main.go

Documentation: cmd/cgo

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Cgo; see doc.go for an overview.
     6  
     7  // TODO(rsc):
     8  //	Emit correct line number annotations.
     9  //	Make gc understand the annotations.
    10  
    11  package main
    12  
    13  import (
    14  	"flag"
    15  	"fmt"
    16  	"go/ast"
    17  	"go/printer"
    18  	"go/token"
    19  	"internal/buildcfg"
    20  	"io"
    21  	"os"
    22  	"path/filepath"
    23  	"reflect"
    24  	"runtime"
    25  	"sort"
    26  	"strings"
    27  
    28  	"cmd/internal/edit"
    29  	"cmd/internal/notsha256"
    30  	"cmd/internal/objabi"
    31  	"cmd/internal/telemetry/counter"
    32  )
    33  
    34  // A Package collects information about the package we're going to write.
    35  type Package struct {
    36  	PackageName string // name of package
    37  	PackagePath string
    38  	PtrSize     int64
    39  	IntSize     int64
    40  	GccOptions  []string
    41  	GccIsClang  bool
    42  	LdFlags     []string // #cgo LDFLAGS
    43  	Written     map[string]bool
    44  	Name        map[string]*Name // accumulated Name from Files
    45  	ExpFunc     []*ExpFunc       // accumulated ExpFunc from Files
    46  	Decl        []ast.Decl
    47  	GoFiles     []string        // list of Go files
    48  	GccFiles    []string        // list of gcc output files
    49  	Preamble    string          // collected preamble for _cgo_export.h
    50  	typedefs    map[string]bool // type names that appear in the types of the objects we're interested in
    51  	typedefList []typedefInfo
    52  	noCallbacks map[string]bool // C function names with #cgo nocallback directive
    53  	noEscapes   map[string]bool // C function names with #cgo noescape directive
    54  }
    55  
    56  // A typedefInfo is an element on Package.typedefList: a typedef name
    57  // and the position where it was required.
    58  type typedefInfo struct {
    59  	typedef string
    60  	pos     token.Pos
    61  }
    62  
    63  // A File collects information about a single Go input file.
    64  type File struct {
    65  	AST         *ast.File           // parsed AST
    66  	Comments    []*ast.CommentGroup // comments from file
    67  	Package     string              // Package name
    68  	Preamble    string              // C preamble (doc comment on import "C")
    69  	Ref         []*Ref              // all references to C.xxx in AST
    70  	Calls       []*Call             // all calls to C.xxx in AST
    71  	ExpFunc     []*ExpFunc          // exported functions for this file
    72  	Name        map[string]*Name    // map from Go name to Name
    73  	NamePos     map[*Name]token.Pos // map from Name to position of the first reference
    74  	NoCallbacks map[string]bool     // C function names that with #cgo nocallback directive
    75  	NoEscapes   map[string]bool     // C function names that with #cgo noescape directive
    76  	Edit        *edit.Buffer
    77  }
    78  
    79  func (f *File) offset(p token.Pos) int {
    80  	return fset.Position(p).Offset
    81  }
    82  
    83  func nameKeys(m map[string]*Name) []string {
    84  	var ks []string
    85  	for k := range m {
    86  		ks = append(ks, k)
    87  	}
    88  	sort.Strings(ks)
    89  	return ks
    90  }
    91  
    92  // A Call refers to a call of a C.xxx function in the AST.
    93  type Call struct {
    94  	Call     *ast.CallExpr
    95  	Deferred bool
    96  	Done     bool
    97  }
    98  
    99  // A Ref refers to an expression of the form C.xxx in the AST.
   100  type Ref struct {
   101  	Name    *Name
   102  	Expr    *ast.Expr
   103  	Context astContext
   104  	Done    bool
   105  }
   106  
   107  func (r *Ref) Pos() token.Pos {
   108  	return (*r.Expr).Pos()
   109  }
   110  
   111  var nameKinds = []string{"iconst", "fconst", "sconst", "type", "var", "fpvar", "func", "macro", "not-type"}
   112  
   113  // A Name collects information about C.xxx.
   114  type Name struct {
   115  	Go       string // name used in Go referring to package C
   116  	Mangle   string // name used in generated Go
   117  	C        string // name used in C
   118  	Define   string // #define expansion
   119  	Kind     string // one of the nameKinds
   120  	Type     *Type  // the type of xxx
   121  	FuncType *FuncType
   122  	AddError bool
   123  	Const    string // constant definition
   124  }
   125  
   126  // IsVar reports whether Kind is either "var" or "fpvar"
   127  func (n *Name) IsVar() bool {
   128  	return n.Kind == "var" || n.Kind == "fpvar"
   129  }
   130  
   131  // IsConst reports whether Kind is either "iconst", "fconst" or "sconst"
   132  func (n *Name) IsConst() bool {
   133  	return strings.HasSuffix(n.Kind, "const")
   134  }
   135  
   136  // An ExpFunc is an exported function, callable from C.
   137  // Such functions are identified in the Go input file
   138  // by doc comments containing the line //export ExpName
   139  type ExpFunc struct {
   140  	Func    *ast.FuncDecl
   141  	ExpName string // name to use from C
   142  	Doc     string
   143  }
   144  
   145  // A TypeRepr contains the string representation of a type.
   146  type TypeRepr struct {
   147  	Repr       string
   148  	FormatArgs []interface{}
   149  }
   150  
   151  // A Type collects information about a type in both the C and Go worlds.
   152  type Type struct {
   153  	Size       int64
   154  	Align      int64
   155  	C          *TypeRepr
   156  	Go         ast.Expr
   157  	EnumValues map[string]int64
   158  	Typedef    string
   159  	BadPointer bool // this pointer type should be represented as a uintptr (deprecated)
   160  }
   161  
   162  // A FuncType collects information about a function type in both the C and Go worlds.
   163  type FuncType struct {
   164  	Params []*Type
   165  	Result *Type
   166  	Go     *ast.FuncType
   167  }
   168  
   169  func usage() {
   170  	fmt.Fprint(os.Stderr, "usage: cgo -- [compiler options] file.go ...\n")
   171  	flag.PrintDefaults()
   172  	os.Exit(2)
   173  }
   174  
   175  var ptrSizeMap = map[string]int64{
   176  	"386":      4,
   177  	"alpha":    8,
   178  	"amd64":    8,
   179  	"arm":      4,
   180  	"arm64":    8,
   181  	"loong64":  8,
   182  	"m68k":     4,
   183  	"mips":     4,
   184  	"mipsle":   4,
   185  	"mips64":   8,
   186  	"mips64le": 8,
   187  	"nios2":    4,
   188  	"ppc":      4,
   189  	"ppc64":    8,
   190  	"ppc64le":  8,
   191  	"riscv":    4,
   192  	"riscv64":  8,
   193  	"s390":     4,
   194  	"s390x":    8,
   195  	"sh":       4,
   196  	"shbe":     4,
   197  	"sparc":    4,
   198  	"sparc64":  8,
   199  }
   200  
   201  var intSizeMap = map[string]int64{
   202  	"386":      4,
   203  	"alpha":    8,
   204  	"amd64":    8,
   205  	"arm":      4,
   206  	"arm64":    8,
   207  	"loong64":  8,
   208  	"m68k":     4,
   209  	"mips":     4,
   210  	"mipsle":   4,
   211  	"mips64":   8,
   212  	"mips64le": 8,
   213  	"nios2":    4,
   214  	"ppc":      4,
   215  	"ppc64":    8,
   216  	"ppc64le":  8,
   217  	"riscv":    4,
   218  	"riscv64":  8,
   219  	"s390":     4,
   220  	"s390x":    8,
   221  	"sh":       4,
   222  	"shbe":     4,
   223  	"sparc":    4,
   224  	"sparc64":  8,
   225  }
   226  
   227  var cPrefix string
   228  
   229  var fset = token.NewFileSet()
   230  
   231  var dynobj = flag.String("dynimport", "", "if non-empty, print dynamic import data for that file")
   232  var dynout = flag.String("dynout", "", "write -dynimport output to this file")
   233  var dynpackage = flag.String("dynpackage", "main", "set Go package for -dynimport output")
   234  var dynlinker = flag.Bool("dynlinker", false, "record dynamic linker information in -dynimport mode")
   235  
   236  // This flag is for bootstrapping a new Go implementation,
   237  // to generate Go types that match the data layout and
   238  // constant values used in the host's C libraries and system calls.
   239  var godefs = flag.Bool("godefs", false, "for bootstrap: write Go definitions for C file to standard output")
   240  
   241  var srcDir = flag.String("srcdir", "", "source directory")
   242  var objDir = flag.String("objdir", "", "object directory")
   243  var importPath = flag.String("importpath", "", "import path of package being built (for comments in generated files)")
   244  var exportHeader = flag.String("exportheader", "", "where to write export header if any exported functions")
   245  
   246  var ldflags = flag.String("ldflags", "", "flags to pass to C linker")
   247  
   248  var gccgo = flag.Bool("gccgo", false, "generate files for use with gccgo")
   249  var gccgoprefix = flag.String("gccgoprefix", "", "-fgo-prefix option used with gccgo")
   250  var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used with gccgo")
   251  var gccgoMangler func(string) string
   252  var gccgoDefineCgoIncomplete = flag.Bool("gccgo_define_cgoincomplete", false, "define cgo.Incomplete for older gccgo/GoLLVM")
   253  var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
   254  var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
   255  var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")
   256  
   257  var goarch, goos, gomips, gomips64 string
   258  var gccBaseCmd []string
   259  
   260  func main() {
   261  	counter.Open()
   262  	objabi.AddVersionFlag() // -V
   263  	objabi.Flagparse(usage)
   264  	counter.Inc("cgo/invocations")
   265  	counter.CountFlags("cgo/flag:", *flag.CommandLine)
   266  
   267  	if *gccgoDefineCgoIncomplete {
   268  		if !*gccgo {
   269  			fmt.Fprintf(os.Stderr, "cgo: -gccgo_define_cgoincomplete without -gccgo\n")
   270  			os.Exit(2)
   271  		}
   272  		incomplete = "_cgopackage_Incomplete"
   273  	}
   274  
   275  	if *dynobj != "" {
   276  		// cgo -dynimport is essentially a separate helper command
   277  		// built into the cgo binary. It scans a gcc-produced executable
   278  		// and dumps information about the imported symbols and the
   279  		// imported libraries. The 'go build' rules for cgo prepare an
   280  		// appropriate executable and then use its import information
   281  		// instead of needing to make the linkers duplicate all the
   282  		// specialized knowledge gcc has about where to look for imported
   283  		// symbols and which ones to use.
   284  		dynimport(*dynobj)
   285  		return
   286  	}
   287  
   288  	if *godefs {
   289  		// Generating definitions pulled from header files,
   290  		// to be checked into Go repositories.
   291  		// Line numbers are just noise.
   292  		conf.Mode &^= printer.SourcePos
   293  	}
   294  
   295  	args := flag.Args()
   296  	if len(args) < 1 {
   297  		usage()
   298  	}
   299  
   300  	// Find first arg that looks like a go file and assume everything before
   301  	// that are options to pass to gcc.
   302  	var i int
   303  	for i = len(args); i > 0; i-- {
   304  		if !strings.HasSuffix(args[i-1], ".go") {
   305  			break
   306  		}
   307  	}
   308  	if i == len(args) {
   309  		usage()
   310  	}
   311  
   312  	// Save original command line arguments for the godefs generated comment. Relative file
   313  	// paths in os.Args will be rewritten to absolute file paths in the loop below.
   314  	osArgs := make([]string, len(os.Args))
   315  	copy(osArgs, os.Args[:])
   316  	goFiles := args[i:]
   317  
   318  	for _, arg := range args[:i] {
   319  		if arg == "-fsanitize=thread" {
   320  			tsanProlog = yesTsanProlog
   321  		}
   322  		if arg == "-fsanitize=memory" {
   323  			msanProlog = yesMsanProlog
   324  		}
   325  	}
   326  
   327  	p := newPackage(args[:i])
   328  
   329  	// We need a C compiler to be available. Check this.
   330  	var err error
   331  	gccBaseCmd, err = checkGCCBaseCmd()
   332  	if err != nil {
   333  		fatalf("%v", err)
   334  		os.Exit(2)
   335  	}
   336  
   337  	// Record linker flags for external linking.
   338  	if *ldflags != "" {
   339  		args, err := splitQuoted(*ldflags)
   340  		if err != nil {
   341  			fatalf("bad -ldflags option: %q (%s)", *ldflags, err)
   342  		}
   343  		p.addToFlag("LDFLAGS", args)
   344  	}
   345  
   346  	// For backward compatibility for Bazel, record CGO_LDFLAGS
   347  	// from the environment for external linking.
   348  	// This should not happen with cmd/go, which removes CGO_LDFLAGS
   349  	// from the environment when invoking cgo.
   350  	// This can be removed when we no longer need to support
   351  	// older versions of Bazel. See issue #66456 and
   352  	// https://github.com/bazelbuild/rules_go/issues/3979.
   353  	if envFlags := os.Getenv("CGO_LDFLAGS"); envFlags != "" {
   354  		args, err := splitQuoted(envFlags)
   355  		if err != nil {
   356  			fatalf("bad CGO_LDFLAGS: %q (%s)", envFlags, err)
   357  		}
   358  		p.addToFlag("LDFLAGS", args)
   359  	}
   360  
   361  	// Need a unique prefix for the global C symbols that
   362  	// we use to coordinate between gcc and ourselves.
   363  	// We already put _cgo_ at the beginning, so the main
   364  	// concern is other cgo wrappers for the same functions.
   365  	// Use the beginning of the notsha256 of the input to disambiguate.
   366  	h := notsha256.New()
   367  	io.WriteString(h, *importPath)
   368  	fs := make([]*File, len(goFiles))
   369  	for i, input := range goFiles {
   370  		if *srcDir != "" {
   371  			input = filepath.Join(*srcDir, input)
   372  		}
   373  
   374  		// Create absolute path for file, so that it will be used in error
   375  		// messages and recorded in debug line number information.
   376  		// This matches the rest of the toolchain. See golang.org/issue/5122.
   377  		if aname, err := filepath.Abs(input); err == nil {
   378  			input = aname
   379  		}
   380  
   381  		b, err := os.ReadFile(input)
   382  		if err != nil {
   383  			fatalf("%s", err)
   384  		}
   385  		if _, err = h.Write(b); err != nil {
   386  			fatalf("%s", err)
   387  		}
   388  
   389  		// Apply trimpath to the file path. The path won't be read from after this point.
   390  		input, _ = objabi.ApplyRewrites(input, *trimpath)
   391  		if strings.ContainsAny(input, "\r\n") {
   392  			// ParseGo, (*Package).writeOutput, and printer.Fprint in SourcePos mode
   393  			// all emit line directives, which don't permit newlines in the file path.
   394  			// Bail early if we see anything newline-like in the trimmed path.
   395  			fatalf("input path contains newline character: %q", input)
   396  		}
   397  		goFiles[i] = input
   398  
   399  		f := new(File)
   400  		f.Edit = edit.NewBuffer(b)
   401  		f.ParseGo(input, b)
   402  		f.ProcessCgoDirectives()
   403  		fs[i] = f
   404  	}
   405  
   406  	cPrefix = fmt.Sprintf("_%x", h.Sum(nil)[0:6])
   407  
   408  	if *objDir == "" {
   409  		*objDir = "_obj"
   410  	}
   411  	// make sure that `objDir` directory exists, so that we can write
   412  	// all the output files there.
   413  	os.MkdirAll(*objDir, 0o700)
   414  	*objDir += string(filepath.Separator)
   415  
   416  	for i, input := range goFiles {
   417  		f := fs[i]
   418  		p.Translate(f)
   419  		for _, cref := range f.Ref {
   420  			switch cref.Context {
   421  			case ctxCall, ctxCall2:
   422  				if cref.Name.Kind != "type" {
   423  					break
   424  				}
   425  				old := *cref.Expr
   426  				*cref.Expr = cref.Name.Type.Go
   427  				f.Edit.Replace(f.offset(old.Pos()), f.offset(old.End()), gofmt(cref.Name.Type.Go))
   428  			}
   429  		}
   430  		if nerrors > 0 {
   431  			os.Exit(2)
   432  		}
   433  		p.PackagePath = f.Package
   434  		p.Record(f)
   435  		if *godefs {
   436  			os.Stdout.WriteString(p.godefs(f, osArgs))
   437  		} else {
   438  			p.writeOutput(f, input)
   439  		}
   440  	}
   441  	cFunctions := make(map[string]bool)
   442  	for _, key := range nameKeys(p.Name) {
   443  		n := p.Name[key]
   444  		if n.FuncType != nil {
   445  			cFunctions[n.C] = true
   446  		}
   447  	}
   448  
   449  	for funcName := range p.noEscapes {
   450  		if _, found := cFunctions[funcName]; !found {
   451  			error_(token.NoPos, "#cgo noescape %s: no matched C function", funcName)
   452  		}
   453  	}
   454  
   455  	for funcName := range p.noCallbacks {
   456  		if _, found := cFunctions[funcName]; !found {
   457  			error_(token.NoPos, "#cgo nocallback %s: no matched C function", funcName)
   458  		}
   459  	}
   460  
   461  	if !*godefs {
   462  		p.writeDefs()
   463  	}
   464  	if nerrors > 0 {
   465  		os.Exit(2)
   466  	}
   467  }
   468  
   469  // newPackage returns a new Package that will invoke
   470  // gcc with the additional arguments specified in args.
   471  func newPackage(args []string) *Package {
   472  	goarch = runtime.GOARCH
   473  	if s := os.Getenv("GOARCH"); s != "" {
   474  		goarch = s
   475  	}
   476  	goos = runtime.GOOS
   477  	if s := os.Getenv("GOOS"); s != "" {
   478  		goos = s
   479  	}
   480  	buildcfg.Check()
   481  	gomips = buildcfg.GOMIPS
   482  	gomips64 = buildcfg.GOMIPS64
   483  	ptrSize := ptrSizeMap[goarch]
   484  	if ptrSize == 0 {
   485  		fatalf("unknown ptrSize for $GOARCH %q", goarch)
   486  	}
   487  	intSize := intSizeMap[goarch]
   488  	if intSize == 0 {
   489  		fatalf("unknown intSize for $GOARCH %q", goarch)
   490  	}
   491  
   492  	// Reset locale variables so gcc emits English errors [sic].
   493  	os.Setenv("LANG", "en_US.UTF-8")
   494  	os.Setenv("LC_ALL", "C")
   495  
   496  	p := &Package{
   497  		PtrSize:     ptrSize,
   498  		IntSize:     intSize,
   499  		Written:     make(map[string]bool),
   500  		noCallbacks: make(map[string]bool),
   501  		noEscapes:   make(map[string]bool),
   502  	}
   503  	p.addToFlag("CFLAGS", args)
   504  	return p
   505  }
   506  
   507  // Record what needs to be recorded about f.
   508  func (p *Package) Record(f *File) {
   509  	if p.PackageName == "" {
   510  		p.PackageName = f.Package
   511  	} else if p.PackageName != f.Package {
   512  		error_(token.NoPos, "inconsistent package names: %s, %s", p.PackageName, f.Package)
   513  	}
   514  
   515  	if p.Name == nil {
   516  		p.Name = f.Name
   517  	} else {
   518  		for k, v := range f.Name {
   519  			if p.Name[k] == nil {
   520  				p.Name[k] = v
   521  			} else if p.incompleteTypedef(p.Name[k].Type) {
   522  				p.Name[k] = v
   523  			} else if p.incompleteTypedef(v.Type) {
   524  				// Nothing to do.
   525  			} else if _, ok := nameToC[k]; ok {
   526  				// Names we predefine may appear inconsistent
   527  				// if some files typedef them and some don't.
   528  				// Issue 26743.
   529  			} else if !reflect.DeepEqual(p.Name[k], v) {
   530  				error_(token.NoPos, "inconsistent definitions for C.%s", fixGo(k))
   531  			}
   532  		}
   533  	}
   534  
   535  	// merge nocallback & noescape
   536  	for k, v := range f.NoCallbacks {
   537  		p.noCallbacks[k] = v
   538  	}
   539  	for k, v := range f.NoEscapes {
   540  		p.noEscapes[k] = v
   541  	}
   542  
   543  	if f.ExpFunc != nil {
   544  		p.ExpFunc = append(p.ExpFunc, f.ExpFunc...)
   545  		p.Preamble += "\n" + f.Preamble
   546  	}
   547  	p.Decl = append(p.Decl, f.AST.Decls...)
   548  }
   549  
   550  // incompleteTypedef reports whether t appears to be an incomplete
   551  // typedef definition.
   552  func (p *Package) incompleteTypedef(t *Type) bool {
   553  	return t == nil || (t.Size == 0 && t.Align == -1)
   554  }
   555
View as plain text