main.go

     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  	"maps"
    22  	"os"
    23  	"path/filepath"
    24  	"reflect"
    25  	"runtime"
    26  	"sort"
    27  	"strings"
    28  	"sync"
    29  
    30  	"cmd/internal/edit"
    31  	"cmd/internal/hash"
    32  	"cmd/internal/objabi"
    33  	"cmd/internal/telemetry/counter"
    34  )
    35  
    36  // A Package collects information about the package we're going to write.
    37  type Package struct {
    38  	PackageName string // name of package
    39  	PackagePath string
    40  	PtrSize     int64
    41  	IntSize     int64
    42  	GccOptions  []string
    43  	GccIsClang  bool
    44  	LdFlags     []string // #cgo LDFLAGS
    45  	Written     map[string]bool
    46  	Name        map[string]*Name // accumulated Name from Files
    47  	ExpFunc     []*ExpFunc       // accumulated ExpFunc from Files
    48  	Decl        []ast.Decl
    49  	GoFiles     []string        // list of Go files
    50  	GccFiles    []string        // list of gcc output files
    51  	Preamble    string          // collected preamble for _cgo_export.h
    52  	typedefs    map[string]bool // type names that appear in the types of the objects we're interested in
    53  	typedefList []typedefInfo
    54  	noCallbacks map[string]bool // C function names with #cgo nocallback directive
    55  	noEscapes   map[string]bool // C function names with #cgo noescape directive
    56  }
    57  
    58  // A typedefInfo is an element on Package.typedefList: a typedef name
    59  // and the position where it was required.
    60  type typedefInfo struct {
    61  	typedef string
    62  	pos     token.Pos
    63  }
    64  
    65  // A File collects information about a single Go input file.
    66  type File struct {
    67  	AST         *ast.File           // parsed AST
    68  	Comments    []*ast.CommentGroup // comments from file
    69  	Package     string              // Package name
    70  	Preamble    string              // C preamble (doc comment on import "C")
    71  	Ref         []*Ref              // all references to C.xxx in AST
    72  	Calls       []*Call             // all calls to C.xxx in AST
    73  	ExpFunc     []*ExpFunc          // exported functions for this file
    74  	Name        map[string]*Name    // map from Go name to Name
    75  	NamePos     map[*Name]token.Pos // map from Name to position of the first reference
    76  	NoCallbacks map[string]bool     // C function names that with #cgo nocallback directive
    77  	NoEscapes   map[string]bool     // C function names that with #cgo noescape directive
    78  	Edit        *edit.Buffer
    79  }
    80  
    81  func (f *File) offset(p token.Pos) int {
    82  	return fset.Position(p).Offset
    83  }
    84  
    85  func nameKeys(m map[string]*Name) []string {
    86  	ks := make([]string, 0, len(m))
    87  	for k := range m {
    88  		ks = append(ks, k)
    89  	}
    90  	sort.Strings(ks)
    91  	return ks
    92  }
    93  
    94  // A Call refers to a call of a C.xxx function in the AST.
    95  type Call struct {
    96  	Call     *ast.CallExpr
    97  	Deferred bool
    98  	Done     bool
    99  }
   100  
   101  // A Ref refers to an expression of the form C.xxx in the AST.
   102  type Ref struct {
   103  	Name    *Name
   104  	Expr    *ast.Expr
   105  	Context astContext
   106  	Done    bool
   107  }
   108  
   109  func (r *Ref) Pos() token.Pos {
   110  	return (*r.Expr).Pos()
   111  }
   112  
   113  var nameKinds = []string{"iconst", "fconst", "sconst", "type", "var", "fpvar", "func", "macro", "not-type"}
   114  
   115  // A Name collects information about C.xxx.
   116  type Name struct {
   117  	Go       string // name used in Go referring to package C
   118  	Mangle   string // name used in generated Go
   119  	C        string // name used in C
   120  	Define   string // #define expansion
   121  	Kind     string // one of the nameKinds
   122  	Type     *Type  // the type of xxx
   123  	FuncType *FuncType
   124  	AddError bool
   125  	Const    string // constant definition
   126  }
   127  
   128  // IsVar reports whether Kind is either "var" or "fpvar"
   129  func (n *Name) IsVar() bool {
   130  	return n.Kind == "var" || n.Kind == "fpvar"
   131  }
   132  
   133  // IsConst reports whether Kind is either "iconst", "fconst" or "sconst"
   134  func (n *Name) IsConst() bool {
   135  	return strings.HasSuffix(n.Kind, "const")
   136  }
   137  
   138  // An ExpFunc is an exported function, callable from C.
   139  // Such functions are identified in the Go input file
   140  // by doc comments containing the line //export ExpName
   141  type ExpFunc struct {
   142  	Func    *ast.FuncDecl
   143  	ExpName string // name to use from C
   144  	Doc     string
   145  }
   146  
   147  // A TypeRepr contains the string representation of a type.
   148  type TypeRepr struct {
   149  	Repr       string
   150  	FormatArgs []interface{}
   151  }
   152  
   153  // A Type collects information about a type in both the C and Go worlds.
   154  type Type struct {
   155  	Size       int64
   156  	Align      int64
   157  	C          *TypeRepr
   158  	Go         ast.Expr
   159  	EnumValues map[string]int64
   160  	Typedef    string
   161  	BadPointer bool // this pointer type should be represented as a uintptr (deprecated)
   162  }
   163  
   164  func (t *Type) fuzzyMatch(t2 *Type) bool {
   165  	if t == nil || t2 == nil {
   166  		return false
   167  	}
   168  	return t.Size == t2.Size && t.Align == t2.Align
   169  }
   170  
   171  // A FuncType collects information about a function type in both the C and Go worlds.
   172  type FuncType struct {
   173  	Params []*Type
   174  	Result *Type
   175  	Go     *ast.FuncType
   176  }
   177  
   178  func (t *FuncType) fuzzyMatch(t2 *FuncType) bool {
   179  	if t == nil || t2 == nil {
   180  		return false
   181  	}
   182  	if !t.Result.fuzzyMatch(t2.Result) {
   183  		return false
   184  	}
   185  	if len(t.Params) != len(t2.Params) {
   186  		return false
   187  	}
   188  	for i := range t.Params {
   189  		if !t.Params[i].fuzzyMatch(t2.Params[i]) {
   190  			return false
   191  		}
   192  	}
   193  	return true
   194  }
   195  
   196  func usage() {
   197  	fmt.Fprint(os.Stderr, "usage: cgo -- [compiler options] file.go ...\n")
   198  	flag.PrintDefaults()
   199  	os.Exit(2)
   200  }
   201  
   202  var ptrSizeMap = map[string]int64{
   203  	"386":      4,
   204  	"alpha":    8,
   205  	"amd64":    8,
   206  	"arm":      4,
   207  	"arm64":    8,
   208  	"loong64":  8,
   209  	"m68k":     4,
   210  	"mips":     4,
   211  	"mipsle":   4,
   212  	"mips64":   8,
   213  	"mips64le": 8,
   214  	"nios2":    4,
   215  	"ppc":      4,
   216  	"ppc64":    8,
   217  	"ppc64le":  8,
   218  	"riscv":    4,
   219  	"riscv64":  8,
   220  	"s390":     4,
   221  	"s390x":    8,
   222  	"sh":       4,
   223  	"shbe":     4,
   224  	"sparc":    4,
   225  	"sparc64":  8,
   226  }
   227  
   228  var intSizeMap = map[string]int64{
   229  	"386":      4,
   230  	"alpha":    8,
   231  	"amd64":    8,
   232  	"arm":      4,
   233  	"arm64":    8,
   234  	"loong64":  8,
   235  	"m68k":     4,
   236  	"mips":     4,
   237  	"mipsle":   4,
   238  	"mips64":   8,
   239  	"mips64le": 8,
   240  	"nios2":    4,
   241  	"ppc":      4,
   242  	"ppc64":    8,
   243  	"ppc64le":  8,
   244  	"riscv":    4,
   245  	"riscv64":  8,
   246  	"s390":     4,
   247  	"s390x":    8,
   248  	"sh":       4,
   249  	"shbe":     4,
   250  	"sparc":    4,
   251  	"sparc64":  8,
   252  }
   253  
   254  var cPrefix string
   255  
   256  var fset = token.NewFileSet()
   257  
   258  var dynobj = flag.String("dynimport", "", "if non-empty, print dynamic import data for that file")
   259  var dynout = flag.String("dynout", "", "write -dynimport output to this file")
   260  var dynpackage = flag.String("dynpackage", "main", "set Go package for -dynimport output")
   261  var dynlinker = flag.Bool("dynlinker", false, "record dynamic linker information in -dynimport mode")
   262  
   263  // This flag is for bootstrapping a new Go implementation,
   264  // to generate Go types that match the data layout and
   265  // constant values used in the host's C libraries and system calls.
   266  var godefs = flag.Bool("godefs", false, "for bootstrap: write Go definitions for C file to standard output")
   267  
   268  var srcDir = flag.String("srcdir", "", "source directory")
   269  var objDir = flag.String("objdir", "", "object directory")
   270  var importPath = flag.String("importpath", "", "import path of package being built (for comments in generated files)")
   271  var exportHeader = flag.String("exportheader", "", "where to write export header if any exported functions")
   272  
   273  var ldflags = flag.String("ldflags", "", "flags to pass to C linker")
   274  
   275  var gccgo = flag.Bool("gccgo", false, "generate files for use with gccgo")
   276  var gccgoprefix = flag.String("gccgoprefix", "", "-fgo-prefix option used with gccgo")
   277  var gccgopkgpath = flag.String("gccgopkgpath", "", "-fgo-pkgpath option used with gccgo")
   278  var gccgoMangler func(string) string
   279  var gccgoDefineCgoIncomplete = flag.Bool("gccgo_define_cgoincomplete", false, "define cgo.Incomplete for older gccgo/GoLLVM")
   280  var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
   281  var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
   282  var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")
   283  
   284  var goarch, goos, gomips, gomips64 string
   285  var gccBaseCmd []string
   286  
   287  func main() {
   288  	counter.Open()
   289  	objabi.AddVersionFlag() // -V
   290  	objabi.Flagparse(usage)
   291  	counter.Inc("cgo/invocations")
   292  	counter.CountFlags("cgo/flag:", *flag.CommandLine)
   293  
   294  	if *gccgoDefineCgoIncomplete {
   295  		if !*gccgo {
   296  			fmt.Fprintf(os.Stderr, "cgo: -gccgo_define_cgoincomplete without -gccgo\n")
   297  			os.Exit(2)
   298  		}
   299  		incomplete = "_cgopackage_Incomplete"
   300  	}
   301  
   302  	if *dynobj != "" {
   303  		// cgo -dynimport is essentially a separate helper command
   304  		// built into the cgo binary. It scans a gcc-produced executable
   305  		// and dumps information about the imported symbols and the
   306  		// imported libraries. The 'go build' rules for cgo prepare an
   307  		// appropriate executable and then use its import information
   308  		// instead of needing to make the linkers duplicate all the
   309  		// specialized knowledge gcc has about where to look for imported
   310  		// symbols and which ones to use.
   311  		dynimport(*dynobj)
   312  		return
   313  	}
   314  
   315  	if *godefs {
   316  		// Generating definitions pulled from header files,
   317  		// to be checked into Go repositories.
   318  		// Line numbers are just noise.
   319  		conf.Mode &^= printer.SourcePos
   320  	}
   321  
   322  	args := flag.Args()
   323  	if len(args) < 1 {
   324  		usage()
   325  	}
   326  
   327  	// Find first arg that looks like a go file and assume everything before
   328  	// that are options to pass to gcc.
   329  	var i int
   330  	for i = len(args); i > 0; i-- {
   331  		if !strings.HasSuffix(args[i-1], ".go") {
   332  			break
   333  		}
   334  	}
   335  	if i == len(args) {
   336  		usage()
   337  	}
   338  
   339  	// Save original command line arguments for the godefs generated comment. Relative file
   340  	// paths in os.Args will be rewritten to absolute file paths in the loop below.
   341  	osArgs := make([]string, len(os.Args))
   342  	copy(osArgs, os.Args[:])
   343  	goFiles := args[i:]
   344  
   345  	for _, arg := range args[:i] {
   346  		if arg == "-fsanitize=thread" {
   347  			tsanProlog = yesTsanProlog
   348  		}
   349  		if arg == "-fsanitize=memory" {
   350  			msanProlog = yesMsanProlog
   351  		}
   352  	}
   353  
   354  	p := newPackage(args[:i])
   355  
   356  	// We need a C compiler to be available. Check this.
   357  	var err error
   358  	gccBaseCmd, err = checkGCCBaseCmd()
   359  	if err != nil {
   360  		fatalf("%v", err)
   361  		os.Exit(2)
   362  	}
   363  
   364  	// Record linker flags for external linking.
   365  	if *ldflags != "" {
   366  		args, err := splitQuoted(*ldflags)
   367  		if err != nil {
   368  			fatalf("bad -ldflags option: %q (%s)", *ldflags, err)
   369  		}
   370  		p.addToFlag("LDFLAGS", args)
   371  	}
   372  
   373  	// For backward compatibility for Bazel, record CGO_LDFLAGS
   374  	// from the environment for external linking.
   375  	// This should not happen with cmd/go, which removes CGO_LDFLAGS
   376  	// from the environment when invoking cgo.
   377  	// This can be removed when we no longer need to support
   378  	// older versions of Bazel. See issue #66456 and
   379  	// https://github.com/bazelbuild/rules_go/issues/3979.
   380  	if envFlags := os.Getenv("CGO_LDFLAGS"); envFlags != "" {
   381  		args, err := splitQuoted(envFlags)
   382  		if err != nil {
   383  			fatalf("bad CGO_LDFLAGS: %q (%s)", envFlags, err)
   384  		}
   385  		p.addToFlag("LDFLAGS", args)
   386  	}
   387  
   388  	// Need a unique prefix for the global C symbols that
   389  	// we use to coordinate between gcc and ourselves.
   390  	// We already put _cgo_ at the beginning, so the main
   391  	// concern is other cgo wrappers for the same functions.
   392  	// Use the beginning of the 16 bytes hash of the input to disambiguate.
   393  	h := hash.New16()
   394  	io.WriteString(h, *importPath)
   395  	var once sync.Once
   396  	var wg sync.WaitGroup
   397  	fs := make([]*File, len(goFiles))
   398  	for i, input := range goFiles {
   399  		if *srcDir != "" {
   400  			input = filepath.Join(*srcDir, input)
   401  		}
   402  
   403  		// Create absolute path for file, so that it will be used in error
   404  		// messages and recorded in debug line number information.
   405  		// This matches the rest of the toolchain. See golang.org/issue/5122.
   406  		if aname, err := filepath.Abs(input); err == nil {
   407  			input = aname
   408  		}
   409  
   410  		b, err := os.ReadFile(input)
   411  		if err != nil {
   412  			fatalf("%s", err)
   413  		}
   414  		if _, err = h.Write(b); err != nil {
   415  			fatalf("%s", err)
   416  		}
   417  
   418  		wg.Add(1)
   419  		go func() {
   420  			defer wg.Done()
   421  			// Apply trimpath to the file path. The path won't be read from after this point.
   422  			input, _ = objabi.ApplyRewrites(input, *trimpath)
   423  			if strings.ContainsAny(input, "\r\n") {
   424  				// ParseGo, (*Package).writeOutput, and printer.Fprint in SourcePos mode
   425  				// all emit line directives, which don't permit newlines in the file path.
   426  				// Bail early if we see anything newline-like in the trimmed path.
   427  				fatalf("input path contains newline character: %q", input)
   428  			}
   429  			goFiles[i] = input
   430  
   431  			f := new(File)
   432  			f.Edit = edit.NewBuffer(b)
   433  			f.ParseGo(input, b)
   434  			f.ProcessCgoDirectives()
   435  			gccIsClang := f.loadDefines(p.GccOptions)
   436  			once.Do(func() {
   437  				p.GccIsClang = gccIsClang
   438  			})
   439  
   440  			fs[i] = f
   441  		}()
   442  	}
   443  
   444  	wg.Wait()
   445  
   446  	cPrefix = fmt.Sprintf("_%x", h.Sum(nil)[0:6])
   447  
   448  	if *objDir == "" {
   449  		*objDir = "_obj"
   450  	}
   451  	// make sure that `objDir` directory exists, so that we can write
   452  	// all the output files there.
   453  	os.MkdirAll(*objDir, 0o700)
   454  	*objDir += string(filepath.Separator)
   455  
   456  	for i, input := range goFiles {
   457  		f := fs[i]
   458  		p.Translate(f)
   459  		for _, cref := range f.Ref {
   460  			switch cref.Context {
   461  			case ctxCall, ctxCall2:
   462  				if cref.Name.Kind != "type" {
   463  					break
   464  				}
   465  				old := *cref.Expr
   466  				*cref.Expr = cref.Name.Type.Go
   467  				f.Edit.Replace(f.offset(old.Pos()), f.offset(old.End()), gofmt(cref.Name.Type.Go))
   468  			}
   469  		}
   470  		if nerrors > 0 {
   471  			os.Exit(2)
   472  		}
   473  		p.PackagePath = f.Package
   474  		p.Record(f)
   475  		if *godefs {
   476  			os.Stdout.WriteString(p.godefs(f, osArgs))
   477  		} else {
   478  			p.writeOutput(f, input)
   479  		}
   480  	}
   481  	cFunctions := make(map[string]bool)
   482  	for _, key := range nameKeys(p.Name) {
   483  		n := p.Name[key]
   484  		if n.FuncType != nil {
   485  			cFunctions[n.C] = true
   486  		}
   487  	}
   488  
   489  	for funcName := range p.noEscapes {
   490  		if _, found := cFunctions[funcName]; !found {
   491  			error_(token.NoPos, "#cgo noescape %s: no matched C function", funcName)
   492  		}
   493  	}
   494  
   495  	for funcName := range p.noCallbacks {
   496  		if _, found := cFunctions[funcName]; !found {
   497  			error_(token.NoPos, "#cgo nocallback %s: no matched C function", funcName)
   498  		}
   499  	}
   500  
   501  	if !*godefs {
   502  		p.writeDefs()
   503  	}
   504  	if nerrors > 0 {
   505  		os.Exit(2)
   506  	}
   507  }
   508  
   509  // newPackage returns a new Package that will invoke
   510  // gcc with the additional arguments specified in args.
   511  func newPackage(args []string) *Package {
   512  	goarch = runtime.GOARCH
   513  	if s := os.Getenv("GOARCH"); s != "" {
   514  		goarch = s
   515  	}
   516  	goos = runtime.GOOS
   517  	if s := os.Getenv("GOOS"); s != "" {
   518  		goos = s
   519  	}
   520  	buildcfg.Check()
   521  	gomips = buildcfg.GOMIPS
   522  	gomips64 = buildcfg.GOMIPS64
   523  	ptrSize := ptrSizeMap[goarch]
   524  	if ptrSize == 0 {
   525  		fatalf("unknown ptrSize for $GOARCH %q", goarch)
   526  	}
   527  	intSize := intSizeMap[goarch]
   528  	if intSize == 0 {
   529  		fatalf("unknown intSize for $GOARCH %q", goarch)
   530  	}
   531  
   532  	// Reset locale variables so gcc emits English errors [sic].
   533  	os.Setenv("LANG", "en_US.UTF-8")
   534  	os.Setenv("LC_ALL", "C")
   535  
   536  	p := &Package{
   537  		PtrSize:     ptrSize,
   538  		IntSize:     intSize,
   539  		Written:     make(map[string]bool),
   540  		noCallbacks: make(map[string]bool),
   541  		noEscapes:   make(map[string]bool),
   542  	}
   543  	p.addToFlag("CFLAGS", args)
   544  	return p
   545  }
   546  
   547  // Record what needs to be recorded about f.
   548  func (p *Package) Record(f *File) {
   549  	if p.PackageName == "" {
   550  		p.PackageName = f.Package
   551  	} else if p.PackageName != f.Package {
   552  		error_(token.NoPos, "inconsistent package names: %s, %s", p.PackageName, f.Package)
   553  	}
   554  
   555  	if p.Name == nil {
   556  		p.Name = f.Name
   557  	} else {
   558  		// Merge the new file's names in with the existing names.
   559  		for k, v := range f.Name {
   560  			if p.Name[k] == nil {
   561  				// Never seen before, just save it.
   562  				p.Name[k] = v
   563  			} else if p.incompleteTypedef(p.Name[k].Type) && p.Name[k].FuncType == nil {
   564  				// Old one is incomplete, just use new one.
   565  				p.Name[k] = v
   566  			} else if p.incompleteTypedef(v.Type) && v.FuncType == nil {
   567  				// New one is incomplete, just use old one.
   568  				// Nothing to do.
   569  			} else if _, ok := nameToC[k]; ok {
   570  				// Names we predefine may appear inconsistent
   571  				// if some files typedef them and some don't.
   572  				// Issue 26743.
   573  			} else if !reflect.DeepEqual(p.Name[k], v) {
   574  				// We don't require strict func type equality, because some functions
   575  				// can have things like typedef'd arguments that are equivalent to
   576  				// the standard arguments. e.g.
   577  				//     int usleep(unsigned);
   578  				//     int usleep(useconds_t);
   579  				// So we just check size/alignment of arguments. At least that
   580  				// avoids problems like those in #67670 and #67699.
   581  				ok := false
   582  				ft1 := p.Name[k].FuncType
   583  				ft2 := v.FuncType
   584  				if ft1.fuzzyMatch(ft2) {
   585  					// Retry DeepEqual with the FuncType field cleared.
   586  					x1 := *p.Name[k]
   587  					x2 := *v
   588  					x1.FuncType = nil
   589  					x2.FuncType = nil
   590  					if reflect.DeepEqual(&x1, &x2) {
   591  						ok = true
   592  					}
   593  				}
   594  				if !ok {
   595  					error_(token.NoPos, "inconsistent definitions for C.%s", fixGo(k))
   596  				}
   597  			}
   598  		}
   599  	}
   600  
   601  	// merge nocallback & noescape
   602  	maps.Copy(p.noCallbacks, f.NoCallbacks)
   603  	maps.Copy(p.noEscapes, f.NoEscapes)
   604  
   605  	if f.ExpFunc != nil {
   606  		p.ExpFunc = append(p.ExpFunc, f.ExpFunc...)
   607  		p.Preamble += "\n" + f.Preamble
   608  	}
   609  	p.Decl = append(p.Decl, f.AST.Decls...)
   610  }
   611  
   612  // incompleteTypedef reports whether t appears to be an incomplete
   613  // typedef definition.
   614  func (p *Package) incompleteTypedef(t *Type) bool {
   615  	return t == nil || (t.Size == 0 && t.Align == -1)
   616  }
   617
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