tinygo/cgo/cgo.go
Ayke van Laethem dfa713040a cgo: add support for enum types
Enum types are implemented as named types (with possible accompanying
typedefs as type aliases). The constants inside the enums are treated as
Go constants like in the Go toolchain.
2019-05-17 19:37:20 +02:00

695 строки
17 КиБ
Go

// Package cgo implements CGo by modifying a loaded AST. It does this by parsing
// the `import "C"` statements found in the source code with libclang and
// generating stub function and global declarations.
//
// There are a few advantages to modifying the AST directly instead of doing CGo
// as a preprocessing step, with the main advantage being that debug information
// is kept intact as much as possible.
package cgo
// This file extracts the `import "C"` statement from the source and modifies
// the AST for CGo. It does not use libclang directly: see libclang.go for the C
// source file parsing.
import (
"go/ast"
"go/token"
"sort"
"strconv"
"strings"
"golang.org/x/tools/go/ast/astutil"
)
// cgoPackage holds all CGo-related information of a package.
type cgoPackage struct {
generated *ast.File
generatedPos token.Pos
errors []error
dir string
fset *token.FileSet
tokenFiles map[string]*token.File
missingSymbols map[string]struct{}
constants map[string]constantInfo
functions map[string]*functionInfo
globals map[string]globalInfo
typedefs map[string]*typedefInfo
elaboratedTypes map[string]*elaboratedTypeInfo
enums map[string]enumInfo
}
// constantInfo stores some information about a CGo constant found by libclang
// and declared in the Go AST.
type constantInfo struct {
expr *ast.BasicLit
pos token.Pos
}
// functionInfo stores some information about a CGo function found by libclang
// and declared in the AST.
type functionInfo struct {
args []paramInfo
results *ast.FieldList
pos token.Pos
}
// paramInfo is a parameter of a CGo function (see functionInfo).
type paramInfo struct {
name string
typeExpr ast.Expr
}
// typedefInfo contains information about a single typedef in C.
type typedefInfo struct {
typeExpr ast.Expr
pos token.Pos
}
// elaboratedTypeInfo contains some information about an elaborated type
// (struct, union) found in the C AST.
type elaboratedTypeInfo struct {
typeExpr ast.Expr
pos token.Pos
}
// enumInfo contains information about an enum in the C.
type enumInfo struct {
typeExpr ast.Expr
pos token.Pos
}
// globalInfo contains information about a declared global variable in C.
type globalInfo struct {
typeExpr ast.Expr
pos token.Pos
}
// 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",
}
// builtinAliases are handled specially because they only exist on the Go side
// of CGo, not on the CGo side (they're prefixed with "_Cgo_" there).
var builtinAliases = map[string]struct{}{
"char": struct{}{},
"schar": struct{}{},
"uchar": struct{}{},
"short": struct{}{},
"ushort": struct{}{},
"int": struct{}{},
"uint": struct{}{},
"long": struct{}{},
"ulong": struct{}{},
"longlong": struct{}{},
"ulonglong": struct{}{},
}
// cgoTypes lists some C types with ambiguous sizes that must be retrieved
// somehow from C. This is done by adding some typedefs to get the size of each
// type.
const cgoTypes = `
typedef char _Cgo_char;
typedef signed char _Cgo_schar;
typedef unsigned char _Cgo_uchar;
typedef short _Cgo_short;
typedef unsigned short _Cgo_ushort;
typedef int _Cgo_int;
typedef unsigned int _Cgo_uint;
typedef long _Cgo_long;
typedef unsigned long _Cgo_ulong;
typedef long long _Cgo_longlong;
typedef unsigned long long _Cgo_ulonglong;
`
// Process extracts `import "C"` statements from the AST, parses the comment
// with libclang, and modifies the AST to use this information. It returns a
// newly created *ast.File that should be added to the list of to-be-parsed
// files. If there is one or more error, it returns these in the []error slice
// but still modifies the AST.
func Process(files []*ast.File, dir string, fset *token.FileSet, cflags []string) (*ast.File, []error) {
p := &cgoPackage{
dir: dir,
fset: fset,
tokenFiles: map[string]*token.File{},
missingSymbols: map[string]struct{}{},
constants: map[string]constantInfo{},
functions: map[string]*functionInfo{},
globals: map[string]globalInfo{},
typedefs: map[string]*typedefInfo{},
elaboratedTypes: map[string]*elaboratedTypeInfo{},
enums: map[string]enumInfo{},
}
// Add a new location for the following file.
generatedTokenPos := p.fset.AddFile(dir+"/!cgo.go", -1, 0)
generatedTokenPos.SetLines([]int{0})
p.generatedPos = generatedTokenPos.Pos(0)
// Construct a new in-memory AST for CGo declarations of this package.
unsafeImport := &ast.ImportSpec{
Path: &ast.BasicLit{
ValuePos: p.generatedPos,
Kind: token.STRING,
Value: "\"unsafe\"",
},
EndPos: p.generatedPos,
}
p.generated = &ast.File{
Package: p.generatedPos,
Name: &ast.Ident{
NamePos: p.generatedPos,
Name: files[0].Name.Name,
},
Decls: []ast.Decl{
&ast.GenDecl{
TokPos: p.generatedPos,
Tok: token.IMPORT,
Specs: []ast.Spec{
unsafeImport,
},
},
},
Imports: []*ast.ImportSpec{unsafeImport},
}
// Find all C.* symbols.
for _, f := range files {
astutil.Apply(f, p.findMissingCGoNames, nil)
}
for name := range builtinAliases {
p.missingSymbols["_Cgo_"+name] = struct{}{}
}
// Find `import "C"` statements in the file.
for _, f := range files {
for i := 0; i < len(f.Decls); i++ {
decl := f.Decls[i]
genDecl, ok := decl.(*ast.GenDecl)
if !ok {
continue
}
if len(genDecl.Specs) != 1 {
continue
}
spec, ok := genDecl.Specs[0].(*ast.ImportSpec)
if !ok {
continue
}
path, err := strconv.Unquote(spec.Path.Value)
if err != nil {
panic("could not parse import path: " + err.Error())
}
if path != "C" {
continue
}
cgoComment := genDecl.Doc.Text()
pos := genDecl.Pos()
if genDecl.Doc != nil {
pos = genDecl.Doc.Pos()
}
position := fset.PositionFor(pos, true)
p.parseFragment(cgoComment+cgoTypes, cflags, position.Filename, position.Line)
// Remove this import declaration.
f.Decls = append(f.Decls[:i], f.Decls[i+1:]...)
i--
}
// Print the AST, for debugging.
//ast.Print(fset, f)
}
// Declare functions found by libclang.
p.addFuncDecls()
// Declare stub function pointer values found by libclang.
p.addFuncPtrDecls()
// Declare globals found by libclang.
p.addConstDecls()
// Declare globals found by libclang.
p.addVarDecls()
// Forward C types to Go types (like C.uint32_t -> uint32).
p.addTypeAliases()
// Add type declarations for C types, declared using typedef in C.
p.addTypedefs()
// Add elaborated types for C structs and unions.
p.addElaboratedTypes()
// Add enum types and enum constants for C enums.
p.addEnumTypes()
// Patch the AST to use the declared types and functions.
for _, f := range files {
astutil.Apply(f, p.walker, nil)
}
// Print the newly generated in-memory AST, for debugging.
//ast.Print(fset, p.generated)
return p.generated, p.errors
}
// addFuncDecls adds the C function declarations found by libclang in the
// comment above the `import "C"` statement.
func (p *cgoPackage) addFuncDecls() {
names := make([]string, 0, len(p.functions))
for name := range p.functions {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
fn := p.functions[name]
obj := &ast.Object{
Kind: ast.Fun,
Name: "C." + name,
}
args := make([]*ast.Field, len(fn.args))
decl := &ast.FuncDecl{
Name: &ast.Ident{
NamePos: fn.pos,
Name: "C." + name,
Obj: obj,
},
Type: &ast.FuncType{
Func: fn.pos,
Params: &ast.FieldList{
Opening: fn.pos,
List: args,
Closing: fn.pos,
},
Results: fn.results,
},
}
obj.Decl = decl
for i, arg := range fn.args {
args[i] = &ast.Field{
Names: []*ast.Ident{
&ast.Ident{
NamePos: fn.pos,
Name: arg.name,
Obj: &ast.Object{
Kind: ast.Var,
Name: arg.name,
Decl: decl,
},
},
},
Type: arg.typeExpr,
}
}
p.generated.Decls = append(p.generated.Decls, decl)
}
}
// addFuncPtrDecls creates stub declarations of function pointer values. These
// values will later be replaced with the real values in the compiler.
// It adds code like the following to the AST:
//
// var (
// C.add unsafe.Pointer
// C.mul unsafe.Pointer
// // ...
// )
func (p *cgoPackage) addFuncPtrDecls() {
if len(p.functions) == 0 {
return
}
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.VAR,
Lparen: token.NoPos,
Rparen: token.NoPos,
}
names := make([]string, 0, len(p.functions))
for name := range p.functions {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
fn := p.functions[name]
obj := &ast.Object{
Kind: ast.Typ,
Name: "C." + name + "$funcaddr",
}
valueSpec := &ast.ValueSpec{
Names: []*ast.Ident{&ast.Ident{
NamePos: fn.pos,
Name: "C." + name + "$funcaddr",
Obj: obj,
}},
Type: &ast.SelectorExpr{
X: &ast.Ident{
NamePos: fn.pos,
Name: "unsafe",
},
Sel: &ast.Ident{
NamePos: fn.pos,
Name: "Pointer",
},
},
}
obj.Decl = valueSpec
gen.Specs = append(gen.Specs, valueSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
// addConstDecls declares external C constants in the Go source.
// It adds code like the following to the AST:
//
// const (
// C.CONST_INT = 5
// C.CONST_FLOAT = 5.8
// // ...
// )
func (p *cgoPackage) addConstDecls() {
if len(p.constants) == 0 {
return
}
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.CONST,
Lparen: token.NoPos,
Rparen: token.NoPos,
}
names := make([]string, 0, len(p.constants))
for name := range p.constants {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
constVal := p.constants[name]
obj := &ast.Object{
Kind: ast.Con,
Name: "C." + name,
}
valueSpec := &ast.ValueSpec{
Names: []*ast.Ident{&ast.Ident{
NamePos: constVal.pos,
Name: "C." + name,
Obj: obj,
}},
Values: []ast.Expr{constVal.expr},
}
obj.Decl = valueSpec
gen.Specs = append(gen.Specs, valueSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
// addVarDecls declares external C globals in the Go source.
// It adds code like the following to the AST:
//
// var (
// C.globalInt int
// C.globalBool bool
// // ...
// )
func (p *cgoPackage) addVarDecls() {
if len(p.globals) == 0 {
return
}
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.VAR,
Lparen: token.NoPos,
Rparen: token.NoPos,
}
names := make([]string, 0, len(p.globals))
for name := range p.globals {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
global := p.globals[name]
obj := &ast.Object{
Kind: ast.Var,
Name: "C." + name,
}
valueSpec := &ast.ValueSpec{
Names: []*ast.Ident{&ast.Ident{
NamePos: global.pos,
Name: "C." + name,
Obj: obj,
}},
Type: global.typeExpr,
}
obj.Decl = valueSpec
gen.Specs = append(gen.Specs, valueSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
// addTypeAliases aliases some built-in Go types with their equivalent C types.
// It adds code like the following to the AST:
//
// type (
// C.int8_t = int8
// C.int16_t = int16
// // ...
// )
func (p *cgoPackage) addTypeAliases() {
aliasKeys := make([]string, 0, len(cgoAliases))
for key := range cgoAliases {
aliasKeys = append(aliasKeys, key)
}
sort.Strings(aliasKeys)
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.TYPE,
Lparen: token.NoPos,
Rparen: token.NoPos,
}
for _, typeName := range aliasKeys {
goTypeName := cgoAliases[typeName]
obj := &ast.Object{
Kind: ast.Typ,
Name: typeName,
}
typeSpec := &ast.TypeSpec{
Name: &ast.Ident{
NamePos: token.NoPos,
Name: typeName,
Obj: obj,
},
Assign: p.generatedPos,
Type: &ast.Ident{
NamePos: token.NoPos,
Name: goTypeName,
},
}
obj.Decl = typeSpec
gen.Specs = append(gen.Specs, typeSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
func (p *cgoPackage) addTypedefs() {
if len(p.typedefs) == 0 {
return
}
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.TYPE,
}
names := make([]string, 0, len(p.typedefs))
for name := range p.typedefs {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
typedef := p.typedefs[name]
typeName := "C." + name
isAlias := true
if strings.HasPrefix(name, "_Cgo_") {
typeName = "C." + name[len("_Cgo_"):]
isAlias = false // C.short etc. should not be aliased to the equivalent Go type (not portable)
}
if _, ok := cgoAliases[typeName]; ok {
// This is a type that also exists in Go (defined in stdint.h).
continue
}
obj := &ast.Object{
Kind: ast.Typ,
Name: typeName,
}
typeSpec := &ast.TypeSpec{
Name: &ast.Ident{
NamePos: typedef.pos,
Name: typeName,
Obj: obj,
},
Type: typedef.typeExpr,
}
if isAlias {
typeSpec.Assign = typedef.pos
}
obj.Decl = typeSpec
gen.Specs = append(gen.Specs, typeSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
// addElaboratedTypes adds C elaborated types as aliases. These are the "struct
// foo" or "union foo" types, often used in a typedef.
//
// See also:
// https://en.cppreference.com/w/cpp/language/elaborated_type_specifier
func (p *cgoPackage) addElaboratedTypes() {
if len(p.elaboratedTypes) == 0 {
return
}
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.TYPE,
}
names := make([]string, 0, len(p.elaboratedTypes))
for name := range p.elaboratedTypes {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
typ := p.elaboratedTypes[name]
typeName := "C." + name
obj := &ast.Object{
Kind: ast.Typ,
Name: typeName,
}
typeSpec := &ast.TypeSpec{
Name: &ast.Ident{
NamePos: typ.pos,
Name: typeName,
Obj: obj,
},
Type: typ.typeExpr,
}
obj.Decl = typeSpec
gen.Specs = append(gen.Specs, typeSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
// addEnumTypes adds C enums to the AST. For example, the following C code:
//
// enum option {
// optionA,
// optionB = 5,
// };
//
// is translated to the following Go code equivalent:
//
// type C.enum_option int32
//
// The constants are treated just like macros so are inserted into the AST by
// addConstDecls.
// See also: https://en.cppreference.com/w/c/language/enum
func (p *cgoPackage) addEnumTypes() {
if len(p.enums) == 0 {
return
}
gen := &ast.GenDecl{
TokPos: token.NoPos,
Tok: token.TYPE,
}
names := make([]string, 0, len(p.enums))
for name := range p.enums {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
typ := p.enums[name]
typeName := "C.enum_" + name
obj := &ast.Object{
Kind: ast.Typ,
Name: typeName,
}
typeSpec := &ast.TypeSpec{
Name: &ast.Ident{
NamePos: typ.pos,
Name: typeName,
Obj: obj,
},
Type: typ.typeExpr,
}
obj.Decl = typeSpec
gen.Specs = append(gen.Specs, typeSpec)
}
p.generated.Decls = append(p.generated.Decls, gen)
}
// findMissingCGoNames traverses the AST and finds all C.something names. Only
// these symbols are extracted from the parsed C AST and converted to the Go
// equivalent.
func (p *cgoPackage) findMissingCGoNames(cursor *astutil.Cursor) bool {
switch node := cursor.Node().(type) {
case *ast.SelectorExpr:
x, ok := node.X.(*ast.Ident)
if !ok {
return true
}
if x.Name == "C" {
name := node.Sel.Name
if _, ok := builtinAliases[name]; ok {
name = "_Cgo_" + name
}
p.missingSymbols[name] = struct{}{}
}
}
return true
}
// walker replaces all "C".<something> expressions to literal "C.<something>"
// expressions. Such expressions are impossible to write in Go (a dot cannot be
// used in the middle of a name) so in practice all C identifiers live in a
// separate namespace (no _Cgo_ hacks like in gc).
func (p *cgoPackage) walker(cursor *astutil.Cursor) bool {
switch node := cursor.Node().(type) {
case *ast.CallExpr:
fun, ok := node.Fun.(*ast.SelectorExpr)
if !ok {
return true
}
x, ok := fun.X.(*ast.Ident)
if !ok {
return true
}
if _, ok := p.functions[fun.Sel.Name]; ok && x.Name == "C" {
node.Fun = &ast.Ident{
NamePos: x.NamePos,
Name: "C." + fun.Sel.Name,
}
}
case *ast.SelectorExpr:
x, ok := node.X.(*ast.Ident)
if !ok {
return true
}
if x.Name == "C" {
name := "C." + node.Sel.Name
if _, ok := p.functions[node.Sel.Name]; ok {
name += "$funcaddr"
}
cursor.Replace(&ast.Ident{
NamePos: x.NamePos,
Name: name,
})
}
}
return true
}