diff --git a/.circleci/config.yml b/.circleci/config.yml
index e2069e3485..a3a052c28c 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -109,9 +109,9 @@ jobs:
           # "make lint" fails before go 1.21 because internal/tools/go.mod specifies packages that require go 1.21
           fmt-check: false
     resource_class: large
-  test-llvm19-go123:
+  test-llvm19-go124:
     docker:
-      - image: golang:1.23-bullseye
+      - image: golang:1.24-bullseye
     steps:
       - test-linux:
           llvm: "19"
@@ -124,4 +124,4 @@ workflows:
       # least the smoke tests still pass.
       - test-llvm15-go119
       # This tests LLVM 19 support when linking against system libraries.
-      - test-llvm19-go123
+      - test-llvm19-go124
diff --git a/.github/workflows/build-macos.yml b/.github/workflows/build-macos.yml
index 07b0d307d0..25b5971783 100644
--- a/.github/workflows/build-macos.yml
+++ b/.github/workflows/build-macos.yml
@@ -39,7 +39,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Restore LLVM source cache
         uses: actions/cache/restore@v4
@@ -143,7 +143,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Build TinyGo (LLVM ${{ matrix.version }})
         run: go install -tags=llvm${{ matrix.version }}
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 139b7d03b7..3cbf33c6b0 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -18,7 +18,7 @@ jobs:
     # statically linked binary.
     runs-on: ubuntu-latest
     container:
-      image: golang:1.23-alpine
+      image: golang:1.24-alpine
     outputs:
       version: ${{ steps.version.outputs.version }}
     steps:
@@ -146,7 +146,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Install wasmtime
         uses: bytecodealliance/actions/wasmtime/setup@v1
@@ -189,7 +189,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Install Node.js
         uses: actions/setup-node@v4
@@ -315,7 +315,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Restore LLVM source cache
         uses: actions/cache/restore@v4
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index e1794ef13b..42365f59b7 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -41,7 +41,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Restore cached LLVM source
         uses: actions/cache/restore@v4
@@ -156,7 +156,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Download TinyGo build
         uses: actions/download-artifact@v4
@@ -186,7 +186,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Download TinyGo build
         uses: actions/download-artifact@v4
@@ -222,7 +222,7 @@ jobs:
       - name: Install Go
         uses: actions/setup-go@v5
         with:
-          go-version: '1.23'
+          go-version: '1.24'
           cache: true
       - name: Download TinyGo build
         uses: actions/download-artifact@v4
diff --git a/Dockerfile b/Dockerfile
index 9a9effac2b..520ad7c9b5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 # tinygo-llvm stage obtains the llvm source for TinyGo
-FROM golang:1.23 AS tinygo-llvm
+FROM golang:1.24 AS tinygo-llvm
 
 RUN apt-get update && \
     apt-get install -y apt-utils make cmake clang-15 ninja-build && \
@@ -33,7 +33,7 @@ RUN cd /tinygo/ && \
 
 # tinygo-compiler copies the compiler build over to a base Go container (without
 # all the build tools etc).
-FROM golang:1.23 AS tinygo-compiler
+FROM golang:1.24 AS tinygo-compiler
 
 # Copy tinygo build.
 COPY --from=tinygo-compiler-build /tinygo/build/release/tinygo /tinygo
diff --git a/GNUmakefile b/GNUmakefile
index 423a2a20e0..a13b8fc562 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -309,11 +309,9 @@ TEST_PACKAGES_FAST = \
 	container/heap \
 	container/list \
 	container/ring \
-	crypto/des \
 	crypto/ecdsa \
 	crypto/elliptic \
 	crypto/md5 \
-	crypto/rc4 \
 	crypto/sha1 \
 	crypto/sha256 \
 	crypto/sha512 \
@@ -355,17 +353,11 @@ TEST_PACKAGES_FAST = \
 	unique \
 	$(nil)
 
-# Assume this will go away before Go2, so only check minor version.
-ifeq ($(filter $(shell $(GO) env GOVERSION | cut -f 2 -d.), 16 17 18), )
-TEST_PACKAGES_FAST += crypto/internal/nistec/fiat
-else
-TEST_PACKAGES_FAST += crypto/elliptic/internal/fiat
-endif
-
 # archive/zip requires os.ReadAt, which is not yet supported on windows
 # bytes requires mmap
 # compress/flate appears to hang on wasi
 # crypto/aes fails on wasi, needs panic()/recover()
+# crypto/des fails on wasi, needs panic()/recover()
 # crypto/hmac fails on wasi, it exits with a "slice out of range" panic
 # debug/plan9obj requires os.ReadAt, which is not yet supported on windows
 # image requires recover(), which is not yet supported on wasi
@@ -386,6 +378,7 @@ TEST_PACKAGES_LINUX := \
 	archive/zip \
 	compress/flate \
 	crypto/aes \
+	crypto/des \
 	crypto/hmac \
 	debug/dwarf \
 	debug/plan9obj \
@@ -407,6 +400,7 @@ TEST_PACKAGES_DARWIN := $(TEST_PACKAGES_LINUX)
 
 TEST_PACKAGES_WINDOWS := \
 	compress/flate \
+	crypto/des \
 	crypto/hmac \
 	os/user \
 	strconv \
@@ -441,7 +435,7 @@ endif
 # TODO: parallelize, and only show failing tests (no implied -v flag).
 .PHONY: tinygo-test
 tinygo-test:
-	$(TINYGO) test $(TEST_PACKAGES_HOST) $(TEST_PACKAGES_SLOW)
+	$(TINYGO) test -v $(TEST_PACKAGES_HOST) $(TEST_PACKAGES_SLOW)
 	@# io/fs requires os.ReadDir, not yet supported on windows or wasi. It also
 	@# requires a large stack-size. Hence, io/fs is only run conditionally.
 	@# For more details, see the comments on issue #3143.
diff --git a/builder/config.go b/builder/config.go
index d1d0a2713b..b36b9333f3 100644
--- a/builder/config.go
+++ b/builder/config.go
@@ -26,7 +26,7 @@ func NewConfig(options *compileopts.Options) (*compileopts.Config, error) {
 
 	// Version range supported by TinyGo.
 	const minorMin = 19
-	const minorMax = 23
+	const minorMax = 24
 
 	// Check that we support this Go toolchain version.
 	gorootMajor, gorootMinor, err := goenv.GetGorootVersion()
@@ -36,7 +36,7 @@ func NewConfig(options *compileopts.Options) (*compileopts.Config, error) {
 	if gorootMajor != 1 || gorootMinor < minorMin || gorootMinor > minorMax {
 		// Note: when this gets updated, also update the Go compatibility matrix:
 		// https://github.com/tinygo-org/tinygo-site/blob/dev/content/docs/reference/go-compat-matrix.md
-		return nil, fmt.Errorf("requires go version 1.19 through 1.23, got go%d.%d", gorootMajor, gorootMinor)
+		return nil, fmt.Errorf("requires go version 1.%d through 1.%d, got go%d.%d", minorMin, minorMax, gorootMajor, gorootMinor)
 	}
 
 	// Check that the Go toolchain version isn't too new, if we haven't been
diff --git a/builder/sizes_test.go b/builder/sizes_test.go
index 2b2b08fe6f..a96ce9e6f6 100644
--- a/builder/sizes_test.go
+++ b/builder/sizes_test.go
@@ -44,7 +44,7 @@ func TestBinarySize(t *testing.T) {
 		// microcontrollers
 		{"hifive1b", "examples/echo", 4560, 280, 0, 2268},
 		{"microbit", "examples/serial", 2916, 388, 8, 2272},
-		{"wioterminal", "examples/pininterrupt", 7315, 1489, 116, 6912},
+		{"wioterminal", "examples/pininterrupt", 7359, 1489, 116, 6912},
 
 		// TODO: also check wasm. Right now this is difficult, because
 		// wasm binaries are run through wasm-opt and therefore the
diff --git a/cgo/cgo.go b/cgo/cgo.go
index cb822a38ec..6b8ea4373d 100644
--- a/cgo/cgo.go
+++ b/cgo/cgo.go
@@ -92,18 +92,18 @@ type noescapingFunc struct {
 // cgoAliases list type aliases between Go and C, for types that are equivalent
 // in both languages. See addTypeAliases.
 var cgoAliases = map[string]string{
-	"C.int8_t":    "int8",
-	"C.int16_t":   "int16",
-	"C.int32_t":   "int32",
-	"C.int64_t":   "int64",
-	"C.uint8_t":   "uint8",
-	"C.uint16_t":  "uint16",
-	"C.uint32_t":  "uint32",
-	"C.uint64_t":  "uint64",
-	"C.uintptr_t": "uintptr",
-	"C.float":     "float32",
-	"C.double":    "float64",
-	"C._Bool":     "bool",
+	"_Cgo_int8_t":    "int8",
+	"_Cgo_int16_t":   "int16",
+	"_Cgo_int32_t":   "int32",
+	"_Cgo_int64_t":   "int64",
+	"_Cgo_uint8_t":   "uint8",
+	"_Cgo_uint16_t":  "uint16",
+	"_Cgo_uint32_t":  "uint32",
+	"_Cgo_uint64_t":  "uint64",
+	"_Cgo_uintptr_t": "uintptr",
+	"_Cgo_float":     "float32",
+	"_Cgo_double":    "float64",
+	"_Cgo__Bool":     "bool",
 }
 
 // builtinAliases are handled specially because they only exist on the Go side
@@ -145,48 +145,46 @@ typedef unsigned long long  _Cgo_ulonglong;
 // The string/bytes functions below implement C.CString etc. To make sure the
 // runtime doesn't need to know the C int type, lengths are converted to uintptr
 // first.
-// These functions will be modified to get a "C." prefix, so the source below
-// doesn't reflect the final AST.
 const generatedGoFilePrefixBase = `
 import "syscall"
 import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func __GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func __GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func __CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func __get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 `
 
 const generatedGoFilePrefixOther = generatedGoFilePrefixBase + `
-func __get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 `
 
@@ -197,7 +195,7 @@ func __get_errno() error {
 // map the errno values to match the values in the syscall package.
 // Source of the errno values: lib/mingw-w64/mingw-w64-headers/crt/errno.h
 const generatedGoFilePrefixWindows = generatedGoFilePrefixBase + `
-var __errno_mapping = [...]syscall.Errno{
+var _Cgo___errno_mapping = [...]syscall.Errno{
 	1:  syscall.EPERM,
 	2:  syscall.ENOENT,
 	3:  syscall.ESRCH,
@@ -238,10 +236,10 @@ var __errno_mapping = [...]syscall.Errno{
 	42: syscall.EILSEQ,
 }
 
-func __get_errno() error {
-	num := C.__get_errno_num()
-	if num < uintptr(len(__errno_mapping)) {
-		if mapped := __errno_mapping[num]; mapped != 0 {
+func _Cgo___get_errno() error {
+	num := _Cgo___get_errno_num()
+	if num < uintptr(len(_Cgo___errno_mapping)) {
+		if mapped := _Cgo___errno_mapping[num]; mapped != 0 {
 			return mapped
 		}
 	}
@@ -304,23 +302,6 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 	// If the Comments field is not set to nil, the go/format package will get
 	// confused about where comments should go.
 	p.generated.Comments = nil
-	// Adjust some of the functions in there.
-	for _, decl := range p.generated.Decls {
-		switch decl := decl.(type) {
-		case *ast.FuncDecl:
-			switch decl.Name.Name {
-			case "CString", "GoString", "GoStringN", "__GoStringN", "GoBytes", "__GoBytes", "CBytes", "__CBytes", "__get_errno_num", "__get_errno", "__errno_mapping":
-				// Adjust the name to have a "C." prefix so it is correctly
-				// resolved.
-				decl.Name.Name = "C." + decl.Name.Name
-			}
-		}
-	}
-	// Patch some types, for example *C.char in C.CString.
-	cf := p.newCGoFile(nil, -1) // dummy *cgoFile for the walker
-	astutil.Apply(p.generated, func(cursor *astutil.Cursor) bool {
-		return cf.walker(cursor, nil)
-	}, nil)
 
 	// Find `import "C"` C fragments in the file.
 	p.cgoHeaders = make([]string, len(files)) // combined CGo header fragment for each file
@@ -399,7 +380,7 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 			Tok:    token.TYPE,
 		}
 		for _, name := range builtinAliases {
-			typeSpec := p.getIntegerType("C."+name, names["_Cgo_"+name])
+			typeSpec := p.getIntegerType("_Cgo_"+name, names["_Cgo_"+name])
 			gen.Specs = append(gen.Specs, typeSpec)
 		}
 		p.generated.Decls = append(p.generated.Decls, gen)
@@ -1272,7 +1253,7 @@ func (p *cgoPackage) getUnnamedDeclName(prefix string, itf interface{}) string {
 func (f *cgoFile) getASTDeclName(name string, found clangCursor, iscall bool) string {
 	// Some types are defined in stdint.h and map directly to a particular Go
 	// type.
-	if alias := cgoAliases["C."+name]; alias != "" {
+	if alias := cgoAliases["_Cgo_"+name]; alias != "" {
 		return alias
 	}
 	node := f.getASTDeclNode(name, found)
@@ -1282,7 +1263,7 @@ func (f *cgoFile) getASTDeclName(name string, found clangCursor, iscall bool) st
 		}
 		return node.Name.Name
 	}
-	return "C." + name
+	return "_Cgo_" + name
 }
 
 // getASTDeclNode will declare the given C AST node (if not already defined) and
@@ -1382,8 +1363,8 @@ extern __typeof(%s) %s __attribute__((alias(%#v)));
 	case *elaboratedTypeInfo:
 		// Add struct bitfields.
 		for _, bitfield := range elaboratedType.bitfields {
-			f.createBitfieldGetter(bitfield, "C."+name)
-			f.createBitfieldSetter(bitfield, "C."+name)
+			f.createBitfieldGetter(bitfield, "_Cgo_"+name)
+			f.createBitfieldSetter(bitfield, "_Cgo_"+name)
 		}
 		if elaboratedType.unionSize != 0 {
 			// Create union getters/setters.
@@ -1392,7 +1373,7 @@ extern __typeof(%s) %s __attribute__((alias(%#v)));
 					f.addError(elaboratedType.pos, fmt.Sprintf("union must have field with a single name, it has %d names", len(field.Names)))
 					continue
 				}
-				f.createUnionAccessor(field, "C."+name)
+				f.createUnionAccessor(field, "_Cgo_"+name)
 			}
 		}
 	}
@@ -1441,7 +1422,7 @@ func (f *cgoFile) walker(cursor *astutil.Cursor, names map[string]clangCursor) b
 			node.Rhs = append(node.Rhs, &ast.CallExpr{
 				Fun: &ast.Ident{
 					NamePos: node.Lhs[1].End(),
-					Name:    "C.__get_errno",
+					Name:    "_Cgo___get_errno",
 				},
 			})
 		}
@@ -1466,7 +1447,7 @@ func (f *cgoFile) walker(cursor *astutil.Cursor, names map[string]clangCursor) b
 			return true
 		}
 		if x.Name == "C" {
-			name := "C." + node.Sel.Name
+			name := "_Cgo_" + node.Sel.Name
 			if found, ok := names[node.Sel.Name]; ok {
 				name = f.getASTDeclName(node.Sel.Name, found, false)
 			}
diff --git a/cgo/libclang.go b/cgo/libclang.go
index 4da77ff6e7..759417a6ea 100644
--- a/cgo/libclang.go
+++ b/cgo/libclang.go
@@ -219,7 +219,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		numArgs := int(C.tinygo_clang_Cursor_getNumArguments(c))
 		obj := &ast.Object{
 			Kind: ast.Fun,
-			Name: "C." + name,
+			Name: "_Cgo_" + name,
 		}
 		exportName := name
 		localName := name
@@ -257,7 +257,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 			},
 			Name: &ast.Ident{
 				NamePos: pos,
-				Name:    "C." + localName,
+				Name:    "_Cgo_" + localName,
 				Obj:     obj,
 			},
 			Type: &ast.FuncType{
@@ -319,7 +319,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		return decl, stringSignature
 	case C.CXCursor_StructDecl, C.CXCursor_UnionDecl:
 		typ := f.makeASTRecordType(c, pos)
-		typeName := "C." + name
+		typeName := "_Cgo_" + name
 		typeExpr := typ.typeExpr
 		if typ.unionSize != 0 {
 			// Convert to a single-field struct type.
@@ -340,7 +340,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		obj.Decl = typeSpec
 		return typeSpec, typ
 	case C.CXCursor_TypedefDecl:
-		typeName := "C." + name
+		typeName := "_Cgo_" + name
 		underlyingType := C.tinygo_clang_getTypedefDeclUnderlyingType(c)
 		obj := &ast.Object{
 			Kind: ast.Typ,
@@ -378,12 +378,12 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		}
 		obj := &ast.Object{
 			Kind: ast.Var,
-			Name: "C." + name,
+			Name: "_Cgo_" + name,
 		}
 		valueSpec := &ast.ValueSpec{
 			Names: []*ast.Ident{{
 				NamePos: pos,
-				Name:    "C." + name,
+				Name:    "_Cgo_" + name,
 				Obj:     obj,
 			}},
 			Type: typeExpr,
@@ -407,12 +407,12 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		}
 		obj := &ast.Object{
 			Kind: ast.Con,
-			Name: "C." + name,
+			Name: "_Cgo_" + name,
 		}
 		valueSpec := &ast.ValueSpec{
 			Names: []*ast.Ident{{
 				NamePos: pos,
-				Name:    "C." + name,
+				Name:    "_Cgo_" + name,
 				Obj:     obj,
 			}},
 			Values: []ast.Expr{expr},
@@ -423,7 +423,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 	case C.CXCursor_EnumDecl:
 		obj := &ast.Object{
 			Kind: ast.Typ,
-			Name: "C." + name,
+			Name: "_Cgo_" + name,
 		}
 		underlying := C.tinygo_clang_getEnumDeclIntegerType(c)
 		// TODO: gc's CGo implementation uses types such as `uint32` for enums
@@ -431,7 +431,7 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		typeSpec := &ast.TypeSpec{
 			Name: &ast.Ident{
 				NamePos: pos,
-				Name:    "C." + name,
+				Name:    "_Cgo_" + name,
 				Obj:     obj,
 			},
 			Assign: pos,
@@ -454,12 +454,12 @@ func (f *cgoFile) createASTNode(name string, c clangCursor) (ast.Node, any) {
 		}
 		obj := &ast.Object{
 			Kind: ast.Con,
-			Name: "C." + name,
+			Name: "_Cgo_" + name,
 		}
 		valueSpec := &ast.ValueSpec{
 			Names: []*ast.Ident{{
 				NamePos: pos,
-				Name:    "C." + name,
+				Name:    "_Cgo_" + name,
 				Obj:     obj,
 			}},
 			Values: []ast.Expr{expr},
@@ -745,27 +745,27 @@ func (f *cgoFile) makeASTType(typ C.CXType, pos token.Pos) ast.Expr {
 	var typeName string
 	switch typ.kind {
 	case C.CXType_Char_S, C.CXType_Char_U:
-		typeName = "C.char"
+		typeName = "_Cgo_char"
 	case C.CXType_SChar:
-		typeName = "C.schar"
+		typeName = "_Cgo_schar"
 	case C.CXType_UChar:
-		typeName = "C.uchar"
+		typeName = "_Cgo_uchar"
 	case C.CXType_Short:
-		typeName = "C.short"
+		typeName = "_Cgo_short"
 	case C.CXType_UShort:
-		typeName = "C.ushort"
+		typeName = "_Cgo_ushort"
 	case C.CXType_Int:
-		typeName = "C.int"
+		typeName = "_Cgo_int"
 	case C.CXType_UInt:
-		typeName = "C.uint"
+		typeName = "_Cgo_uint"
 	case C.CXType_Long:
-		typeName = "C.long"
+		typeName = "_Cgo_long"
 	case C.CXType_ULong:
-		typeName = "C.ulong"
+		typeName = "_Cgo_ulong"
 	case C.CXType_LongLong:
-		typeName = "C.longlong"
+		typeName = "_Cgo_longlong"
 	case C.CXType_ULongLong:
-		typeName = "C.ulonglong"
+		typeName = "_Cgo_ulonglong"
 	case C.CXType_Bool:
 		typeName = "bool"
 	case C.CXType_Float, C.CXType_Double, C.CXType_LongDouble:
@@ -896,7 +896,7 @@ func (f *cgoFile) makeASTType(typ C.CXType, pos token.Pos) ast.Expr {
 		typeSpelling := getString(C.clang_getTypeSpelling(typ))
 		typeKindSpelling := getString(C.clang_getTypeKindSpelling(typ.kind))
 		f.addError(pos, fmt.Sprintf("unknown C type: %v (libclang type kind %s)", typeSpelling, typeKindSpelling))
-		typeName = "C.<unknown>"
+		typeName = "_Cgo_<unknown>"
 	}
 	return &ast.Ident{
 		NamePos: pos,
@@ -913,7 +913,7 @@ func (p *cgoPackage) getIntegerType(name string, cursor clangCursor) *ast.TypeSp
 	var goName string
 	typeSize := C.clang_Type_getSizeOf(underlyingType)
 	switch name {
-	case "C.char":
+	case "_Cgo_char":
 		if typeSize != 1 {
 			// This happens for some very special purpose architectures
 			// (DSPs etc.) that are not currently targeted.
@@ -926,7 +926,7 @@ func (p *cgoPackage) getIntegerType(name string, cursor clangCursor) *ast.TypeSp
 		case C.CXType_Char_U:
 			goName = "uint8"
 		}
-	case "C.schar", "C.short", "C.int", "C.long", "C.longlong":
+	case "_Cgo_schar", "_Cgo_short", "_Cgo_int", "_Cgo_long", "_Cgo_longlong":
 		switch typeSize {
 		case 1:
 			goName = "int8"
@@ -937,7 +937,7 @@ func (p *cgoPackage) getIntegerType(name string, cursor clangCursor) *ast.TypeSp
 		case 8:
 			goName = "int64"
 		}
-	case "C.uchar", "C.ushort", "C.uint", "C.ulong", "C.ulonglong":
+	case "_Cgo_uchar", "_Cgo_ushort", "_Cgo_uint", "_Cgo_ulong", "_Cgo_ulonglong":
 		switch typeSize {
 		case 1:
 			goName = "uint8"
diff --git a/cgo/testdata/basic.out.go b/cgo/testdata/basic.out.go
index 7348ee3791..191cfba38f 100644
--- a/cgo/testdata/basic.out.go
+++ b/cgo/testdata/basic.out.go
@@ -5,50 +5,50 @@ import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func C.CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func C.GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func C.__GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func C.GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func C.__GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func C.__CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func C.CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func C.__get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 
-func C.__get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 
 type (
-	C.char      uint8
-	C.schar     int8
-	C.uchar     uint8
-	C.short     int16
-	C.ushort    uint16
-	C.int       int32
-	C.uint      uint32
-	C.long      int32
-	C.ulong     uint32
-	C.longlong  int64
-	C.ulonglong uint64
+	_Cgo_char      uint8
+	_Cgo_schar     int8
+	_Cgo_uchar     uint8
+	_Cgo_short     int16
+	_Cgo_ushort    uint16
+	_Cgo_int       int32
+	_Cgo_uint      uint32
+	_Cgo_long      int32
+	_Cgo_ulong     uint32
+	_Cgo_longlong  int64
+	_Cgo_ulonglong uint64
 )
diff --git a/cgo/testdata/const.out.go b/cgo/testdata/const.out.go
index 21705afc4f..0329ba5985 100644
--- a/cgo/testdata/const.out.go
+++ b/cgo/testdata/const.out.go
@@ -5,58 +5,58 @@ import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func C.CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func C.GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func C.__GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func C.GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func C.__GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func C.__CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func C.CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func C.__get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 
-func C.__get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 
 type (
-	C.char      uint8
-	C.schar     int8
-	C.uchar     uint8
-	C.short     int16
-	C.ushort    uint16
-	C.int       int32
-	C.uint      uint32
-	C.long      int32
-	C.ulong     uint32
-	C.longlong  int64
-	C.ulonglong uint64
+	_Cgo_char      uint8
+	_Cgo_schar     int8
+	_Cgo_uchar     uint8
+	_Cgo_short     int16
+	_Cgo_ushort    uint16
+	_Cgo_int       int32
+	_Cgo_uint      uint32
+	_Cgo_long      int32
+	_Cgo_ulong     uint32
+	_Cgo_longlong  int64
+	_Cgo_ulonglong uint64
 )
 
-const C.foo = 3
-const C.bar = C.foo
-const C.unreferenced = 4
-const C.referenced = C.unreferenced
-const C.fnlike_val = 5
-const C.square_val = (20 * 20)
-const C.add_val = (3 + 5)
+const _Cgo_foo = 3
+const _Cgo_bar = _Cgo_foo
+const _Cgo_unreferenced = 4
+const _Cgo_referenced = _Cgo_unreferenced
+const _Cgo_fnlike_val = 5
+const _Cgo_square_val = (20 * 20)
+const _Cgo_add_val = (3 + 5)
diff --git a/cgo/testdata/errors.out.go b/cgo/testdata/errors.out.go
index e0f7d1f541..0ae794087f 100644
--- a/cgo/testdata/errors.out.go
+++ b/cgo/testdata/errors.out.go
@@ -14,16 +14,16 @@
 //     testdata/errors.go:3:1: function "unusedFunction" in #cgo noescape line is not used
 
 // Type checking errors after CGo processing:
-//     testdata/errors.go:102: cannot use 2 << 10 (untyped int constant 2048) as C.char value in variable declaration (overflows)
+//     testdata/errors.go:102: cannot use 2 << 10 (untyped int constant 2048) as _Cgo_char value in variable declaration (overflows)
 //     testdata/errors.go:105: unknown field z in struct literal
-//     testdata/errors.go:108: undefined: C.SOME_CONST_1
-//     testdata/errors.go:110: cannot use C.SOME_CONST_3 (untyped int constant 1234) as byte value in variable declaration (overflows)
-//     testdata/errors.go:112: undefined: C.SOME_CONST_4
-//     testdata/errors.go:114: undefined: C.SOME_CONST_b
-//     testdata/errors.go:116: undefined: C.SOME_CONST_startspace
-//     testdata/errors.go:119: undefined: C.SOME_PARAM_CONST_invalid
-//     testdata/errors.go:122: undefined: C.add_toomuch
-//     testdata/errors.go:123: undefined: C.add_toolittle
+//     testdata/errors.go:108: undefined: _Cgo_SOME_CONST_1
+//     testdata/errors.go:110: cannot use _Cgo_SOME_CONST_3 (untyped int constant 1234) as byte value in variable declaration (overflows)
+//     testdata/errors.go:112: undefined: _Cgo_SOME_CONST_4
+//     testdata/errors.go:114: undefined: _Cgo_SOME_CONST_b
+//     testdata/errors.go:116: undefined: _Cgo_SOME_CONST_startspace
+//     testdata/errors.go:119: undefined: _Cgo_SOME_PARAM_CONST_invalid
+//     testdata/errors.go:122: undefined: _Cgo_add_toomuch
+//     testdata/errors.go:123: undefined: _Cgo_add_toolittle
 
 package main
 
@@ -32,58 +32,58 @@ import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func C.CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func C.GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func C.__GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func C.GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func C.__GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func C.__CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func C.CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func C.__get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 
-func C.__get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 
 type (
-	C.char      uint8
-	C.schar     int8
-	C.uchar     uint8
-	C.short     int16
-	C.ushort    uint16
-	C.int       int32
-	C.uint      uint32
-	C.long      int32
-	C.ulong     uint32
-	C.longlong  int64
-	C.ulonglong uint64
+	_Cgo_char      uint8
+	_Cgo_schar     int8
+	_Cgo_uchar     uint8
+	_Cgo_short     int16
+	_Cgo_ushort    uint16
+	_Cgo_int       int32
+	_Cgo_uint      uint32
+	_Cgo_long      int32
+	_Cgo_ulong     uint32
+	_Cgo_longlong  int64
+	_Cgo_ulonglong uint64
 )
-type C.struct_point_t struct {
-	x C.int
-	y C.int
+type _Cgo_struct_point_t struct {
+	x _Cgo_int
+	y _Cgo_int
 }
-type C.point_t = C.struct_point_t
+type _Cgo_point_t = _Cgo_struct_point_t
 
-const C.SOME_CONST_3 = 1234
-const C.SOME_PARAM_CONST_valid = 3 + 4
+const _Cgo_SOME_CONST_3 = 1234
+const _Cgo_SOME_PARAM_CONST_valid = 3 + 4
diff --git a/cgo/testdata/flags.out.go b/cgo/testdata/flags.out.go
index 8662412296..ac5cf546db 100644
--- a/cgo/testdata/flags.out.go
+++ b/cgo/testdata/flags.out.go
@@ -10,53 +10,53 @@ import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func C.CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func C.GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func C.__GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func C.GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func C.__GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func C.__CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func C.CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func C.__get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 
-func C.__get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 
 type (
-	C.char      uint8
-	C.schar     int8
-	C.uchar     uint8
-	C.short     int16
-	C.ushort    uint16
-	C.int       int32
-	C.uint      uint32
-	C.long      int32
-	C.ulong     uint32
-	C.longlong  int64
-	C.ulonglong uint64
+	_Cgo_char      uint8
+	_Cgo_schar     int8
+	_Cgo_uchar     uint8
+	_Cgo_short     int16
+	_Cgo_ushort    uint16
+	_Cgo_int       int32
+	_Cgo_uint      uint32
+	_Cgo_long      int32
+	_Cgo_ulong     uint32
+	_Cgo_longlong  int64
+	_Cgo_ulonglong uint64
 )
 
-const C.BAR = 3
-const C.FOO_H = 1
+const _Cgo_BAR = 3
+const _Cgo_FOO_H = 1
diff --git a/cgo/testdata/symbols.out.go b/cgo/testdata/symbols.out.go
index 2ca80c1e65..8a603cfd7e 100644
--- a/cgo/testdata/symbols.out.go
+++ b/cgo/testdata/symbols.out.go
@@ -5,80 +5,80 @@ import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func C.CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func C.GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func C.__GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func C.GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func C.__GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func C.__CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func C.CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func C.__get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 
-func C.__get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 
 type (
-	C.char      uint8
-	C.schar     int8
-	C.uchar     uint8
-	C.short     int16
-	C.ushort    uint16
-	C.int       int32
-	C.uint      uint32
-	C.long      int32
-	C.ulong     uint32
-	C.longlong  int64
-	C.ulonglong uint64
+	_Cgo_char      uint8
+	_Cgo_schar     int8
+	_Cgo_uchar     uint8
+	_Cgo_short     int16
+	_Cgo_ushort    uint16
+	_Cgo_int       int32
+	_Cgo_uint      uint32
+	_Cgo_long      int32
+	_Cgo_ulong     uint32
+	_Cgo_longlong  int64
+	_Cgo_ulonglong uint64
 )
 
 //export foo
-func C.foo(a C.int, b C.int) C.int
+func _Cgo_foo(a _Cgo_int, b _Cgo_int) _Cgo_int
 
-var C.foo$funcaddr unsafe.Pointer
+var _Cgo_foo$funcaddr unsafe.Pointer
 
 //export variadic0
 //go:variadic
-func C.variadic0()
+func _Cgo_variadic0()
 
-var C.variadic0$funcaddr unsafe.Pointer
+var _Cgo_variadic0$funcaddr unsafe.Pointer
 
 //export variadic2
 //go:variadic
-func C.variadic2(x C.int, y C.int)
+func _Cgo_variadic2(x _Cgo_int, y _Cgo_int)
 
-var C.variadic2$funcaddr unsafe.Pointer
+var _Cgo_variadic2$funcaddr unsafe.Pointer
 
 //export _Cgo_static_173c95a79b6df1980521_staticfunc
-func C.staticfunc!symbols.go(x C.int)
+func _Cgo_staticfunc!symbols.go(x _Cgo_int)
 
-var C.staticfunc!symbols.go$funcaddr unsafe.Pointer
+var _Cgo_staticfunc!symbols.go$funcaddr unsafe.Pointer
 
 //export notEscapingFunction
 //go:noescape
-func C.notEscapingFunction(a *C.int)
+func _Cgo_notEscapingFunction(a *_Cgo_int)
 
-var C.notEscapingFunction$funcaddr unsafe.Pointer
+var _Cgo_notEscapingFunction$funcaddr unsafe.Pointer
 //go:extern someValue
-var C.someValue C.int
+var _Cgo_someValue _Cgo_int
diff --git a/cgo/testdata/types.out.go b/cgo/testdata/types.out.go
index b3fe414b07..3eaa53f1fb 100644
--- a/cgo/testdata/types.out.go
+++ b/cgo/testdata/types.out.go
@@ -5,158 +5,162 @@ import "unsafe"
 
 var _ unsafe.Pointer
 
-//go:linkname C.CString runtime.cgo_CString
-func C.CString(string) *C.char
+//go:linkname _Cgo_CString runtime.cgo_CString
+func _Cgo_CString(string) *_Cgo_char
 
-//go:linkname C.GoString runtime.cgo_GoString
-func C.GoString(*C.char) string
+//go:linkname _Cgo_GoString runtime.cgo_GoString
+func _Cgo_GoString(*_Cgo_char) string
 
-//go:linkname C.__GoStringN runtime.cgo_GoStringN
-func C.__GoStringN(*C.char, uintptr) string
+//go:linkname _Cgo___GoStringN runtime.cgo_GoStringN
+func _Cgo___GoStringN(*_Cgo_char, uintptr) string
 
-func C.GoStringN(cstr *C.char, length C.int) string {
-	return C.__GoStringN(cstr, uintptr(length))
+func _Cgo_GoStringN(cstr *_Cgo_char, length _Cgo_int) string {
+	return _Cgo___GoStringN(cstr, uintptr(length))
 }
 
-//go:linkname C.__GoBytes runtime.cgo_GoBytes
-func C.__GoBytes(unsafe.Pointer, uintptr) []byte
+//go:linkname _Cgo___GoBytes runtime.cgo_GoBytes
+func _Cgo___GoBytes(unsafe.Pointer, uintptr) []byte
 
-func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
-	return C.__GoBytes(ptr, uintptr(length))
+func _Cgo_GoBytes(ptr unsafe.Pointer, length _Cgo_int) []byte {
+	return _Cgo___GoBytes(ptr, uintptr(length))
 }
 
-//go:linkname C.__CBytes runtime.cgo_CBytes
-func C.__CBytes([]byte) unsafe.Pointer
+//go:linkname _Cgo___CBytes runtime.cgo_CBytes
+func _Cgo___CBytes([]byte) unsafe.Pointer
 
-func C.CBytes(b []byte) unsafe.Pointer {
-	return C.__CBytes(b)
+func _Cgo_CBytes(b []byte) unsafe.Pointer {
+	return _Cgo___CBytes(b)
 }
 
-//go:linkname C.__get_errno_num runtime.cgo_errno
-func C.__get_errno_num() uintptr
+//go:linkname _Cgo___get_errno_num runtime.cgo_errno
+func _Cgo___get_errno_num() uintptr
 
-func C.__get_errno() error {
-	return syscall.Errno(C.__get_errno_num())
+func _Cgo___get_errno() error {
+	return syscall.Errno(_Cgo___get_errno_num())
 }
 
 type (
-	C.char      uint8
-	C.schar     int8
-	C.uchar     uint8
-	C.short     int16
-	C.ushort    uint16
-	C.int       int32
-	C.uint      uint32
-	C.long      int32
-	C.ulong     uint32
-	C.longlong  int64
-	C.ulonglong uint64
+	_Cgo_char      uint8
+	_Cgo_schar     int8
+	_Cgo_uchar     uint8
+	_Cgo_short     int16
+	_Cgo_ushort    uint16
+	_Cgo_int       int32
+	_Cgo_uint      uint32
+	_Cgo_long      int32
+	_Cgo_ulong     uint32
+	_Cgo_longlong  int64
+	_Cgo_ulonglong uint64
 )
-type C.myint = C.int
-type C.struct_point2d_t struct {
-	x C.int
-	y C.int
-}
-type C.point2d_t = C.struct_point2d_t
-type C.struct_point3d struct {
-	x C.int
-	y C.int
-	z C.int
-}
-type C.point3d_t = C.struct_point3d
-type C.struct_type1 struct {
-	_type   C.int
-	__type  C.int
-	___type C.int
-}
-type C.struct_type2 struct{ _type C.int }
-type C.union_union1_t struct{ i C.int }
-type C.union1_t = C.union_union1_t
-type C.union_union3_t struct{ $union uint64 }
-
-func (union *C.union_union3_t) unionfield_i() *C.int { return (*C.int)(unsafe.Pointer(&union.$union)) }
-func (union *C.union_union3_t) unionfield_d() *float64 {
+type _Cgo_myint = _Cgo_int
+type _Cgo_struct_point2d_t struct {
+	x _Cgo_int
+	y _Cgo_int
+}
+type _Cgo_point2d_t = _Cgo_struct_point2d_t
+type _Cgo_struct_point3d struct {
+	x _Cgo_int
+	y _Cgo_int
+	z _Cgo_int
+}
+type _Cgo_point3d_t = _Cgo_struct_point3d
+type _Cgo_struct_type1 struct {
+	_type   _Cgo_int
+	__type  _Cgo_int
+	___type _Cgo_int
+}
+type _Cgo_struct_type2 struct{ _type _Cgo_int }
+type _Cgo_union_union1_t struct{ i _Cgo_int }
+type _Cgo_union1_t = _Cgo_union_union1_t
+type _Cgo_union_union3_t struct{ $union uint64 }
+
+func (union *_Cgo_union_union3_t) unionfield_i() *_Cgo_int {
+	return (*_Cgo_int)(unsafe.Pointer(&union.$union))
+}
+func (union *_Cgo_union_union3_t) unionfield_d() *float64 {
 	return (*float64)(unsafe.Pointer(&union.$union))
 }
-func (union *C.union_union3_t) unionfield_s() *C.short {
-	return (*C.short)(unsafe.Pointer(&union.$union))
+func (union *_Cgo_union_union3_t) unionfield_s() *_Cgo_short {
+	return (*_Cgo_short)(unsafe.Pointer(&union.$union))
 }
 
-type C.union3_t = C.union_union3_t
-type C.union_union2d struct{ $union [2]uint64 }
+type _Cgo_union3_t = _Cgo_union_union3_t
+type _Cgo_union_union2d struct{ $union [2]uint64 }
 
-func (union *C.union_union2d) unionfield_i() *C.int { return (*C.int)(unsafe.Pointer(&union.$union)) }
-func (union *C.union_union2d) unionfield_d() *[2]float64 {
+func (union *_Cgo_union_union2d) unionfield_i() *_Cgo_int {
+	return (*_Cgo_int)(unsafe.Pointer(&union.$union))
+}
+func (union *_Cgo_union_union2d) unionfield_d() *[2]float64 {
 	return (*[2]float64)(unsafe.Pointer(&union.$union))
 }
 
-type C.union2d_t = C.union_union2d
-type C.union_unionarray_t struct{ arr [10]C.uchar }
-type C.unionarray_t = C.union_unionarray_t
-type C._Ctype_union___0 struct{ $union [3]uint32 }
+type _Cgo_union2d_t = _Cgo_union_union2d
+type _Cgo_union_unionarray_t struct{ arr [10]_Cgo_uchar }
+type _Cgo_unionarray_t = _Cgo_union_unionarray_t
+type _Cgo__Ctype_union___0 struct{ $union [3]uint32 }
 
-func (union *C._Ctype_union___0) unionfield_area() *C.point2d_t {
-	return (*C.point2d_t)(unsafe.Pointer(&union.$union))
+func (union *_Cgo__Ctype_union___0) unionfield_area() *_Cgo_point2d_t {
+	return (*_Cgo_point2d_t)(unsafe.Pointer(&union.$union))
 }
-func (union *C._Ctype_union___0) unionfield_solid() *C.point3d_t {
-	return (*C.point3d_t)(unsafe.Pointer(&union.$union))
+func (union *_Cgo__Ctype_union___0) unionfield_solid() *_Cgo_point3d_t {
+	return (*_Cgo_point3d_t)(unsafe.Pointer(&union.$union))
 }
 
-type C.struct_struct_nested_t struct {
-	begin C.point2d_t
-	end   C.point2d_t
-	tag   C.int
+type _Cgo_struct_struct_nested_t struct {
+	begin _Cgo_point2d_t
+	end   _Cgo_point2d_t
+	tag   _Cgo_int
 
-	coord C._Ctype_union___0
+	coord _Cgo__Ctype_union___0
 }
-type C.struct_nested_t = C.struct_struct_nested_t
-type C.union_union_nested_t struct{ $union [2]uint64 }
+type _Cgo_struct_nested_t = _Cgo_struct_struct_nested_t
+type _Cgo_union_union_nested_t struct{ $union [2]uint64 }
 
-func (union *C.union_union_nested_t) unionfield_point() *C.point3d_t {
-	return (*C.point3d_t)(unsafe.Pointer(&union.$union))
+func (union *_Cgo_union_union_nested_t) unionfield_point() *_Cgo_point3d_t {
+	return (*_Cgo_point3d_t)(unsafe.Pointer(&union.$union))
 }
-func (union *C.union_union_nested_t) unionfield_array() *C.unionarray_t {
-	return (*C.unionarray_t)(unsafe.Pointer(&union.$union))
+func (union *_Cgo_union_union_nested_t) unionfield_array() *_Cgo_unionarray_t {
+	return (*_Cgo_unionarray_t)(unsafe.Pointer(&union.$union))
 }
-func (union *C.union_union_nested_t) unionfield_thing() *C.union3_t {
-	return (*C.union3_t)(unsafe.Pointer(&union.$union))
+func (union *_Cgo_union_union_nested_t) unionfield_thing() *_Cgo_union3_t {
+	return (*_Cgo_union3_t)(unsafe.Pointer(&union.$union))
 }
 
-type C.union_nested_t = C.union_union_nested_t
-type C.enum_option = C.int
-type C.option_t = C.enum_option
-type C.enum_option2_t = C.uint
-type C.option2_t = C.enum_option2_t
-type C.struct_types_t struct {
+type _Cgo_union_nested_t = _Cgo_union_union_nested_t
+type _Cgo_enum_option = _Cgo_int
+type _Cgo_option_t = _Cgo_enum_option
+type _Cgo_enum_option2_t = _Cgo_uint
+type _Cgo_option2_t = _Cgo_enum_option2_t
+type _Cgo_struct_types_t struct {
 	f   float32
 	d   float64
-	ptr *C.int
+	ptr *_Cgo_int
 }
-type C.types_t = C.struct_types_t
-type C.myIntArray = [10]C.int
-type C.struct_bitfield_t struct {
-	start        C.uchar
-	__bitfield_1 C.uchar
+type _Cgo_types_t = _Cgo_struct_types_t
+type _Cgo_myIntArray = [10]_Cgo_int
+type _Cgo_struct_bitfield_t struct {
+	start        _Cgo_uchar
+	__bitfield_1 _Cgo_uchar
 
-	d C.uchar
-	e C.uchar
+	d _Cgo_uchar
+	e _Cgo_uchar
 }
 
-func (s *C.struct_bitfield_t) bitfield_a() C.uchar { return s.__bitfield_1 & 0x1f }
-func (s *C.struct_bitfield_t) set_bitfield_a(value C.uchar) {
+func (s *_Cgo_struct_bitfield_t) bitfield_a() _Cgo_uchar { return s.__bitfield_1 & 0x1f }
+func (s *_Cgo_struct_bitfield_t) set_bitfield_a(value _Cgo_uchar) {
 	s.__bitfield_1 = s.__bitfield_1&^0x1f | value&0x1f<<0
 }
-func (s *C.struct_bitfield_t) bitfield_b() C.uchar {
+func (s *_Cgo_struct_bitfield_t) bitfield_b() _Cgo_uchar {
 	return s.__bitfield_1 >> 5 & 0x1
 }
-func (s *C.struct_bitfield_t) set_bitfield_b(value C.uchar) {
+func (s *_Cgo_struct_bitfield_t) set_bitfield_b(value _Cgo_uchar) {
 	s.__bitfield_1 = s.__bitfield_1&^0x20 | value&0x1<<5
 }
-func (s *C.struct_bitfield_t) bitfield_c() C.uchar {
+func (s *_Cgo_struct_bitfield_t) bitfield_c() _Cgo_uchar {
 	return s.__bitfield_1 >> 6
 }
-func (s *C.struct_bitfield_t) set_bitfield_c(value C.uchar,
+func (s *_Cgo_struct_bitfield_t) set_bitfield_c(value _Cgo_uchar,
 
 ) { s.__bitfield_1 = s.__bitfield_1&0x3f | value<<6 }
 
-type C.bitfield_t = C.struct_bitfield_t
+type _Cgo_bitfield_t = _Cgo_struct_bitfield_t
diff --git a/compiler/alias.go b/compiler/alias.go
index b0191a7a11..9d57a587e7 100644
--- a/compiler/alias.go
+++ b/compiler/alias.go
@@ -18,11 +18,12 @@ var stdlibAliases = map[string]string{
 	// crypto packages
 	"crypto/ed25519/internal/edwards25519/field.feMul": "crypto/ed25519/internal/edwards25519/field.feMulGeneric",
 	"crypto/internal/edwards25519/field.feSquare":      "crypto/ed25519/internal/edwards25519/field.feSquareGeneric",
-	"crypto/md5.block":         "crypto/md5.blockGeneric",
-	"crypto/sha1.block":        "crypto/sha1.blockGeneric",
-	"crypto/sha1.blockAMD64":   "crypto/sha1.blockGeneric",
-	"crypto/sha256.block":      "crypto/sha256.blockGeneric",
-	"crypto/sha512.blockAMD64": "crypto/sha512.blockGeneric",
+	"crypto/md5.block":           "crypto/md5.blockGeneric",
+	"crypto/sha1.block":          "crypto/sha1.blockGeneric",
+	"crypto/sha1.blockAMD64":     "crypto/sha1.blockGeneric",
+	"crypto/sha256.block":        "crypto/sha256.blockGeneric",
+	"crypto/sha512.blockAMD64":   "crypto/sha512.blockGeneric",
+	"internal/chacha8rand.block": "internal/chacha8rand.block_generic",
 
 	// AES
 	"crypto/aes.decryptBlockAsm": "crypto/aes.decryptBlock",
diff --git a/compiler/symbol.go b/compiler/symbol.go
index 5ecf68e54a..1de3c6f39d 100644
--- a/compiler/symbol.go
+++ b/compiler/symbol.go
@@ -432,9 +432,8 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
 			// pass for C variadic functions. This includes both explicit
 			// (with ...) and implicit (no parameters in signature)
 			// functions.
-			if strings.HasPrefix(f.Name(), "C.") {
-				// This prefix cannot naturally be created, it must have
-				// been created as a result of CGo preprocessing.
+			if strings.HasPrefix(f.Name(), "_Cgo_") {
+				// This prefix was created as a result of CGo preprocessing.
 				info.variadic = true
 			}
 		}
diff --git a/src/internal/abi/type.go b/src/internal/abi/type.go
new file mode 100644
index 0000000000..d1853e0f3d
--- /dev/null
+++ b/src/internal/abi/type.go
@@ -0,0 +1,7 @@
+package abi
+
+type Type struct {
+	// Intentionally left empty. TinyGo uses a different way to represent types,
+	// so this is unimplementable. The type definition here is purely for
+	// compatibility.
+}
diff --git a/src/internal/task/task.go b/src/internal/task/task.go
index 546f5ba117..58c02fe846 100644
--- a/src/internal/task/task.go
+++ b/src/internal/task/task.go
@@ -21,6 +21,9 @@ type Task struct {
 	// state is the underlying running state of the task.
 	state state
 
+	// This is needed for some crypto packages.
+	FipsIndicator uint8
+
 	// DeferFrame stores a pointer to the (stack allocated) defer frame of the
 	// goroutine that is used for the recover builtin.
 	DeferFrame unsafe.Pointer
diff --git a/src/machine/flash.go b/src/machine/flash.go
index 716fc4a53b..da832afdb8 100644
--- a/src/machine/flash.go
+++ b/src/machine/flash.go
@@ -64,3 +64,14 @@ type BlockDevice interface {
 	// EraseBlockSize to map addresses to blocks.
 	EraseBlocks(start, len int64) error
 }
+
+// pad data if needed so it is long enough for correct byte alignment on writes.
+func flashPad(p []byte, writeBlockSize int) []byte {
+	overflow := len(p) % writeBlockSize
+	if overflow != 0 {
+		for i := 0; i < writeBlockSize-overflow; i++ {
+			p = append(p, 0xff)
+		}
+	}
+	return p
+}
diff --git a/src/machine/machine_atsamd21.go b/src/machine/machine_atsamd21.go
index 3d0abc0fa8..0a5c320ca0 100644
--- a/src/machine/machine_atsamd21.go
+++ b/src/machine/machine_atsamd21.go
@@ -7,7 +7,6 @@
 package machine
 
 import (
-	"bytes"
 	"device/arm"
 	"device/sam"
 	"errors"
@@ -1917,7 +1916,7 @@ func (f flashBlockDevice) WriteAt(p []byte, off int64) (n int, err error) {
 	f.ensureInitComplete()
 
 	address := FlashDataStart() + uintptr(off)
-	padded := f.pad(p)
+	padded := flashPad(p, int(f.WriteBlockSize()))
 
 	waitWhileFlashBusy()
 
@@ -1992,17 +1991,6 @@ func (f flashBlockDevice) EraseBlocks(start, len int64) error {
 	return nil
 }
 
-// pad data if needed so it is long enough for correct byte alignment on writes.
-func (f flashBlockDevice) pad(p []byte) []byte {
-	overflow := int64(len(p)) % f.WriteBlockSize()
-	if overflow == 0 {
-		return p
-	}
-
-	padding := bytes.Repeat([]byte{0xff}, int(f.WriteBlockSize()-overflow))
-	return append(p, padding...)
-}
-
 func (f flashBlockDevice) ensureInitComplete() {
 	if f.initComplete {
 		return
diff --git a/src/machine/machine_atsamd51.go b/src/machine/machine_atsamd51.go
index bcaaec7212..5cd1d314a2 100644
--- a/src/machine/machine_atsamd51.go
+++ b/src/machine/machine_atsamd51.go
@@ -7,7 +7,6 @@
 package machine
 
 import (
-	"bytes"
 	"device/arm"
 	"device/sam"
 	"errors"
@@ -2174,7 +2173,7 @@ func (f flashBlockDevice) WriteAt(p []byte, off int64) (n int, err error) {
 	}
 
 	address := FlashDataStart() + uintptr(off)
-	padded := f.pad(p)
+	padded := flashPad(p, int(f.WriteBlockSize()))
 
 	settings := disableFlashCache()
 	defer restoreFlashCache(settings)
@@ -2263,17 +2262,6 @@ func (f flashBlockDevice) EraseBlocks(start, len int64) error {
 	return nil
 }
 
-// pad data if needed so it is long enough for correct byte alignment on writes.
-func (f flashBlockDevice) pad(p []byte) []byte {
-	overflow := int64(len(p)) % f.WriteBlockSize()
-	if overflow == 0 {
-		return p
-	}
-
-	padding := bytes.Repeat([]byte{0xff}, int(f.WriteBlockSize()-overflow))
-	return append(p, padding...)
-}
-
 func disableFlashCache() uint16 {
 	settings := sam.NVMCTRL.CTRLA.Get()
 
diff --git a/src/machine/machine_nrf.go b/src/machine/machine_nrf.go
index 4da6645352..d6d6349f29 100644
--- a/src/machine/machine_nrf.go
+++ b/src/machine/machine_nrf.go
@@ -3,7 +3,6 @@
 package machine
 
 import (
-	"bytes"
 	"device/nrf"
 	"internal/binary"
 	"runtime/interrupt"
@@ -386,7 +385,7 @@ func (f flashBlockDevice) WriteAt(p []byte, off int64) (n int, err error) {
 	}
 
 	address := FlashDataStart() + uintptr(off)
-	padded := f.pad(p)
+	padded := flashPad(p, int(f.WriteBlockSize()))
 
 	waitWhileFlashBusy()
 
@@ -444,17 +443,6 @@ func (f flashBlockDevice) EraseBlocks(start, len int64) error {
 	return nil
 }
 
-// pad data if needed so it is long enough for correct byte alignment on writes.
-func (f flashBlockDevice) pad(p []byte) []byte {
-	overflow := int64(len(p)) % f.WriteBlockSize()
-	if overflow == 0 {
-		return p
-	}
-
-	padding := bytes.Repeat([]byte{0xff}, int(f.WriteBlockSize()-overflow))
-	return append(p, padding...)
-}
-
 func waitWhileFlashBusy() {
 	for nrf.NVMC.GetREADY() != nrf.NVMC_READY_READY_Ready {
 	}
diff --git a/src/machine/machine_rp2040_flash.go b/src/machine/machine_rp2040_flash.go
index 8ee881e19a..1317c0926a 100644
--- a/src/machine/machine_rp2040_flash.go
+++ b/src/machine/machine_rp2040_flash.go
@@ -3,7 +3,6 @@
 package machine
 
 import (
-	"bytes"
 	"unsafe"
 )
 
@@ -101,17 +100,6 @@ func (f flashBlockDevice) EraseBlocks(start, length int64) error {
 	return f.eraseBlocks(start, length)
 }
 
-// pad data if needed so it is long enough for correct byte alignment on writes.
-func (f flashBlockDevice) pad(p []byte) []byte {
-	overflow := int64(len(p)) % f.WriteBlockSize()
-	if overflow == 0 {
-		return p
-	}
-
-	padding := bytes.Repeat([]byte{0xff}, int(f.WriteBlockSize()-overflow))
-	return append(p, padding...)
-}
-
 // return the correct address to be used for write
 func writeAddress(off int64) uintptr {
 	return readAddress(off) - uintptr(memoryStart)
diff --git a/src/machine/machine_rp2040_rom.go b/src/machine/machine_rp2040_rom.go
index eea461882d..5541e2a9bf 100644
--- a/src/machine/machine_rp2040_rom.go
+++ b/src/machine/machine_rp2040_rom.go
@@ -230,7 +230,7 @@ func (f flashBlockDevice) writeAt(p []byte, off int64) (n int, err error) {
 	// e.g. real address 0x10003000 is written to at
 	// 0x00003000
 	address := writeAddress(off)
-	padded := f.pad(p)
+	padded := flashPad(p, int(f.WriteBlockSize()))
 
 	C.flash_range_write(C.uint32_t(address),
 		(*C.uint8_t)(unsafe.Pointer(&padded[0])),
diff --git a/src/machine/machine_stm32_flash.go b/src/machine/machine_stm32_flash.go
index 710aa05d00..280dc8987e 100644
--- a/src/machine/machine_stm32_flash.go
+++ b/src/machine/machine_stm32_flash.go
@@ -5,7 +5,6 @@ package machine
 import (
 	"device/stm32"
 
-	"bytes"
 	"unsafe"
 )
 
@@ -41,7 +40,8 @@ func (f flashBlockDevice) WriteAt(p []byte, off int64) (n int, err error) {
 	unlockFlash()
 	defer lockFlash()
 
-	return writeFlashData(FlashDataStart()+uintptr(off), f.pad(p))
+	p = flashPad(p, int(f.WriteBlockSize()))
+	return writeFlashData(FlashDataStart()+uintptr(off), p)
 }
 
 // Size returns the number of bytes in this block device.
@@ -90,17 +90,6 @@ func (f flashBlockDevice) EraseBlocks(start, len int64) error {
 	return nil
 }
 
-// pad data if needed so it is long enough for correct byte alignment on writes.
-func (f flashBlockDevice) pad(p []byte) []byte {
-	overflow := int64(len(p)) % f.WriteBlockSize()
-	if overflow == 0 {
-		return p
-	}
-
-	padding := bytes.Repeat([]byte{0xff}, int(f.WriteBlockSize()-overflow))
-	return append(p, padding...)
-}
-
 const memoryStart = 0x08000000
 
 func unlockFlash() {
diff --git a/src/machine/usb/descriptor/hid.go b/src/machine/usb/descriptor/hid.go
index ea65f1ed97..06b9801530 100644
--- a/src/machine/usb/descriptor/hid.go
+++ b/src/machine/usb/descriptor/hid.go
@@ -1,9 +1,9 @@
 package descriptor
 
 import (
-	"bytes"
 	"errors"
 	"internal/binary"
+	"internal/bytealg"
 )
 
 var configurationCDCHID = [configurationTypeLen]byte{
@@ -87,7 +87,7 @@ func FindClassHIDType(des, class []byte) (ClassHIDType, error) {
 
 	// search only for ClassHIDType without the ClassLength,
 	// in case it has already been set.
-	idx := bytes.Index(des, class[:ClassHIDTypeLen-2])
+	idx := bytealg.Index(des, class[:ClassHIDTypeLen-2])
 	if idx == -1 {
 		return ClassHIDType{}, errNoClassHIDFound
 	}
diff --git a/src/os/file.go b/src/os/file.go
index 0e20d1bf10..e7dd214b73 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -318,6 +318,17 @@ func (f *File) Chmod(mode FileMode) (err error) {
 	return
 }
 
+// Chdir changes the current working directory to the file, which must be a
+// directory. If there is an error, it will be of type *PathError.
+func (f *File) Chdir() (err error) {
+	if f.handle == nil {
+		err = ErrClosed
+	} else {
+		err = f.chdir()
+	}
+	return
+}
+
 // LinkError records an error during a link or symlink or rename system call and
 // the paths that caused it.
 type LinkError struct {
diff --git a/src/os/file_other.go b/src/os/file_other.go
index 75c0332817..8e7d33e00e 100644
--- a/src/os/file_other.go
+++ b/src/os/file_other.go
@@ -42,6 +42,12 @@ func NewFile(fd uintptr, name string) *File {
 	return &File{&file{handle: stdioFileHandle(fd), name: name}}
 }
 
+// Chdir changes the current working directory to the named directory.
+// If there is an error, it will be of type *PathError.
+func Chdir(dir string) error {
+	return ErrNotImplemented
+}
+
 // Rename renames (moves) oldpath to newpath.
 // If newpath already exists and is not a directory, Rename replaces it.
 // OS-specific restrictions may apply when oldpath and newpath are in different directories.
@@ -153,3 +159,7 @@ func (f *File) Truncate(size int64) (err error) {
 func (f *File) chmod(mode FileMode) error {
 	return ErrUnsupported
 }
+
+func (f *File) chdir() error {
+	return ErrNotImplemented
+}
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index fd4d464f5b..9dc3a91e09 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -166,6 +166,22 @@ func (f *File) chmod(mode FileMode) error {
 	return nil
 }
 
+func (f *File) chdir() error {
+	if f.handle == nil {
+		return ErrClosed
+	}
+
+	// TODO: use syscall.Fchdir instead
+	longName := fixLongPath(f.name)
+	e := ignoringEINTR(func() error {
+		return syscall.Chdir(longName)
+	})
+	if e != nil {
+		return &PathError{Op: "chdir", Path: f.name, Err: e}
+	}
+	return nil
+}
+
 // ReadAt reads up to len(b) bytes from the File starting at the given absolute offset.
 // It returns the number of bytes read and any error encountered, possibly io.EOF.
 // At end of file, Pread returns 0, io.EOF.
diff --git a/src/os/file_windows.go b/src/os/file_windows.go
index 022381deed..50c5ee7a82 100644
--- a/src/os/file_windows.go
+++ b/src/os/file_windows.go
@@ -146,3 +146,7 @@ func isWindowsNulName(name string) bool {
 func (f *File) chmod(mode FileMode) error {
 	return ErrNotImplemented
 }
+
+func (f *File) chdir() error {
+	return ErrNotImplemented
+}
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 69b57fd1cc..7ac71aa184 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -271,6 +271,10 @@ func (v Value) Comparable() bool {
 	}
 }
 
+func (v Value) Equal(u Value) bool {
+	panic("unimplemented: reflect.Value.Equal")
+}
+
 func (v Value) Addr() Value {
 	if !v.CanAddr() {
 		panic("reflect.Value.Addr of unaddressable value")
diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index ec33a4469c..9ae1f982b9 100644
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -226,3 +226,8 @@ func divideByZeroPanic() {
 func blockingPanic() {
 	runtimePanicAt(returnAddress(0), "trying to do blocking operation in exported function")
 }
+
+//go:linkname fips_fatal crypto/internal/fips140.fatal
+func fips_fatal(msg string) {
+	runtimePanic(msg)
+}
diff --git a/src/runtime/scheduler.go b/src/runtime/scheduler.go
index 727c7f5f2c..40740da310 100644
--- a/src/runtime/scheduler.go
+++ b/src/runtime/scheduler.go
@@ -31,3 +31,14 @@ func scheduleLogChan(msg string, ch *channel, t *task.Task) {
 func Goexit() {
 	panicOrGoexit(nil, panicGoexit)
 }
+
+//go:linkname fips_getIndicator crypto/internal/fips140.getIndicator
+func fips_getIndicator() uint8 {
+	return task.Current().FipsIndicator
+}
+
+//go:linkname fips_setIndicator crypto/internal/fips140.setIndicator
+func fips_setIndicator(indicator uint8) {
+	// This indicator is stored per goroutine.
+	task.Current().FipsIndicator = indicator
+}
diff --git a/src/runtime/synctest.go b/src/runtime/synctest.go
new file mode 100644
index 0000000000..fa11c991fc
--- /dev/null
+++ b/src/runtime/synctest.go
@@ -0,0 +1,15 @@
+package runtime
+
+// Dummy implementation of synctest functions (we don't support synctest at the
+// moment).
+
+//go:linkname synctest_acquire internal/synctest.acquire
+func synctest_acquire() any {
+	// Dummy: we don't support synctest.
+	return nil
+}
+
+//go:linkname synctest_release internal/synctest.release
+func synctest_release(sg any) {
+	// Dummy: we don't support synctest.
+}
diff --git a/src/runtime/time.go b/src/runtime/time.go
index 50bf61cf3c..3935b4486e 100644
--- a/src/runtime/time.go
+++ b/src/runtime/time.go
@@ -1,5 +1,18 @@
 package runtime
 
+//go:linkname time_runtimeNano time.runtimeNano
+func time_runtimeNano() int64 {
+	// Note: we're ignoring sync groups here (package testing/synctest).
+	// See: https://github.com/golang/go/issues/67434
+	return nanotime()
+}
+
+//go:linkname time_runtimeNow time.runtimeNow
+func time_runtimeNow() (sec int64, nsec int32, mono int64) {
+	// Also ignoring the sync group here, like time_runtimeNano above.
+	return now()
+}
+
 // timerNode is an element in a linked list of timers.
 type timerNode struct {
 	next     *timerNode
diff --git a/src/syscall/syscall_libc.go b/src/syscall/syscall_libc.go
index 0ef9784283..86c756383e 100644
--- a/src/syscall/syscall_libc.go
+++ b/src/syscall/syscall_libc.go
@@ -233,6 +233,10 @@ func (w WaitStatus) Continued() bool    { return false }
 func (w WaitStatus) StopSignal() Signal { return 0 }
 func (w WaitStatus) TrapCause() int     { return 0 }
 
+// Purely here for compatibility.
+type Rusage struct {
+}
+
 // since rusage is quite a big struct and we stub it out anyway no need to define it here
 func Wait4(pid int, wstatus *WaitStatus, options int, rusage uintptr) (wpid int, err error) {
 	return 0, ENOSYS // TODO
diff --git a/src/syscall/syscall_libc_wasi.go b/src/syscall/syscall_libc_wasi.go
index bbf81cd059..479377877b 100644
--- a/src/syscall/syscall_libc_wasi.go
+++ b/src/syscall/syscall_libc_wasi.go
@@ -120,8 +120,11 @@ const (
 	SYS_FCNTL64
 	SYS_FSTATAT64
 	SYS_IOCTL
+	SYS_MKDIRAT
 	SYS_OPENAT
+	SYS_READLINKAT
 	SYS_UNLINKAT
+	SYS_WAITID
 	PATH_MAX = 4096
 )
 
@@ -438,6 +441,13 @@ type RawSockaddrInet6 struct {
 	// stub
 }
 
+func RandomGet(b []byte) error {
+	if len(b) > 0 {
+		libc_arc4random_buf(unsafe.Pointer(&b[0]), uint(len(b)))
+	}
+	return nil
+}
+
 // This is a stub, it is not functional.
 func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
 
@@ -483,3 +493,8 @@ func libc_fdclosedir(unsafe.Pointer) int32
 //
 //export readdir
 func libc_readdir(unsafe.Pointer) *Dirent
+
+// void arc4random_buf(void *buf, size_t buflen);
+//
+//export arc4random_buf
+func libc_arc4random_buf(buf unsafe.Pointer, buflen uint)
diff --git a/src/testing/testing.go b/src/testing/testing.go
index cd19ada710..121f24ccf7 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -17,6 +17,7 @@ import (
 	"io/fs"
 	"math/rand"
 	"os"
+	"path/filepath"
 	"runtime"
 	"strconv"
 	"strings"
@@ -390,6 +391,49 @@ func (c *common) Setenv(key, value string) {
 	}
 }
 
+// Chdir calls os.Chdir(dir) and uses Cleanup to restore the current
+// working directory to its original value after the test. On Unix, it
+// also sets PWD environment variable for the duration of the test.
+//
+// Because Chdir affects the whole process, it cannot be used
+// in parallel tests or tests with parallel ancestors.
+func (c *common) Chdir(dir string) {
+	// Note: function copied from the Go 1.24.0 source tree.
+
+	oldwd, err := os.Open(".")
+	if err != nil {
+		c.Fatal(err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		c.Fatal(err)
+	}
+	// On POSIX platforms, PWD represents “an absolute pathname of the
+	// current working directory.” Since we are changing the working
+	// directory, we should also set or update PWD to reflect that.
+	switch runtime.GOOS {
+	case "windows", "plan9":
+		// Windows and Plan 9 do not use the PWD variable.
+	default:
+		if !filepath.IsAbs(dir) {
+			dir, err = os.Getwd()
+			if err != nil {
+				c.Fatal(err)
+			}
+		}
+		c.Setenv("PWD", dir)
+	}
+	c.Cleanup(func() {
+		err := oldwd.Chdir()
+		oldwd.Close()
+		if err != nil {
+			// It's not safe to continue with tests if we can't
+			// get back to the original working directory. Since
+			// we are holding a dirfd, this is highly unlikely.
+			panic("testing.Chdir: " + err.Error())
+		}
+	})
+}
+
 // runCleanup is called at the end of the test.
 func (c *common) runCleanup() {
 	for {