cgo: mangle identifier names

This mangles CGo identifier names to something like "_Cgo_foo" instead
of using literal identifiers like "C.foo". This works around
golang/go#71777.

I don't like this solution, but I hope we'll find a better solution in
the future. In that case we can revert this commit.

Author: aykevl

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)
 			}

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},
@@ -423,15 +423,15 @@ 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
 		// instead of types such as C.int, which are used here.
 		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"