -334,6 +337,8 @@ func dynimport(obj string) {
 			if s.Version != "" {
 				targ += "#" + s.Version
 			}
+			checkImportSymName(s.Name)
+			checkImportSymName(targ)
 			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", s.Name, targ, s.Library)
 		}
 		lib, _ := f.ImportedLibraries()
@@ -349,6 +354,7 @@ func dynimport(obj string) {
 			if len(s) > 0 && s[0] == '_' {
 				s = s[1:]
 			}
+			checkImportSymName(s)
 			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", s, s, "")
 		}
 		lib, _ := f.ImportedLibraries()
@@ -363,6 +369,8 @@ func dynimport(obj string) {
 		for _, s := range sym {
 			ss := strings.Split(s, ":")
 			name := strings.Split(ss[0], "@")[0]
+			checkImportSymName(name)
+			checkImportSymName(ss[0])
 			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", name, ss[0], strings.ToLower(ss[1]))
 		}
 		return
@@ -380,6 +388,7 @@ func dynimport(obj string) {
 				// Go symbols.
 				continue
 			}
+			checkImportSymName(s.Name)
 			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", s.Name, s.Name, s.Library)
 		}
 		lib, err := f.ImportedLibraries()
@@ -395,6 +404,23 @@ func dynimport(obj string) {
 	fatalf("cannot parse %s as ELF, Mach-O, PE or XCOFF", obj)
 }
 
+// checkImportSymName checks a symbol name we are going to emit as part
+// of a //go:cgo_import_dynamic pragma. These names come from object
+// files, so they may be corrupt. We are going to emit them unquoted,
+// so while they don't need to be valid symbol names (and in some cases,
+// involving symbol versions, they won't be) they must contain only
+// graphic characters and must not contain Go comments.
+func checkImportSymName(s string) {
+	for _, c := range s {
+		if !unicode.IsGraphic(c) || unicode.IsSpace(c) {
+			fatalf("dynamic symbol %q contains unsupported character", s)
+		}
+	}
+	if strings.Index(s, "//") >= 0 || strings.Index(s, "/*") >= 0 {
+		fatalf("dynamic symbol %q contains Go comment")
+	}
+}
+
 // Construct a gcc struct matching the gc argument frame.
 // Assumes that in gcc, char is 1 byte, short 2 bytes, int 4 bytes, long long 8 bytes.
 // These assumptions are checked by the gccProlog.
@@ -849,7 +875,7 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Wpragmas\"\n")
 	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Waddress-of-packed-member\"\n")
 
-	fmt.Fprintf(fgcc, "extern void crosscall2(void (*fn)(void *, int, __SIZE_TYPE__), void *, int, __SIZE_TYPE__);\n")
+	fmt.Fprintf(fgcc, "extern void crosscall2(void (*fn)(void *), void *, int, __SIZE_TYPE__);\n")
 	fmt.Fprintf(fgcc, "extern __SIZE_TYPE__ _cgo_wait_runtime_init_done(void);\n")
 	fmt.Fprintf(fgcc, "extern void _cgo_release_context(__SIZE_TYPE__);\n\n")
 	fmt.Fprintf(fgcc, "extern char* _cgo_topofstack(void);")
@@ -859,59 +885,48 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 	for _, exp := range p.ExpFunc {
 		fn := exp.Func
 
-		// Construct a gcc struct matching the gc argument and
-		// result frame. The gcc struct will be compiled with
-		// __attribute__((packed)) so all padding must be accounted
-		// for explicitly.
+		// Construct a struct that will be used to communicate
+		// arguments from C to Go. The C and Go definitions
+		// just have to agree. The gcc struct will be compiled
+		// with __attribute__((packed)) so all padding must be
+		// accounted for explicitly.
 		ctype := "struct {\n"
+		gotype := new(bytes.Buffer)
+		fmt.Fprintf(gotype, "struct {\n")
 		off := int64(0)
 		npad := 0
-		if fn.Recv != nil {
-			t := p.cgoType(fn.Recv.List[0].Type)
-			ctype += fmt.Sprintf("\t\t%s recv;\n", t.C)
+		argField := func(typ ast.Expr, namePat string, args ...interface{}) {
+			name := fmt.Sprintf(namePat, args...)
+			t := p.cgoType(typ)
+			if off%t.Align != 0 {
+				pad := t.Align - off%t.Align
+				ctype += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
+				off += pad
+				npad++
+			}
+			ctype += fmt.Sprintf("\t\t%s %s;\n", t.C, name)
+			fmt.Fprintf(gotype, "\t\t%s ", name)
+			noSourceConf.Fprint(gotype, fset, typ)
+			fmt.Fprintf(gotype, "\n")
 			off += t.Size
 		}
+		if fn.Recv != nil {
+			argField(fn.Recv.List[0].Type, "recv")
+		}
 		fntype := fn.Type
 		forFieldList(fntype.Params,
 			func(i int, aname string, atype ast.Expr) {
-				t := p.cgoType(atype)
-				if off%t.Align != 0 {
-					pad := t.Align - off%t.Align
-					ctype += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
-					off += pad
-					npad++
-				}
-				ctype += fmt.Sprintf("\t\t%s p%d;\n", t.C, i)
-				off += t.Size
+				argField(atype, "p%d", i)
 			})
-		if off%p.PtrSize != 0 {
-			pad := p.PtrSize - off%p.PtrSize
-			ctype += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
-			off += pad
-			npad++
-		}
 		forFieldList(fntype.Results,
 			func(i int, aname string, atype ast.Expr) {
-				t := p.cgoType(atype)
-				if off%t.Align != 0 {
-					pad := t.Align - off%t.Align
-					ctype += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
-					off += pad
-					npad++
-				}
-				ctype += fmt.Sprintf("\t\t%s r%d;\n", t.C, i)
-				off += t.Size
+				argField(atype, "r%d", i)
 			})
-		if off%p.PtrSize != 0 {
-			pad := p.PtrSize - off%p.PtrSize
-			ctype += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
-			off += pad
-			npad++
-		}
 		if ctype == "struct {\n" {
 			ctype += "\t\tchar unused;\n" // avoid empty struct
 		}
 		ctype += "\t}"
+		fmt.Fprintf(gotype, "\t}")
 
 		// Get the return type of the wrapper function
 		// compiled by gcc.
@@ -936,7 +951,11 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 		}
 
 		// Build the wrapper function compiled by gcc.
-		s := fmt.Sprintf("%s %s(", gccResult, exp.ExpName)
+		gccExport := ""
+		if goos == "windows" {
+			gccExport = "__declspec(dllexport)"
+		}
+		s := fmt.Sprintf("%s %s %s(", gccExport, gccResult, exp.ExpName)
 		if fn.Recv != nil {
 			s += p.cgoType(fn.Recv.List[0].Type).C.String()
 			s += " recv"
@@ -958,12 +977,23 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 		}
 		fmt.Fprintf(fgcch, "extern %s;\n", s)
 
-		fmt.Fprintf(fgcc, "extern void _cgoexp%s_%s(void *, int, __SIZE_TYPE__);\n", cPrefix, exp.ExpName)
+		fmt.Fprintf(fgcc, "extern void _cgoexp%s_%s(void *);\n", cPrefix, exp.ExpName)
 		fmt.Fprintf(fgcc, "\nCGO_NO_SANITIZE_THREAD")
 		fmt.Fprintf(fgcc, "\n%s\n", s)
 		fmt.Fprintf(fgcc, "{\n")
 		fmt.Fprintf(fgcc, "\t__SIZE_TYPE__ _cgo_ctxt = _cgo_wait_runtime_init_done();\n")
-		fmt.Fprintf(fgcc, "\t%s %v _cgo_a;\n", ctype, p.packedAttribute())
+		// The results part of the argument structure must be
+		// initialized to 0 so the write barriers generated by
+		// the assignments to these fields in Go are safe.
+		//
+		// We use a local static variable to get the zeroed
+		// value of the argument type. This avoids including
+		// string.h for memset, and is also robust to C++
+		// types with constructors. Both GCC and LLVM optimize
+		// this into just zeroing _cgo_a.
+		fmt.Fprintf(fgcc, "\ttypedef %s %v _cgo_argtype;\n", ctype, p.packedAttribute())
+		fmt.Fprintf(fgcc, "\tstatic _cgo_argtype _cgo_zero;\n")
+		fmt.Fprintf(fgcc, "\t_cgo_argtype _cgo_a = _cgo_zero;\n")
 		if gccResult != "void" && (len(fntype.Results.List) > 1 || len(fntype.Results.List[0].Names) > 1) {
 			fmt.Fprintf(fgcc, "\t%s r;\n", gccResult)
 		}
@@ -992,82 +1022,28 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 		fmt.Fprintf(fgcc, "}\n")
 
 		// Build the wrapper function compiled by cmd/compile.
-		goname := "_cgoexpwrap" + cPrefix + "_"
-		if fn.Recv != nil {
-			goname += fn.Recv.List[0].Names[0].Name + "_"
-		}
-		goname += exp.Func.Name.Name
+		// This unpacks the argument struct above and calls the Go function.
 		fmt.Fprintf(fgo2, "//go:cgo_export_dynamic %s\n", exp.ExpName)
 		fmt.Fprintf(fgo2, "//go:linkname _cgoexp%s_%s _cgoexp%s_%s\n", cPrefix, exp.ExpName, cPrefix, exp.ExpName)
 		fmt.Fprintf(fgo2, "//go:cgo_export_static _cgoexp%s_%s\n", cPrefix, exp.ExpName)
-		fmt.Fprintf(fgo2, "//go:nosplit\n") // no split stack, so no use of m or g
-		fmt.Fprintf(fgo2, "//go:norace\n")  // must not have race detector calls inserted
-		fmt.Fprintf(fgo2, "func _cgoexp%s_%s(a unsafe.Pointer, n int32, ctxt uintptr) {\n", cPrefix, exp.ExpName)
-		fmt.Fprintf(fgo2, "\tfn := %s\n", goname)
-		// The indirect here is converting from a Go function pointer to a C function pointer.
-		fmt.Fprintf(fgo2, "\t_cgo_runtime_cgocallback(**(**unsafe.Pointer)(unsafe.Pointer(&fn)), a, uintptr(n), ctxt);\n")
-		fmt.Fprintf(fgo2, "}\n")
+		fmt.Fprintf(fgo2, "func _cgoexp%s_%s(a *%s) {\n", cPrefix, exp.ExpName, gotype)
 
 		fmt.Fprintf(fm, "int _cgoexp%s_%s;\n", cPrefix, exp.ExpName)
 
-		// This code uses printer.Fprint, not conf.Fprint,
-		// because we don't want //line comments in the middle
-		// of the function types.
-		fmt.Fprintf(fgo2, "\n")
-		fmt.Fprintf(fgo2, "func %s(", goname)
-		comma := false
-		if fn.Recv != nil {
-			fmt.Fprintf(fgo2, "recv ")
-			printer.Fprint(fgo2, fset, fn.Recv.List[0].Type)
-			comma = true
-		}
-		forFieldList(fntype.Params,
-			func(i int, aname string, atype ast.Expr) {
-				if comma {
-					fmt.Fprintf(fgo2, ", ")
-				}
-				fmt.Fprintf(fgo2, "p%d ", i)
-				printer.Fprint(fgo2, fset, atype)
-				comma = true
-			})
-		fmt.Fprintf(fgo2, ")")
 		if gccResult != "void" {
-			fmt.Fprint(fgo2, " (")
+			// Write results back to frame.
+			fmt.Fprintf(fgo2, "\t")
 			forFieldList(fntype.Results,
 				func(i int, aname string, atype ast.Expr) {
 					if i > 0 {
-						fmt.Fprint(fgo2, ", ")
+						fmt.Fprintf(fgo2, ", ")
 					}
-					fmt.Fprintf(fgo2, "r%d ", i)
-					printer.Fprint(fgo2, fset, atype)
+					fmt.Fprintf(fgo2, "a.r%d", i)
 				})
-			fmt.Fprint(fgo2, ")")
-		}
-		fmt.Fprint(fgo2, " {\n")
-		if gccResult == "void" {
-			fmt.Fprint(fgo2, "\t")
-		} else {
-			// Verify that any results don't contain any
-			// Go pointers.
-			addedDefer := false
-			forFieldList(fntype.Results,
-				func(i int, aname string, atype ast.Expr) {
-					if !p.hasPointer(nil, atype, false) {
-						return
-					}
-					if !addedDefer {
-						fmt.Fprint(fgo2, "\tdefer func() {\n")
-						addedDefer = true
-					}
-					fmt.Fprintf(fgo2, "\t\t_cgoCheckResult(r%d)\n", i)
-				})
-			if addedDefer {
-				fmt.Fprint(fgo2, "\t}()\n")
-			}
-			fmt.Fprint(fgo2, "\treturn ")
+			fmt.Fprintf(fgo2, " = ")
 		}
 		if fn.Recv != nil {
-			fmt.Fprintf(fgo2, "recv.")
+			fmt.Fprintf(fgo2, "a.recv.")
 		}
 		fmt.Fprintf(fgo2, "%s(", exp.Func.Name)
 		forFieldList(fntype.Params,
@@ -1075,9 +1051,20 @@ func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
 				if i > 0 {
 					fmt.Fprint(fgo2, ", ")
 				}
-				fmt.Fprintf(fgo2, "p%d", i)
+				fmt.Fprintf(fgo2, "a.p%d", i)
 			})
 		fmt.Fprint(fgo2, ")\n")
+		if gccResult != "void" {
+			// Verify that any results don't contain any
+			// Go pointers.
+			forFieldList(fntype.Results,
+				func(i int, aname string, atype ast.Expr) {
+					if !p.hasPointer(nil, atype, false) {
+						return
+					}
+					fmt.Fprintf(fgo2, "\t_cgoCheckResult(a.r%d)\n", i)
+				})
+		}
 		fmt.Fprint(fgo2, "}\n")
 	}
 
@@ -1161,7 +1148,7 @@ func (p *Package) writeGccgoExports(fgo2, fm, fgcc, fgcch io.Writer) {
 		// will not be able to link against it from the C
 		// code.
 		goName := "Cgoexp_" + exp.ExpName
-		fmt.Fprintf(fgcc, `extern %s %s %s __asm__("%s.%s");`, cRet, goName, cParams, gccgoSymbolPrefix, goName)
+		fmt.Fprintf(fgcc, `extern %s %s %s __asm__("%s.%s");`, cRet, goName, cParams, gccgoSymbolPrefix, gccgoToSymbol(goName))
 		fmt.Fprint(fgcc, "\n")
 
 		fmt.Fprint(fgcc, "\nCGO_NO_SANITIZE_THREAD\n")
@@ -1195,7 +1182,7 @@ func (p *Package) writeGccgoExports(fgo2, fm, fgcc, fgcch io.Writer) {
 		fmt.Fprint(fgcc, "}\n")
 
 		// Dummy declaration for _cgo_main.c
-		fmt.Fprintf(fm, `char %s[1] __asm__("%s.%s");`, goName, gccgoSymbolPrefix, goName)
+		fmt.Fprintf(fm, `char %s[1] __asm__("%s.%s");`, goName, gccgoSymbolPrefix, gccgoToSymbol(goName))
 		fmt.Fprint(fm, "\n")
 
 		// For gccgo we use a wrapper function in Go, in order
@@ -1279,112 +1266,23 @@ func (p *Package) writeExportHeader(fgcch io.Writer) {
 	fmt.Fprintf(fgcch, "%s\n", p.gccExportHeaderProlog())
 }
 
-// gccgoUsesNewMangling reports whether gccgo uses the new collision-free
-// packagepath mangling scheme (see determineGccgoManglingScheme for more
-// info).
-func gccgoUsesNewMangling() bool {
-	if !gccgoMangleCheckDone {
-		gccgoNewmanglingInEffect = determineGccgoManglingScheme()
-		gccgoMangleCheckDone = true
-	}
-	return gccgoNewmanglingInEffect
-}
-
-const mangleCheckCode = `
-package läufer
-func Run(x int) int {
-  return 1
-}
-`
-
-// determineGccgoManglingScheme performs a runtime test to see which
-// flavor of packagepath mangling gccgo is using. Older versions of
-// gccgo use a simple mangling scheme where there can be collisions
-// between packages whose paths are different but mangle to the same
-// string. More recent versions of gccgo use a new mangler that avoids
-// these collisions. Return value is whether gccgo uses the new mangling.
-func determineGccgoManglingScheme() bool {
-
-	// Emit a small Go file for gccgo to compile.
-	filepat := "*_gccgo_manglecheck.go"
-	var f *os.File
-	var err error
-	if f, err = ioutil.TempFile(*objDir, filepat); err != nil {
-		fatalf("%v", err)
-	}
-	gofilename := f.Name()
-	defer os.Remove(gofilename)
-
-	if err = ioutil.WriteFile(gofilename, []byte(mangleCheckCode), 0666); err != nil {
-		fatalf("%v", err)
-	}
-
-	// Compile with gccgo, capturing generated assembly.
-	gccgocmd := os.Getenv("GCCGO")
-	if gccgocmd == "" {
-		gpath, gerr := exec.LookPath("gccgo")
-		if gerr != nil {
-			fatalf("unable to locate gccgo: %v", gerr)
-		}
-		gccgocmd = gpath
-	}
-	cmd := exec.Command(gccgocmd, "-S", "-o", "-", gofilename)
-	buf, cerr := cmd.CombinedOutput()
-	if cerr != nil {
-		fatalf("%s", cerr)
-	}
-
-	// New mangling: expect go.l..u00e4ufer.Run
-	// Old mangling: expect go.l__ufer.Run
-	return regexp.MustCompile(`go\.l\.\.u00e4ufer\.Run`).Match(buf)
-}
-
-// gccgoPkgpathToSymbolNew converts a package path to a gccgo-style
-// package symbol.
-func gccgoPkgpathToSymbolNew(ppath string) string {
-	bsl := []byte{}
-	changed := false
-	for _, c := range []byte(ppath) {
-		switch {
-		case 'A' <= c && c <= 'Z', 'a' <= c && c <= 'z',
-			'0' <= c && c <= '9', c == '_':
-			bsl = append(bsl, c)
-		case c == '.':
-			bsl = append(bsl, ".x2e"...)
-		default:
-			changed = true
-			encbytes := []byte(fmt.Sprintf("..z%02x", c))
-			bsl = append(bsl, encbytes...)
+// gccgoToSymbol converts a name to a mangled symbol for gccgo.
+func gccgoToSymbol(ppath string) string {
+	if gccgoMangler == nil {
+		var err error
+		cmd := os.Getenv("GCCGO")
+		if cmd == "" {
+			cmd, err = exec.LookPath("gccgo")
+			if err != nil {
+				fatalf("unable to locate gccgo: %v", err)
+			}
 		}
-	}
-	if !changed {
-		return ppath
-	}
-	return string(bsl)
-}
-
-// gccgoPkgpathToSymbolOld converts a package path to a gccgo-style
-// package symbol using the older mangling scheme.
-func gccgoPkgpathToSymbolOld(ppath string) string {
-	clean := func(r rune) rune {
-		switch {
-		case 'A' <= r && r <= 'Z', 'a' <= r && r <= 'z',
-			'0' <= r && r <= '9':
-			return r
+		gccgoMangler, err = pkgpath.ToSymbolFunc(cmd, *objDir)
+		if err != nil {
+			fatalf("%v", err)
 		}
-		return '_'
-	}
-	return strings.Map(clean, ppath)
-}
-
-// gccgoPkgpathToSymbol converts a package path to a mangled packagepath
-// symbol.
-func gccgoPkgpathToSymbol(ppath string) string {
-	if gccgoUsesNewMangling() {
-		return gccgoPkgpathToSymbolNew(ppath)
-	} else {
-		return gccgoPkgpathToSymbolOld(ppath)
 	}
+	return gccgoMangler(ppath)
 }
 
 // Return the package prefix when using gccgo.
@@ -1394,12 +1292,12 @@ func (p *Package) gccgoSymbolPrefix() string {
 	}
 
 	if *gccgopkgpath != "" {
-		return gccgoPkgpathToSymbol(*gccgopkgpath)
+		return gccgoToSymbol(*gccgopkgpath)
 	}
 	if *gccgoprefix == "" && p.PackageName == "main" {
 		return "main"
 	}
-	prefix := gccgoPkgpathToSymbol(*gccgoprefix)
+	prefix := gccgoToSymbol(*gccgoprefix)
 	if prefix == "" {
 		prefix = "go"
 	}
@@ -1663,9 +1561,6 @@ const goProlog = `
 //go:linkname _cgo_runtime_cgocall runtime.cgocall
 func _cgo_runtime_cgocall(unsafe.Pointer, uintptr) int32
 
-//go:linkname _cgo_runtime_cgocallback runtime.cgocallback
-func _cgo_runtime_cgocallback(unsafe.Pointer, unsafe.Pointer, uintptr, uintptr)
-
 //go:linkname _cgoCheckPointer runtime.cgoCheckPointer
 func _cgoCheckPointer(interface{}, interface{})
 
@@ -1791,8 +1686,12 @@ void _cgoPREFIX_Cfunc__Cmalloc(void *v) {
 `
 
 func (p *Package) cPrologGccgo() string {
-	return strings.Replace(strings.Replace(cPrologGccgo, "PREFIX", cPrefix, -1),
-		"GCCGOSYMBOLPREF", p.gccgoSymbolPrefix(), -1)
+	r := strings.NewReplacer(
+		"PREFIX", cPrefix,
+		"GCCGOSYMBOLPREF", p.gccgoSymbolPrefix(),
+		"_cgoCheckPointer", gccgoToSymbol("_cgoCheckPointer"),
+		"_cgoCheckResult", gccgoToSymbol("_cgoCheckResult"))
+	return r.Replace(cPrologGccgo)
 }
 
 const cPrologGccgo = `