Source file src/cmd/cgo/out.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  package main
     6  
     7  import (
     8  	"bytes"
     9  	"cmd/internal/pkgpath"
    10  	"debug/elf"
    11  	"debug/macho"
    12  	"debug/pe"
    13  	"fmt"
    14  	"go/ast"
    15  	"go/printer"
    16  	"go/token"
    17  	"internal/xcoff"
    18  	"io"
    19  	"os"
    20  	"os/exec"
    21  	"path/filepath"
    22  	"regexp"
    23  	"sort"
    24  	"strings"
    25  	"unicode"
    26  )
    27  
    28  var (
    29  	conf         = printer.Config{Mode: printer.SourcePos, Tabwidth: 8}
    30  	noSourceConf = printer.Config{Tabwidth: 8}
    31  )
    32  
    33  // writeDefs creates output files to be compiled by gc and gcc.
    34  func (p *Package) writeDefs() {
    35  	var fgo2, fc io.Writer
    36  	f := creat(*objDir + "_cgo_gotypes.go")
    37  	defer f.Close()
    38  	fgo2 = f
    39  	if *gccgo {
    40  		f := creat(*objDir + "_cgo_defun.c")
    41  		defer f.Close()
    42  		fc = f
    43  	}
    44  	fm := creat(*objDir + "_cgo_main.c")
    45  
    46  	var gccgoInit strings.Builder
    47  
    48  	if !*gccgo {
    49  		for _, arg := range p.LdFlags {
    50  			fmt.Fprintf(fgo2, "//go:cgo_ldflag %q\n", arg)
    51  		}
    52  	} else {
    53  		fflg := creat(*objDir + "_cgo_flags")
    54  		for _, arg := range p.LdFlags {
    55  			fmt.Fprintf(fflg, "_CGO_LDFLAGS=%s\n", arg)
    56  		}
    57  		fflg.Close()
    58  	}
    59  
    60  	// Write C main file for using gcc to resolve imports.
    61  	fmt.Fprintf(fm, "#include <stddef.h>\n") // For size_t below.
    62  	fmt.Fprintf(fm, "int main(int argc __attribute__((unused)), char **argv __attribute__((unused))) { return 0; }\n")
    63  	if *importRuntimeCgo {
    64  		fmt.Fprintf(fm, "void crosscall2(void(*fn)(void*) __attribute__((unused)), void *a __attribute__((unused)), int c __attribute__((unused)), size_t ctxt __attribute__((unused))) { }\n")
    65  		fmt.Fprintf(fm, "size_t _cgo_wait_runtime_init_done(void) { return 0; }\n")
    66  		fmt.Fprintf(fm, "void _cgo_release_context(size_t ctxt __attribute__((unused))) { }\n")
    67  		fmt.Fprintf(fm, "char* _cgo_topofstack(void) { return (char*)0; }\n")
    68  	} else {
    69  		// If we're not importing runtime/cgo, we *are* runtime/cgo,
    70  		// which provides these functions. We just need a prototype.
    71  		fmt.Fprintf(fm, "void crosscall2(void(*fn)(void*), void *a, int c, size_t ctxt);\n")
    72  		fmt.Fprintf(fm, "size_t _cgo_wait_runtime_init_done(void);\n")
    73  		fmt.Fprintf(fm, "void _cgo_release_context(size_t);\n")
    74  	}
    75  	fmt.Fprintf(fm, "void _cgo_allocate(void *a __attribute__((unused)), int c __attribute__((unused))) { }\n")
    76  	fmt.Fprintf(fm, "void _cgo_panic(void *a __attribute__((unused)), int c __attribute__((unused))) { }\n")
    77  	fmt.Fprintf(fm, "void _cgo_reginit(void) { }\n")
    78  
    79  	// Write second Go output: definitions of _C_xxx.
    80  	// In a separate file so that the import of "unsafe" does not
    81  	// pollute the original file.
    82  	fmt.Fprintf(fgo2, "// Code generated by cmd/cgo; DO NOT EDIT.\n\n")
    83  	fmt.Fprintf(fgo2, "package %s\n\n", p.PackageName)
    84  	fmt.Fprintf(fgo2, "import \"unsafe\"\n\n")
    85  	if *importSyscall {
    86  		fmt.Fprintf(fgo2, "import \"syscall\"\n\n")
    87  	}
    88  	if *importRuntimeCgo {
    89  		if !*gccgoDefineCgoIncomplete {
    90  			fmt.Fprintf(fgo2, "import _cgopackage \"runtime/cgo\"\n\n")
    91  			fmt.Fprintf(fgo2, "type _ _cgopackage.Incomplete\n") // prevent import-not-used error
    92  		} else {
    93  			fmt.Fprintf(fgo2, "//go:notinheap\n")
    94  			fmt.Fprintf(fgo2, "type _cgopackage_Incomplete struct{ _ struct{ _ struct{} } }\n")
    95  		}
    96  	}
    97  	if *importSyscall {
    98  		fmt.Fprintf(fgo2, "var _ syscall.Errno\n")
    99  	}
   100  	fmt.Fprintf(fgo2, "func _Cgo_ptr(ptr unsafe.Pointer) unsafe.Pointer { return ptr }\n\n")
   101  
   102  	if !*gccgo {
   103  		fmt.Fprintf(fgo2, "//go:linkname _Cgo_always_false runtime.cgoAlwaysFalse\n")
   104  		fmt.Fprintf(fgo2, "var _Cgo_always_false bool\n")
   105  		fmt.Fprintf(fgo2, "//go:linkname _Cgo_use runtime.cgoUse\n")
   106  		fmt.Fprintf(fgo2, "func _Cgo_use(interface{})\n")
   107  		fmt.Fprintf(fgo2, "//go:linkname _Cgo_keepalive runtime.cgoKeepAlive\n")
   108  		fmt.Fprintf(fgo2, "//go:noescape\n")
   109  		fmt.Fprintf(fgo2, "func _Cgo_keepalive(interface{})\n")
   110  	}
   111  	fmt.Fprintf(fgo2, "//go:linkname _Cgo_no_callback runtime.cgoNoCallback\n")
   112  	fmt.Fprintf(fgo2, "func _Cgo_no_callback(bool)\n")
   113  
   114  	typedefNames := make([]string, 0, len(typedef))
   115  	for name := range typedef {
   116  		if name == "_Ctype_void" {
   117  			// We provide an appropriate declaration for
   118  			// _Ctype_void below (#39877).
   119  			continue
   120  		}
   121  		typedefNames = append(typedefNames, name)
   122  	}
   123  	sort.Strings(typedefNames)
   124  	for _, name := range typedefNames {
   125  		def := typedef[name]
   126  		fmt.Fprintf(fgo2, "type %s ", name)
   127  		// We don't have source info for these types, so write them out without source info.
   128  		// Otherwise types would look like:
   129  		//
   130  		// type _Ctype_struct_cb struct {
   131  		// //line :1
   132  		//        on_test *[0]byte
   133  		// //line :1
   134  		// }
   135  		//
   136  		// Which is not useful. Moreover we never override source info,
   137  		// so subsequent source code uses the same source info.
   138  		// Moreover, empty file name makes compile emit no source debug info at all.
   139  		var buf bytes.Buffer
   140  		noSourceConf.Fprint(&buf, fset, def.Go)
   141  		if bytes.HasPrefix(buf.Bytes(), []byte("_Ctype_")) ||
   142  			strings.HasPrefix(name, "_Ctype_enum_") ||
   143  			strings.HasPrefix(name, "_Ctype_union_") {
   144  			// This typedef is of the form `typedef a b` and should be an alias.
   145  			fmt.Fprintf(fgo2, "= ")
   146  		}
   147  		fmt.Fprintf(fgo2, "%s", buf.Bytes())
   148  		fmt.Fprintf(fgo2, "\n\n")
   149  	}
   150  	if *gccgo {
   151  		fmt.Fprintf(fgo2, "type _Ctype_void byte\n")
   152  	} else {
   153  		fmt.Fprintf(fgo2, "type _Ctype_void [0]byte\n")
   154  	}
   155  
   156  	if *gccgo {
   157  		fmt.Fprint(fgo2, gccgoGoProlog)
   158  		fmt.Fprint(fc, p.cPrologGccgo())
   159  	} else {
   160  		fmt.Fprint(fgo2, goProlog)
   161  	}
   162  
   163  	if fc != nil {
   164  		fmt.Fprintf(fc, "#line 1 \"cgo-generated-wrappers\"\n")
   165  	}
   166  	if fm != nil {
   167  		fmt.Fprintf(fm, "#line 1 \"cgo-generated-wrappers\"\n")
   168  	}
   169  
   170  	gccgoSymbolPrefix := p.gccgoSymbolPrefix()
   171  
   172  	cVars := make(map[string]bool)
   173  	for _, key := range nameKeys(p.Name) {
   174  		n := p.Name[key]
   175  		if !n.IsVar() {
   176  			continue
   177  		}
   178  
   179  		if !cVars[n.C] {
   180  			if *gccgo {
   181  				fmt.Fprintf(fc, "extern byte *%s;\n", n.C)
   182  			} else {
   183  				// Force a reference to all symbols so that
   184  				// the external linker will add DT_NEEDED
   185  				// entries as needed on ELF systems.
   186  				// Treat function variables differently
   187  				// to avoid type conflict errors from LTO
   188  				// (Link Time Optimization).
   189  				if n.Kind == "fpvar" {
   190  					fmt.Fprintf(fm, "extern void %s();\n", n.C)
   191  				} else {
   192  					fmt.Fprintf(fm, "extern char %s[];\n", n.C)
   193  					fmt.Fprintf(fm, "void *_cgohack_%s = %s;\n\n", n.C, n.C)
   194  				}
   195  				fmt.Fprintf(fgo2, "//go:linkname __cgo_%s %s\n", n.C, n.C)
   196  				fmt.Fprintf(fgo2, "//go:cgo_import_static %s\n", n.C)
   197  				fmt.Fprintf(fgo2, "var __cgo_%s byte\n", n.C)
   198  			}
   199  			cVars[n.C] = true
   200  		}
   201  
   202  		var node ast.Node
   203  		if n.Kind == "var" {
   204  			node = &ast.StarExpr{X: n.Type.Go}
   205  		} else if n.Kind == "fpvar" {
   206  			node = n.Type.Go
   207  		} else {
   208  			panic(fmt.Errorf("invalid var kind %q", n.Kind))
   209  		}
   210  		if *gccgo {
   211  			fmt.Fprintf(fc, `extern void *%s __asm__("%s.%s");`, n.Mangle, gccgoSymbolPrefix, gccgoToSymbol(n.Mangle))
   212  			fmt.Fprintf(&gccgoInit, "\t%s = &%s;\n", n.Mangle, n.C)
   213  			fmt.Fprintf(fc, "\n")
   214  		}
   215  
   216  		fmt.Fprintf(fgo2, "var %s ", n.Mangle)
   217  		conf.Fprint(fgo2, fset, node)
   218  		if !*gccgo {
   219  			fmt.Fprintf(fgo2, " = (")
   220  			conf.Fprint(fgo2, fset, node)
   221  			fmt.Fprintf(fgo2, ")(unsafe.Pointer(&__cgo_%s))", n.C)
   222  		}
   223  		fmt.Fprintf(fgo2, "\n")
   224  	}
   225  	if *gccgo {
   226  		fmt.Fprintf(fc, "\n")
   227  	}
   228  
   229  	for _, key := range nameKeys(p.Name) {
   230  		n := p.Name[key]
   231  		if n.Const != "" {
   232  			fmt.Fprintf(fgo2, "const %s = %s\n", n.Mangle, n.Const)
   233  		}
   234  	}
   235  	fmt.Fprintf(fgo2, "\n")
   236  
   237  	callsMalloc := false
   238  	for _, key := range nameKeys(p.Name) {
   239  		n := p.Name[key]
   240  		if n.FuncType != nil {
   241  			p.writeDefsFunc(fgo2, n, &callsMalloc)
   242  		}
   243  	}
   244  
   245  	fgcc := creat(*objDir + "_cgo_export.c")
   246  	fgcch := creat(*objDir + "_cgo_export.h")
   247  	if *gccgo {
   248  		p.writeGccgoExports(fgo2, fm, fgcc, fgcch)
   249  	} else {
   250  		p.writeExports(fgo2, fm, fgcc, fgcch)
   251  	}
   252  
   253  	if callsMalloc && !*gccgo {
   254  		fmt.Fprint(fgo2, strings.Replace(cMallocDefGo, "PREFIX", cPrefix, -1))
   255  		fmt.Fprint(fgcc, strings.Replace(strings.Replace(cMallocDefC, "PREFIX", cPrefix, -1), "PACKED", p.packedAttribute(), -1))
   256  	}
   257  
   258  	if err := fgcc.Close(); err != nil {
   259  		fatalf("%s", err)
   260  	}
   261  	if err := fgcch.Close(); err != nil {
   262  		fatalf("%s", err)
   263  	}
   264  
   265  	if *exportHeader != "" && len(p.ExpFunc) > 0 {
   266  		fexp := creat(*exportHeader)
   267  		fgcch, err := os.Open(*objDir + "_cgo_export.h")
   268  		if err != nil {
   269  			fatalf("%s", err)
   270  		}
   271  		defer fgcch.Close()
   272  		_, err = io.Copy(fexp, fgcch)
   273  		if err != nil {
   274  			fatalf("%s", err)
   275  		}
   276  		if err = fexp.Close(); err != nil {
   277  			fatalf("%s", err)
   278  		}
   279  	}
   280  
   281  	init := gccgoInit.String()
   282  	if init != "" {
   283  		// The init function does nothing but simple
   284  		// assignments, so it won't use much stack space, so
   285  		// it's OK to not split the stack. Splitting the stack
   286  		// can run into a bug in clang (as of 2018-11-09):
   287  		// this is a leaf function, and when clang sees a leaf
   288  		// function it won't emit the split stack prologue for
   289  		// the function. However, if this function refers to a
   290  		// non-split-stack function, which will happen if the
   291  		// cgo code refers to a C function not compiled with
   292  		// -fsplit-stack, then the linker will think that it
   293  		// needs to adjust the split stack prologue, but there
   294  		// won't be one. Marking the function explicitly
   295  		// no_split_stack works around this problem by telling
   296  		// the linker that it's OK if there is no split stack
   297  		// prologue.
   298  		fmt.Fprintln(fc, "static void init(void) __attribute__ ((constructor, no_split_stack));")
   299  		fmt.Fprintln(fc, "static void init(void) {")
   300  		fmt.Fprint(fc, init)
   301  		fmt.Fprintln(fc, "}")
   302  	}
   303  }
   304  
   305  // elfImportedSymbols is like elf.File.ImportedSymbols, but it
   306  // includes weak symbols.
   307  //
   308  // A bug in some versions of LLD (at least LLD 8) cause it to emit
   309  // several pthreads symbols as weak, but we need to import those. See
   310  // issue #31912 or https://bugs.llvm.org/show_bug.cgi?id=42442.
   311  //
   312  // When doing external linking, we hand everything off to the external
   313  // linker, which will create its own dynamic symbol tables. For
   314  // internal linking, this may turn weak imports into strong imports,
   315  // which could cause dynamic linking to fail if a symbol really isn't
   316  // defined. However, the standard library depends on everything it
   317  // imports, and this is the primary use of dynamic symbol tables with
   318  // internal linking.
   319  func elfImportedSymbols(f *elf.File) []elf.ImportedSymbol {
   320  	syms, _ := f.DynamicSymbols()
   321  	var imports []elf.ImportedSymbol
   322  	for _, s := range syms {
   323  		if (elf.ST_BIND(s.Info) == elf.STB_GLOBAL || elf.ST_BIND(s.Info) == elf.STB_WEAK) && s.Section == elf.SHN_UNDEF {
   324  			imports = append(imports, elf.ImportedSymbol{
   325  				Name:    s.Name,
   326  				Library: s.Library,
   327  				Version: s.Version,
   328  			})
   329  		}
   330  	}
   331  	return imports
   332  }
   333  
   334  func dynimport(obj string) {
   335  	stdout := os.Stdout
   336  	if *dynout != "" {
   337  		f, err := os.Create(*dynout)
   338  		if err != nil {
   339  			fatalf("%s", err)
   340  		}
   341  		defer func() {
   342  			if err = f.Close(); err != nil {
   343  				fatalf("error closing %s: %v", *dynout, err)
   344  			}
   345  		}()
   346  
   347  		stdout = f
   348  	}
   349  
   350  	fmt.Fprintf(stdout, "package %s\n", *dynpackage)
   351  
   352  	if f, err := elf.Open(obj); err == nil {
   353  		defer f.Close()
   354  		if *dynlinker {
   355  			// Emit the cgo_dynamic_linker line.
   356  			if sec := f.Section(".interp"); sec != nil {
   357  				if data, err := sec.Data(); err == nil && len(data) > 1 {
   358  					// skip trailing \0 in data
   359  					fmt.Fprintf(stdout, "//go:cgo_dynamic_linker %q\n", string(data[:len(data)-1]))
   360  				}
   361  			}
   362  		}
   363  		sym := elfImportedSymbols(f)
   364  		for _, s := range sym {
   365  			targ := s.Name
   366  			if s.Version != "" {
   367  				targ += "#" + s.Version
   368  			}
   369  			checkImportSymName(s.Name)
   370  			checkImportSymName(targ)
   371  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", s.Name, targ, s.Library)
   372  		}
   373  		lib, _ := f.ImportedLibraries()
   374  		for _, l := range lib {
   375  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic _ _ %q\n", l)
   376  		}
   377  		return
   378  	}
   379  
   380  	if f, err := macho.Open(obj); err == nil {
   381  		defer f.Close()
   382  		sym, _ := f.ImportedSymbols()
   383  		for _, s := range sym {
   384  			s = strings.TrimPrefix(s, "_")
   385  			checkImportSymName(s)
   386  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", s, s, "")
   387  		}
   388  		lib, _ := f.ImportedLibraries()
   389  		for _, l := range lib {
   390  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic _ _ %q\n", l)
   391  		}
   392  		return
   393  	}
   394  
   395  	if f, err := pe.Open(obj); err == nil {
   396  		defer f.Close()
   397  		sym, _ := f.ImportedSymbols()
   398  		for _, s := range sym {
   399  			ss := strings.Split(s, ":")
   400  			name := strings.Split(ss[0], "@")[0]
   401  			checkImportSymName(name)
   402  			checkImportSymName(ss[0])
   403  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", name, ss[0], strings.ToLower(ss[1]))
   404  		}
   405  		return
   406  	}
   407  
   408  	if f, err := xcoff.Open(obj); err == nil {
   409  		defer f.Close()
   410  		sym, err := f.ImportedSymbols()
   411  		if err != nil {
   412  			fatalf("cannot load imported symbols from XCOFF file %s: %v", obj, err)
   413  		}
   414  		for _, s := range sym {
   415  			if s.Name == "runtime_rt0_go" || s.Name == "_rt0_ppc64_aix_lib" {
   416  				// These symbols are imported by runtime/cgo but
   417  				// must not be added to _cgo_import.go as there are
   418  				// Go symbols.
   419  				continue
   420  			}
   421  			checkImportSymName(s.Name)
   422  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic %s %s %q\n", s.Name, s.Name, s.Library)
   423  		}
   424  		lib, err := f.ImportedLibraries()
   425  		if err != nil {
   426  			fatalf("cannot load imported libraries from XCOFF file %s: %v", obj, err)
   427  		}
   428  		for _, l := range lib {
   429  			fmt.Fprintf(stdout, "//go:cgo_import_dynamic _ _ %q\n", l)
   430  		}
   431  		return
   432  	}
   433  
   434  	fatalf("cannot parse %s as ELF, Mach-O, PE or XCOFF", obj)
   435  }
   436  
   437  // checkImportSymName checks a symbol name we are going to emit as part
   438  // of a //go:cgo_import_dynamic pragma. These names come from object
   439  // files, so they may be corrupt. We are going to emit them unquoted,
   440  // so while they don't need to be valid symbol names (and in some cases,
   441  // involving symbol versions, they won't be) they must contain only
   442  // graphic characters and must not contain Go comments.
   443  func checkImportSymName(s string) {
   444  	for _, c := range s {
   445  		if !unicode.IsGraphic(c) || unicode.IsSpace(c) {
   446  			fatalf("dynamic symbol %q contains unsupported character", s)
   447  		}
   448  	}
   449  	if strings.Contains(s, "//") || strings.Contains(s, "/*") {
   450  		fatalf("dynamic symbol %q contains Go comment", s)
   451  	}
   452  }
   453  
   454  // Construct a gcc struct matching the gc argument frame.
   455  // Assumes that in gcc, char is 1 byte, short 2 bytes, int 4 bytes, long long 8 bytes.
   456  // These assumptions are checked by the gccProlog.
   457  // Also assumes that gc convention is to word-align the
   458  // input and output parameters.
   459  func (p *Package) structType(n *Name) (string, int64) {
   460  	var buf strings.Builder
   461  	fmt.Fprint(&buf, "struct {\n")
   462  	off := int64(0)
   463  	for i, t := range n.FuncType.Params {
   464  		if off%t.Align != 0 {
   465  			pad := t.Align - off%t.Align
   466  			fmt.Fprintf(&buf, "\t\tchar __pad%d[%d];\n", off, pad)
   467  			off += pad
   468  		}
   469  		c := t.Typedef
   470  		if c == "" {
   471  			c = t.C.String()
   472  		}
   473  		fmt.Fprintf(&buf, "\t\t%s p%d;\n", c, i)
   474  		off += t.Size
   475  	}
   476  	if off%p.PtrSize != 0 {
   477  		pad := p.PtrSize - off%p.PtrSize
   478  		fmt.Fprintf(&buf, "\t\tchar __pad%d[%d];\n", off, pad)
   479  		off += pad
   480  	}
   481  	if t := n.FuncType.Result; t != nil {
   482  		if off%t.Align != 0 {
   483  			pad := t.Align - off%t.Align
   484  			fmt.Fprintf(&buf, "\t\tchar __pad%d[%d];\n", off, pad)
   485  			off += pad
   486  		}
   487  		fmt.Fprintf(&buf, "\t\t%s r;\n", t.C)
   488  		off += t.Size
   489  	}
   490  	if off%p.PtrSize != 0 {
   491  		pad := p.PtrSize - off%p.PtrSize
   492  		fmt.Fprintf(&buf, "\t\tchar __pad%d[%d];\n", off, pad)
   493  		off += pad
   494  	}
   495  	if off == 0 {
   496  		fmt.Fprintf(&buf, "\t\tchar unused;\n") // avoid empty struct
   497  	}
   498  	fmt.Fprintf(&buf, "\t}")
   499  	return buf.String(), off
   500  }
   501  
   502  func (p *Package) writeDefsFunc(fgo2 io.Writer, n *Name, callsMalloc *bool) {
   503  	name := n.Go
   504  	gtype := n.FuncType.Go
   505  	void := gtype.Results == nil || len(gtype.Results.List) == 0
   506  	if n.AddError {
   507  		// Add "error" to return type list.
   508  		// Type list is known to be 0 or 1 element - it's a C function.
   509  		err := &ast.Field{Type: ast.NewIdent("error")}
   510  		l := gtype.Results.List
   511  		if len(l) == 0 {
   512  			l = []*ast.Field{err}
   513  		} else {
   514  			l = []*ast.Field{l[0], err}
   515  		}
   516  		t := new(ast.FuncType)
   517  		*t = *gtype
   518  		t.Results = &ast.FieldList{List: l}
   519  		gtype = t
   520  	}
   521  
   522  	// Go func declaration.
   523  	d := &ast.FuncDecl{
   524  		Name: ast.NewIdent(n.Mangle),
   525  		Type: gtype,
   526  	}
   527  
   528  	// Builtins defined in the C prolog.
   529  	inProlog := builtinDefs[name] != ""
   530  	cname := fmt.Sprintf("_cgo%s%s", cPrefix, n.Mangle)
   531  	paramnames := []string(nil)
   532  	if d.Type.Params != nil {
   533  		for i, param := range d.Type.Params.List {
   534  			paramName := fmt.Sprintf("p%d", i)
   535  			param.Names = []*ast.Ident{ast.NewIdent(paramName)}
   536  			paramnames = append(paramnames, paramName)
   537  		}
   538  	}
   539  
   540  	if *gccgo {
   541  		// Gccgo style hooks.
   542  		fmt.Fprint(fgo2, "\n")
   543  		conf.Fprint(fgo2, fset, d)
   544  		fmt.Fprint(fgo2, " {\n")
   545  		if !inProlog {
   546  			fmt.Fprint(fgo2, "\tdefer syscall.CgocallDone()\n")
   547  			fmt.Fprint(fgo2, "\tsyscall.Cgocall()\n")
   548  		}
   549  		if n.AddError {
   550  			fmt.Fprint(fgo2, "\tsyscall.SetErrno(0)\n")
   551  		}
   552  		fmt.Fprint(fgo2, "\t")
   553  		if !void {
   554  			fmt.Fprint(fgo2, "r := ")
   555  		}
   556  		fmt.Fprintf(fgo2, "%s(%s)\n", cname, strings.Join(paramnames, ", "))
   557  
   558  		if n.AddError {
   559  			fmt.Fprint(fgo2, "\te := syscall.GetErrno()\n")
   560  			fmt.Fprint(fgo2, "\tif e != 0 {\n")
   561  			fmt.Fprint(fgo2, "\t\treturn ")
   562  			if !void {
   563  				fmt.Fprint(fgo2, "r, ")
   564  			}
   565  			fmt.Fprint(fgo2, "e\n")
   566  			fmt.Fprint(fgo2, "\t}\n")
   567  			fmt.Fprint(fgo2, "\treturn ")
   568  			if !void {
   569  				fmt.Fprint(fgo2, "r, ")
   570  			}
   571  			fmt.Fprint(fgo2, "nil\n")
   572  		} else if !void {
   573  			fmt.Fprint(fgo2, "\treturn r\n")
   574  		}
   575  
   576  		fmt.Fprint(fgo2, "}\n")
   577  
   578  		// declare the C function.
   579  		fmt.Fprintf(fgo2, "//extern %s\n", cname)
   580  		d.Name = ast.NewIdent(cname)
   581  		if n.AddError {
   582  			l := d.Type.Results.List
   583  			d.Type.Results.List = l[:len(l)-1]
   584  		}
   585  		conf.Fprint(fgo2, fset, d)
   586  		fmt.Fprint(fgo2, "\n")
   587  
   588  		return
   589  	}
   590  
   591  	if inProlog {
   592  		fmt.Fprint(fgo2, builtinDefs[name])
   593  		if strings.Contains(builtinDefs[name], "_cgo_cmalloc") {
   594  			*callsMalloc = true
   595  		}
   596  		return
   597  	}
   598  
   599  	// Wrapper calls into gcc, passing a pointer to the argument frame.
   600  	fmt.Fprintf(fgo2, "//go:cgo_import_static %s\n", cname)
   601  	fmt.Fprintf(fgo2, "//go:linkname __cgofn_%s %s\n", cname, cname)
   602  	fmt.Fprintf(fgo2, "var __cgofn_%s byte\n", cname)
   603  	fmt.Fprintf(fgo2, "var %s = unsafe.Pointer(&__cgofn_%s)\n", cname, cname)
   604  
   605  	nret := 0
   606  	if !void {
   607  		d.Type.Results.List[0].Names = []*ast.Ident{ast.NewIdent("r1")}
   608  		nret = 1
   609  	}
   610  	if n.AddError {
   611  		d.Type.Results.List[nret].Names = []*ast.Ident{ast.NewIdent("r2")}
   612  	}
   613  
   614  	fmt.Fprint(fgo2, "\n")
   615  	fmt.Fprint(fgo2, "//go:cgo_unsafe_args\n")
   616  	conf.Fprint(fgo2, fset, d)
   617  	fmt.Fprint(fgo2, " {\n")
   618  
   619  	// NOTE: Using uintptr to hide from escape analysis.
   620  	arg := "0"
   621  	if len(paramnames) > 0 {
   622  		arg = "uintptr(unsafe.Pointer(&p0))"
   623  	} else if !void {
   624  		arg = "uintptr(unsafe.Pointer(&r1))"
   625  	}
   626  
   627  	noCallback := p.noCallbacks[n.C]
   628  	if noCallback {
   629  		// disable cgocallback, will check it in runtime.
   630  		fmt.Fprintf(fgo2, "\t_Cgo_no_callback(true)\n")
   631  	}
   632  
   633  	prefix := ""
   634  	if n.AddError {
   635  		prefix = "errno := "
   636  	}
   637  	fmt.Fprintf(fgo2, "\t%s_cgo_runtime_cgocall(%s, %s)\n", prefix, cname, arg)
   638  	if n.AddError {
   639  		fmt.Fprintf(fgo2, "\tif errno != 0 { r2 = syscall.Errno(errno) }\n")
   640  	}
   641  	if noCallback {
   642  		fmt.Fprintf(fgo2, "\t_Cgo_no_callback(false)\n")
   643  	}
   644  
   645  	// Use _Cgo_keepalive instead of _Cgo_use when noescape & nocallback exist,
   646  	// so that the compiler won't force to escape them to heap.
   647  	// Instead, make the compiler keep them alive by using _Cgo_keepalive.
   648  	touchFunc := "_Cgo_use"
   649  	if p.noEscapes[n.C] && p.noCallbacks[n.C] {
   650  		touchFunc = "_Cgo_keepalive"
   651  	}
   652  	fmt.Fprintf(fgo2, "\tif _Cgo_always_false {\n")
   653  	if d.Type.Params != nil {
   654  		for _, name := range paramnames {
   655  			fmt.Fprintf(fgo2, "\t\t%s(%s)\n", touchFunc, name)
   656  		}
   657  	}
   658  	fmt.Fprintf(fgo2, "\t}\n")
   659  	fmt.Fprintf(fgo2, "\treturn\n")
   660  	fmt.Fprintf(fgo2, "}\n")
   661  }
   662  
   663  // writeOutput creates stubs for a specific source file to be compiled by gc
   664  func (p *Package) writeOutput(f *File, srcfile string) {
   665  	base := srcfile
   666  	base = strings.TrimSuffix(base, ".go")
   667  	base = filepath.Base(base)
   668  	fgo1 := creat(*objDir + base + ".cgo1.go")
   669  	fgcc := creat(*objDir + base + ".cgo2.c")
   670  
   671  	p.GoFiles = append(p.GoFiles, base+".cgo1.go")
   672  	p.GccFiles = append(p.GccFiles, base+".cgo2.c")
   673  
   674  	// Write Go output: Go input with rewrites of C.xxx to _C_xxx.
   675  	fmt.Fprintf(fgo1, "// Code generated by cmd/cgo; DO NOT EDIT.\n\n")
   676  	if strings.ContainsAny(srcfile, "\r\n") {
   677  		// This should have been checked when the file path was first resolved,
   678  		// but we double check here just to be sure.
   679  		fatalf("internal error: writeOutput: srcfile contains unexpected newline character: %q", srcfile)
   680  	}
   681  	fmt.Fprintf(fgo1, "//line %s:1:1\n", srcfile)
   682  	fgo1.Write(f.Edit.Bytes())
   683  
   684  	// While we process the vars and funcs, also write gcc output.
   685  	// Gcc output starts with the preamble.
   686  	fmt.Fprintf(fgcc, "%s\n", builtinProlog)
   687  	fmt.Fprintf(fgcc, "%s\n", f.Preamble)
   688  	fmt.Fprintf(fgcc, "%s\n", gccProlog)
   689  	fmt.Fprintf(fgcc, "%s\n", tsanProlog)
   690  	fmt.Fprintf(fgcc, "%s\n", msanProlog)
   691  
   692  	for _, key := range nameKeys(f.Name) {
   693  		n := f.Name[key]
   694  		if n.FuncType != nil {
   695  			p.writeOutputFunc(fgcc, n)
   696  		}
   697  	}
   698  
   699  	fgo1.Close()
   700  	fgcc.Close()
   701  }
   702  
   703  // fixGo converts the internal Name.Go field into the name we should show
   704  // to users in error messages. There's only one for now: on input we rewrite
   705  // C.malloc into C._CMalloc, so change it back here.
   706  func fixGo(name string) string {
   707  	if name == "_CMalloc" {
   708  		return "malloc"
   709  	}
   710  	return name
   711  }
   712  
   713  var isBuiltin = map[string]bool{
   714  	"_Cfunc_CString":   true,
   715  	"_Cfunc_CBytes":    true,
   716  	"_Cfunc_GoString":  true,
   717  	"_Cfunc_GoStringN": true,
   718  	"_Cfunc_GoBytes":   true,
   719  	"_Cfunc__CMalloc":  true,
   720  }
   721  
   722  func (p *Package) writeOutputFunc(fgcc *os.File, n *Name) {
   723  	name := n.Mangle
   724  	if isBuiltin[name] || p.Written[name] {
   725  		// The builtins are already defined in the C prolog, and we don't
   726  		// want to duplicate function definitions we've already done.
   727  		return
   728  	}
   729  	p.Written[name] = true
   730  
   731  	if *gccgo {
   732  		p.writeGccgoOutputFunc(fgcc, n)
   733  		return
   734  	}
   735  
   736  	ctype, _ := p.structType(n)
   737  
   738  	// Gcc wrapper unpacks the C argument struct
   739  	// and calls the actual C function.
   740  	fmt.Fprintf(fgcc, "CGO_NO_SANITIZE_THREAD\n")
   741  	if n.AddError {
   742  		fmt.Fprintf(fgcc, "int\n")
   743  	} else {
   744  		fmt.Fprintf(fgcc, "void\n")
   745  	}
   746  	fmt.Fprintf(fgcc, "_cgo%s%s(void *v)\n", cPrefix, n.Mangle)
   747  	fmt.Fprintf(fgcc, "{\n")
   748  	if n.AddError {
   749  		fmt.Fprintf(fgcc, "\tint _cgo_errno;\n")
   750  	}
   751  	// We're trying to write a gcc struct that matches gc's layout.
   752  	// Use packed attribute to force no padding in this struct in case
   753  	// gcc has different packing requirements.
   754  	fmt.Fprintf(fgcc, "\t%s %v *_cgo_a = v;\n", ctype, p.packedAttribute())
   755  	if n.FuncType.Result != nil {
   756  		// Save the stack top for use below.
   757  		fmt.Fprintf(fgcc, "\tchar *_cgo_stktop = _cgo_topofstack();\n")
   758  	}
   759  	tr := n.FuncType.Result
   760  	if tr != nil {
   761  		fmt.Fprintf(fgcc, "\t__typeof__(_cgo_a->r) _cgo_r;\n")
   762  	}
   763  	fmt.Fprintf(fgcc, "\t_cgo_tsan_acquire();\n")
   764  	if n.AddError {
   765  		fmt.Fprintf(fgcc, "\terrno = 0;\n")
   766  	}
   767  	fmt.Fprintf(fgcc, "\t")
   768  	if tr != nil {
   769  		fmt.Fprintf(fgcc, "_cgo_r = ")
   770  		if c := tr.C.String(); c[len(c)-1] == '*' {
   771  			fmt.Fprint(fgcc, "(__typeof__(_cgo_a->r)) ")
   772  		}
   773  	}
   774  	if n.Kind == "macro" {
   775  		fmt.Fprintf(fgcc, "%s;\n", n.C)
   776  	} else {
   777  		fmt.Fprintf(fgcc, "%s(", n.C)
   778  		for i := range n.FuncType.Params {
   779  			if i > 0 {
   780  				fmt.Fprintf(fgcc, ", ")
   781  			}
   782  			fmt.Fprintf(fgcc, "_cgo_a->p%d", i)
   783  		}
   784  		fmt.Fprintf(fgcc, ");\n")
   785  	}
   786  	if n.AddError {
   787  		fmt.Fprintf(fgcc, "\t_cgo_errno = errno;\n")
   788  	}
   789  	fmt.Fprintf(fgcc, "\t_cgo_tsan_release();\n")
   790  	if n.FuncType.Result != nil {
   791  		// The cgo call may have caused a stack copy (via a callback).
   792  		// Adjust the return value pointer appropriately.
   793  		fmt.Fprintf(fgcc, "\t_cgo_a = (void*)((char*)_cgo_a + (_cgo_topofstack() - _cgo_stktop));\n")
   794  		// Save the return value.
   795  		fmt.Fprintf(fgcc, "\t_cgo_a->r = _cgo_r;\n")
   796  		// The return value is on the Go stack. If we are using msan,
   797  		// and if the C value is partially or completely uninitialized,
   798  		// the assignment will mark the Go stack as uninitialized.
   799  		// The Go compiler does not update msan for changes to the
   800  		// stack. It is possible that the stack will remain
   801  		// uninitialized, and then later be used in a way that is
   802  		// visible to msan, possibly leading to a false positive.
   803  		// Mark the stack space as written, to avoid this problem.
   804  		// See issue 26209.
   805  		fmt.Fprintf(fgcc, "\t_cgo_msan_write(&_cgo_a->r, sizeof(_cgo_a->r));\n")
   806  	}
   807  	if n.AddError {
   808  		fmt.Fprintf(fgcc, "\treturn _cgo_errno;\n")
   809  	}
   810  	fmt.Fprintf(fgcc, "}\n")
   811  	fmt.Fprintf(fgcc, "\n")
   812  }
   813  
   814  // Write out a wrapper for a function when using gccgo. This is a
   815  // simple wrapper that just calls the real function. We only need a
   816  // wrapper to support static functions in the prologue--without a
   817  // wrapper, we can't refer to the function, since the reference is in
   818  // a different file.
   819  func (p *Package) writeGccgoOutputFunc(fgcc *os.File, n *Name) {
   820  	fmt.Fprintf(fgcc, "CGO_NO_SANITIZE_THREAD\n")
   821  	if t := n.FuncType.Result; t != nil {
   822  		fmt.Fprintf(fgcc, "%s\n", t.C.String())
   823  	} else {
   824  		fmt.Fprintf(fgcc, "void\n")
   825  	}
   826  	fmt.Fprintf(fgcc, "_cgo%s%s(", cPrefix, n.Mangle)
   827  	for i, t := range n.FuncType.Params {
   828  		if i > 0 {
   829  			fmt.Fprintf(fgcc, ", ")
   830  		}
   831  		c := t.Typedef
   832  		if c == "" {
   833  			c = t.C.String()
   834  		}
   835  		fmt.Fprintf(fgcc, "%s p%d", c, i)
   836  	}
   837  	fmt.Fprintf(fgcc, ")\n")
   838  	fmt.Fprintf(fgcc, "{\n")
   839  	if t := n.FuncType.Result; t != nil {
   840  		fmt.Fprintf(fgcc, "\t%s _cgo_r;\n", t.C.String())
   841  	}
   842  	fmt.Fprintf(fgcc, "\t_cgo_tsan_acquire();\n")
   843  	fmt.Fprintf(fgcc, "\t")
   844  	if t := n.FuncType.Result; t != nil {
   845  		fmt.Fprintf(fgcc, "_cgo_r = ")
   846  		// Cast to void* to avoid warnings due to omitted qualifiers.
   847  		if c := t.C.String(); c[len(c)-1] == '*' {
   848  			fmt.Fprintf(fgcc, "(void*)")
   849  		}
   850  	}
   851  	if n.Kind == "macro" {
   852  		fmt.Fprintf(fgcc, "%s;\n", n.C)
   853  	} else {
   854  		fmt.Fprintf(fgcc, "%s(", n.C)
   855  		for i := range n.FuncType.Params {
   856  			if i > 0 {
   857  				fmt.Fprintf(fgcc, ", ")
   858  			}
   859  			fmt.Fprintf(fgcc, "p%d", i)
   860  		}
   861  		fmt.Fprintf(fgcc, ");\n")
   862  	}
   863  	fmt.Fprintf(fgcc, "\t_cgo_tsan_release();\n")
   864  	if t := n.FuncType.Result; t != nil {
   865  		fmt.Fprintf(fgcc, "\treturn ")
   866  		// Cast to void* to avoid warnings due to omitted qualifiers
   867  		// and explicit incompatible struct types.
   868  		if c := t.C.String(); c[len(c)-1] == '*' {
   869  			fmt.Fprintf(fgcc, "(void*)")
   870  		}
   871  		fmt.Fprintf(fgcc, "_cgo_r;\n")
   872  	}
   873  	fmt.Fprintf(fgcc, "}\n")
   874  	fmt.Fprintf(fgcc, "\n")
   875  }
   876  
   877  // packedAttribute returns host compiler struct attribute that will be
   878  // used to match gc's struct layout. For example, on 386 Windows,
   879  // gcc wants to 8-align int64s, but gc does not.
   880  // Use __gcc_struct__ to work around https://gcc.gnu.org/PR52991 on x86,
   881  // and https://golang.org/issue/5603.
   882  func (p *Package) packedAttribute() string {
   883  	s := "__attribute__((__packed__"
   884  	if !p.GccIsClang && (goarch == "amd64" || goarch == "386") {
   885  		s += ", __gcc_struct__"
   886  	}
   887  	return s + "))"
   888  }
   889  
   890  // exportParamName returns the value of param as it should be
   891  // displayed in a c header file. If param contains any non-ASCII
   892  // characters, this function will return the character p followed by
   893  // the value of position; otherwise, this function will return the
   894  // value of param.
   895  func exportParamName(param string, position int) string {
   896  	if param == "" {
   897  		return fmt.Sprintf("p%d", position)
   898  	}
   899  
   900  	pname := param
   901  
   902  	for i := 0; i < len(param); i++ {
   903  		if param[i] > unicode.MaxASCII {
   904  			pname = fmt.Sprintf("p%d", position)
   905  			break
   906  		}
   907  	}
   908  
   909  	return pname
   910  }
   911  
   912  // Write out the various stubs we need to support functions exported
   913  // from Go so that they are callable from C.
   914  func (p *Package) writeExports(fgo2, fm, fgcc, fgcch io.Writer) {
   915  	p.writeExportHeader(fgcch)
   916  
   917  	fmt.Fprintf(fgcc, "/* Code generated by cmd/cgo; DO NOT EDIT. */\n\n")
   918  	fmt.Fprintf(fgcc, "#include <stdlib.h>\n")
   919  	fmt.Fprintf(fgcc, "#include \"_cgo_export.h\"\n\n")
   920  
   921  	// We use packed structs, but they are always aligned.
   922  	// The pragmas and address-of-packed-member are only recognized as
   923  	// warning groups in clang 4.0+, so ignore unknown pragmas first.
   924  	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Wunknown-pragmas\"\n")
   925  	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Wpragmas\"\n")
   926  	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Waddress-of-packed-member\"\n")
   927  	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Wunknown-warning-option\"\n")
   928  	fmt.Fprintf(fgcc, "#pragma GCC diagnostic ignored \"-Wunaligned-access\"\n")
   929  
   930  	fmt.Fprintf(fgcc, "extern void crosscall2(void (*fn)(void *), void *, int, size_t);\n")
   931  	fmt.Fprintf(fgcc, "extern size_t _cgo_wait_runtime_init_done(void);\n")
   932  	fmt.Fprintf(fgcc, "extern void _cgo_release_context(size_t);\n\n")
   933  	fmt.Fprintf(fgcc, "extern char* _cgo_topofstack(void);")
   934  	fmt.Fprintf(fgcc, "%s\n", tsanProlog)
   935  	fmt.Fprintf(fgcc, "%s\n", msanProlog)
   936  
   937  	for _, exp := range p.ExpFunc {
   938  		fn := exp.Func
   939  
   940  		// Construct a struct that will be used to communicate
   941  		// arguments from C to Go. The C and Go definitions
   942  		// just have to agree. The gcc struct will be compiled
   943  		// with __attribute__((packed)) so all padding must be
   944  		// accounted for explicitly.
   945  		var ctype strings.Builder
   946  		const start = "struct {\n"
   947  		ctype.WriteString(start)
   948  		gotype := new(bytes.Buffer)
   949  		fmt.Fprintf(gotype, "struct {\n")
   950  		off := int64(0)
   951  		npad := 0
   952  		argField := func(typ ast.Expr, namePat string, args ...interface{}) {
   953  			name := fmt.Sprintf(namePat, args...)
   954  			t := p.cgoType(typ)
   955  			if off%t.Align != 0 {
   956  				pad := t.Align - off%t.Align
   957  				fmt.Fprintf(&ctype, "\t\tchar __pad%d[%d];\n", npad, pad)
   958  				off += pad
   959  				npad++
   960  			}
   961  			fmt.Fprintf(&ctype, "\t\t%s %s;\n", t.C, name)
   962  			fmt.Fprintf(gotype, "\t\t%s ", name)
   963  			noSourceConf.Fprint(gotype, fset, typ)
   964  			fmt.Fprintf(gotype, "\n")
   965  			off += t.Size
   966  		}
   967  		if fn.Recv != nil {
   968  			argField(fn.Recv.List[0].Type, "recv")
   969  		}
   970  		fntype := fn.Type
   971  		forFieldList(fntype.Params,
   972  			func(i int, aname string, atype ast.Expr) {
   973  				argField(atype, "p%d", i)
   974  			})
   975  		forFieldList(fntype.Results,
   976  			func(i int, aname string, atype ast.Expr) {
   977  				argField(atype, "r%d", i)
   978  			})
   979  		if ctype.Len() == len(start) {
   980  			ctype.WriteString("\t\tchar unused;\n") // avoid empty struct
   981  		}
   982  		ctype.WriteString("\t}")
   983  		fmt.Fprintf(gotype, "\t}")
   984  
   985  		// Get the return type of the wrapper function
   986  		// compiled by gcc.
   987  		gccResult := ""
   988  		if fntype.Results == nil || len(fntype.Results.List) == 0 {
   989  			gccResult = "void"
   990  		} else if len(fntype.Results.List) == 1 && len(fntype.Results.List[0].Names) <= 1 {
   991  			gccResult = p.cgoType(fntype.Results.List[0].Type).C.String()
   992  		} else {
   993  			fmt.Fprintf(fgcch, "\n/* Return type for %s */\n", exp.ExpName)
   994  			fmt.Fprintf(fgcch, "struct %s_return {\n", exp.ExpName)
   995  			forFieldList(fntype.Results,
   996  				func(i int, aname string, atype ast.Expr) {
   997  					fmt.Fprintf(fgcch, "\t%s r%d;", p.cgoType(atype).C, i)
   998  					if len(aname) > 0 {
   999  						fmt.Fprintf(fgcch, " /* %s */", aname)
  1000  					}
  1001  					fmt.Fprint(fgcch, "\n")
  1002  				})
  1003  			fmt.Fprintf(fgcch, "};\n")
  1004  			gccResult = "struct " + exp.ExpName + "_return"
  1005  		}
  1006  
  1007  		// Build the wrapper function compiled by gcc.
  1008  		gccExport := ""
  1009  		if goos == "windows" {
  1010  			gccExport = "__declspec(dllexport) "
  1011  		}
  1012  		var s strings.Builder
  1013  		fmt.Fprintf(&s, "%s%s %s(", gccExport, gccResult, exp.ExpName)
  1014  		if fn.Recv != nil {
  1015  			s.WriteString(p.cgoType(fn.Recv.List[0].Type).C.String())
  1016  			s.WriteString(" recv")
  1017  		}
  1018  
  1019  		if len(fntype.Params.List) > 0 {
  1020  			forFieldList(fntype.Params,
  1021  				func(i int, aname string, atype ast.Expr) {
  1022  					if i > 0 || fn.Recv != nil {
  1023  						s.WriteString(", ")
  1024  					}
  1025  					fmt.Fprintf(&s, "%s %s", p.cgoType(atype).C, exportParamName(aname, i))
  1026  				})
  1027  		} else {
  1028  			s.WriteString("void")
  1029  		}
  1030  		s.WriteByte(')')
  1031  
  1032  		if len(exp.Doc) > 0 {
  1033  			fmt.Fprintf(fgcch, "\n%s", exp.Doc)
  1034  			if !strings.HasSuffix(exp.Doc, "\n") {
  1035  				fmt.Fprint(fgcch, "\n")
  1036  			}
  1037  		}
  1038  		fmt.Fprintf(fgcch, "extern %s;\n", s.String())
  1039  
  1040  		fmt.Fprintf(fgcc, "extern void _cgoexp%s_%s(void *);\n", cPrefix, exp.ExpName)
  1041  		fmt.Fprintf(fgcc, "\nCGO_NO_SANITIZE_THREAD")
  1042  		fmt.Fprintf(fgcc, "\n%s\n", s.String())
  1043  		fmt.Fprintf(fgcc, "{\n")
  1044  		fmt.Fprintf(fgcc, "\tsize_t _cgo_ctxt = _cgo_wait_runtime_init_done();\n")
  1045  		// The results part of the argument structure must be
  1046  		// initialized to 0 so the write barriers generated by
  1047  		// the assignments to these fields in Go are safe.
  1048  		//
  1049  		// We use a local static variable to get the zeroed
  1050  		// value of the argument type. This avoids including
  1051  		// string.h for memset, and is also robust to C++
  1052  		// types with constructors. Both GCC and LLVM optimize
  1053  		// this into just zeroing _cgo_a.
  1054  		fmt.Fprintf(fgcc, "\ttypedef %s %v _cgo_argtype;\n", ctype.String(), p.packedAttribute())
  1055  		fmt.Fprintf(fgcc, "\tstatic _cgo_argtype _cgo_zero;\n")
  1056  		fmt.Fprintf(fgcc, "\t_cgo_argtype _cgo_a = _cgo_zero;\n")
  1057  		if gccResult != "void" && (len(fntype.Results.List) > 1 || len(fntype.Results.List[0].Names) > 1) {
  1058  			fmt.Fprintf(fgcc, "\t%s r;\n", gccResult)
  1059  		}
  1060  		if fn.Recv != nil {
  1061  			fmt.Fprintf(fgcc, "\t_cgo_a.recv = recv;\n")
  1062  		}
  1063  		forFieldList(fntype.Params,
  1064  			func(i int, aname string, atype ast.Expr) {
  1065  				fmt.Fprintf(fgcc, "\t_cgo_a.p%d = %s;\n", i, exportParamName(aname, i))
  1066  			})
  1067  		fmt.Fprintf(fgcc, "\t_cgo_tsan_release();\n")
  1068  		fmt.Fprintf(fgcc, "\tcrosscall2(_cgoexp%s_%s, &_cgo_a, %d, _cgo_ctxt);\n", cPrefix, exp.ExpName, off)
  1069  		fmt.Fprintf(fgcc, "\t_cgo_tsan_acquire();\n")
  1070  		fmt.Fprintf(fgcc, "\t_cgo_release_context(_cgo_ctxt);\n")
  1071  		if gccResult != "void" {
  1072  			if len(fntype.Results.List) == 1 && len(fntype.Results.List[0].Names) <= 1 {
  1073  				fmt.Fprintf(fgcc, "\treturn _cgo_a.r0;\n")
  1074  			} else {
  1075  				forFieldList(fntype.Results,
  1076  					func(i int, aname string, atype ast.Expr) {
  1077  						fmt.Fprintf(fgcc, "\tr.r%d = _cgo_a.r%d;\n", i, i)
  1078  					})
  1079  				fmt.Fprintf(fgcc, "\treturn r;\n")
  1080  			}
  1081  		}
  1082  		fmt.Fprintf(fgcc, "}\n")
  1083  
  1084  		// In internal linking mode, the Go linker sees both
  1085  		// the C wrapper written above and the Go wrapper it
  1086  		// references. Hence, export the C wrapper (e.g., for
  1087  		// if we're building a shared object). The Go linker
  1088  		// will resolve the C wrapper's reference to the Go
  1089  		// wrapper without a separate export.
  1090  		fmt.Fprintf(fgo2, "//go:cgo_export_dynamic %s\n", exp.ExpName)
  1091  		// cgo_export_static refers to a symbol by its linker
  1092  		// name, so set the linker name of the Go wrapper.
  1093  		fmt.Fprintf(fgo2, "//go:linkname _cgoexp%s_%s _cgoexp%s_%s\n", cPrefix, exp.ExpName, cPrefix, exp.ExpName)
  1094  		// In external linking mode, the Go linker sees the Go
  1095  		// wrapper, but not the C wrapper. For this case,
  1096  		// export the Go wrapper so the host linker can
  1097  		// resolve the reference from the C wrapper to the Go
  1098  		// wrapper.
  1099  		fmt.Fprintf(fgo2, "//go:cgo_export_static _cgoexp%s_%s\n", cPrefix, exp.ExpName)
  1100  
  1101  		// Build the wrapper function compiled by cmd/compile.
  1102  		// This unpacks the argument struct above and calls the Go function.
  1103  		fmt.Fprintf(fgo2, "func _cgoexp%s_%s(a *%s) {\n", cPrefix, exp.ExpName, gotype)
  1104  
  1105  		fmt.Fprintf(fm, "void _cgoexp%s_%s(void* p __attribute__((unused))){}\n", cPrefix, exp.ExpName)
  1106  
  1107  		fmt.Fprintf(fgo2, "\t")
  1108  
  1109  		if gccResult != "void" {
  1110  			// Write results back to frame.
  1111  			forFieldList(fntype.Results,
  1112  				func(i int, aname string, atype ast.Expr) {
  1113  					if i > 0 {
  1114  						fmt.Fprintf(fgo2, ", ")
  1115  					}
  1116  					fmt.Fprintf(fgo2, "a.r%d", i)
  1117  				})
  1118  			fmt.Fprintf(fgo2, " = ")
  1119  		}
  1120  		if fn.Recv != nil {
  1121  			fmt.Fprintf(fgo2, "a.recv.")
  1122  		}
  1123  		fmt.Fprintf(fgo2, "%s(", exp.Func.Name)
  1124  		forFieldList(fntype.Params,
  1125  			func(i int, aname string, atype ast.Expr) {
  1126  				if i > 0 {
  1127  					fmt.Fprint(fgo2, ", ")
  1128  				}
  1129  				fmt.Fprintf(fgo2, "a.p%d", i)
  1130  			})
  1131  		fmt.Fprint(fgo2, ")\n")
  1132  		if gccResult != "void" {
  1133  			// Verify that any results don't contain any
  1134  			// Go pointers.
  1135  			forFieldList(fntype.Results,
  1136  				func(i int, aname string, atype ast.Expr) {
  1137  					if !p.hasPointer(nil, atype, false) {
  1138  						return
  1139  					}
  1140  					fmt.Fprintf(fgo2, "\t_cgoCheckResult(a.r%d)\n", i)
  1141  				})
  1142  		}
  1143  		fmt.Fprint(fgo2, "}\n")
  1144  	}
  1145  
  1146  	fmt.Fprintf(fgcch, "%s", gccExportHeaderEpilog)
  1147  }
  1148  
  1149  // Write out the C header allowing C code to call exported gccgo functions.
  1150  func (p *Package) writeGccgoExports(fgo2, fm, fgcc, fgcch io.Writer) {
  1151  	gccgoSymbolPrefix := p.gccgoSymbolPrefix()
  1152  
  1153  	p.writeExportHeader(fgcch)
  1154  
  1155  	fmt.Fprintf(fgcc, "/* Code generated by cmd/cgo; DO NOT EDIT. */\n\n")
  1156  	fmt.Fprintf(fgcc, "#include \"_cgo_export.h\"\n")
  1157  
  1158  	fmt.Fprintf(fgcc, "%s\n", gccgoExportFileProlog)
  1159  	fmt.Fprintf(fgcc, "%s\n", tsanProlog)
  1160  	fmt.Fprintf(fgcc, "%s\n", msanProlog)
  1161  
  1162  	for _, exp := range p.ExpFunc {
  1163  		fn := exp.Func
  1164  		fntype := fn.Type
  1165  
  1166  		cdeclBuf := new(strings.Builder)
  1167  		resultCount := 0
  1168  		forFieldList(fntype.Results,
  1169  			func(i int, aname string, atype ast.Expr) { resultCount++ })
  1170  		switch resultCount {
  1171  		case 0:
  1172  			fmt.Fprintf(cdeclBuf, "void")
  1173  		case 1:
  1174  			forFieldList(fntype.Results,
  1175  				func(i int, aname string, atype ast.Expr) {
  1176  					t := p.cgoType(atype)
  1177  					fmt.Fprintf(cdeclBuf, "%s", t.C)
  1178  				})
  1179  		default:
  1180  			// Declare a result struct.
  1181  			fmt.Fprintf(fgcch, "\n/* Return type for %s */\n", exp.ExpName)
  1182  			fmt.Fprintf(fgcch, "struct %s_return {\n", exp.ExpName)
  1183  			forFieldList(fntype.Results,
  1184  				func(i int, aname string, atype ast.Expr) {
  1185  					t := p.cgoType(atype)
  1186  					fmt.Fprintf(fgcch, "\t%s r%d;", t.C, i)
  1187  					if len(aname) > 0 {
  1188  						fmt.Fprintf(fgcch, " /* %s */", aname)
  1189  					}
  1190  					fmt.Fprint(fgcch, "\n")
  1191  				})
  1192  			fmt.Fprintf(fgcch, "};\n")
  1193  			fmt.Fprintf(cdeclBuf, "struct %s_return", exp.ExpName)
  1194  		}
  1195  
  1196  		cRet := cdeclBuf.String()
  1197  
  1198  		cdeclBuf = new(strings.Builder)
  1199  		fmt.Fprintf(cdeclBuf, "(")
  1200  		if fn.Recv != nil {
  1201  			fmt.Fprintf(cdeclBuf, "%s recv", p.cgoType(fn.Recv.List[0].Type).C.String())
  1202  		}
  1203  		// Function parameters.
  1204  		forFieldList(fntype.Params,
  1205  			func(i int, aname string, atype ast.Expr) {
  1206  				if i > 0 || fn.Recv != nil {
  1207  					fmt.Fprintf(cdeclBuf, ", ")
  1208  				}
  1209  				t := p.cgoType(atype)
  1210  				fmt.Fprintf(cdeclBuf, "%s p%d", t.C, i)
  1211  			})
  1212  		fmt.Fprintf(cdeclBuf, ")")
  1213  		cParams := cdeclBuf.String()
  1214  
  1215  		if len(exp.Doc) > 0 {
  1216  			fmt.Fprintf(fgcch, "\n%s", exp.Doc)
  1217  		}
  1218  
  1219  		fmt.Fprintf(fgcch, "extern %s %s%s;\n", cRet, exp.ExpName, cParams)
  1220  
  1221  		// We need to use a name that will be exported by the
  1222  		// Go code; otherwise gccgo will make it static and we
  1223  		// will not be able to link against it from the C
  1224  		// code.
  1225  		goName := "Cgoexp_" + exp.ExpName
  1226  		fmt.Fprintf(fgcc, `extern %s %s %s __asm__("%s.%s");`, cRet, goName, cParams, gccgoSymbolPrefix, gccgoToSymbol(goName))
  1227  		fmt.Fprint(fgcc, "\n")
  1228  
  1229  		fmt.Fprint(fgcc, "\nCGO_NO_SANITIZE_THREAD\n")
  1230  		fmt.Fprintf(fgcc, "%s %s %s {\n", cRet, exp.ExpName, cParams)
  1231  		if resultCount > 0 {
  1232  			fmt.Fprintf(fgcc, "\t%s r;\n", cRet)
  1233  		}
  1234  		fmt.Fprintf(fgcc, "\tif(_cgo_wait_runtime_init_done)\n")
  1235  		fmt.Fprintf(fgcc, "\t\t_cgo_wait_runtime_init_done();\n")
  1236  		fmt.Fprintf(fgcc, "\t_cgo_tsan_release();\n")
  1237  		fmt.Fprint(fgcc, "\t")
  1238  		if resultCount > 0 {
  1239  			fmt.Fprint(fgcc, "r = ")
  1240  		}
  1241  		fmt.Fprintf(fgcc, "%s(", goName)
  1242  		if fn.Recv != nil {
  1243  			fmt.Fprint(fgcc, "recv")
  1244  		}
  1245  		forFieldList(fntype.Params,
  1246  			func(i int, aname string, atype ast.Expr) {
  1247  				if i > 0 || fn.Recv != nil {
  1248  					fmt.Fprintf(fgcc, ", ")
  1249  				}
  1250  				fmt.Fprintf(fgcc, "p%d", i)
  1251  			})
  1252  		fmt.Fprint(fgcc, ");\n")
  1253  		fmt.Fprintf(fgcc, "\t_cgo_tsan_acquire();\n")
  1254  		if resultCount > 0 {
  1255  			fmt.Fprint(fgcc, "\treturn r;\n")
  1256  		}
  1257  		fmt.Fprint(fgcc, "}\n")
  1258  
  1259  		// Dummy declaration for _cgo_main.c
  1260  		fmt.Fprintf(fm, `char %s[1] __asm__("%s.%s");`, goName, gccgoSymbolPrefix, gccgoToSymbol(goName))
  1261  		fmt.Fprint(fm, "\n")
  1262  
  1263  		// For gccgo we use a wrapper function in Go, in order
  1264  		// to call CgocallBack and CgocallBackDone.
  1265  
  1266  		// This code uses printer.Fprint, not conf.Fprint,
  1267  		// because we don't want //line comments in the middle
  1268  		// of the function types.
  1269  		fmt.Fprint(fgo2, "\n")
  1270  		fmt.Fprintf(fgo2, "func %s(", goName)
  1271  		if fn.Recv != nil {
  1272  			fmt.Fprint(fgo2, "recv ")
  1273  			printer.Fprint(fgo2, fset, fn.Recv.List[0].Type)
  1274  		}
  1275  		forFieldList(fntype.Params,
  1276  			func(i int, aname string, atype ast.Expr) {
  1277  				if i > 0 || fn.Recv != nil {
  1278  					fmt.Fprintf(fgo2, ", ")
  1279  				}
  1280  				fmt.Fprintf(fgo2, "p%d ", i)
  1281  				printer.Fprint(fgo2, fset, atype)
  1282  			})
  1283  		fmt.Fprintf(fgo2, ")")
  1284  		if resultCount > 0 {
  1285  			fmt.Fprintf(fgo2, " (")
  1286  			forFieldList(fntype.Results,
  1287  				func(i int, aname string, atype ast.Expr) {
  1288  					if i > 0 {
  1289  						fmt.Fprint(fgo2, ", ")
  1290  					}
  1291  					printer.Fprint(fgo2, fset, atype)
  1292  				})
  1293  			fmt.Fprint(fgo2, ")")
  1294  		}
  1295  		fmt.Fprint(fgo2, " {\n")
  1296  		fmt.Fprint(fgo2, "\tsyscall.CgocallBack()\n")
  1297  		fmt.Fprint(fgo2, "\tdefer syscall.CgocallBackDone()\n")
  1298  		fmt.Fprint(fgo2, "\t")
  1299  		if resultCount > 0 {
  1300  			fmt.Fprint(fgo2, "return ")
  1301  		}
  1302  		if fn.Recv != nil {
  1303  			fmt.Fprint(fgo2, "recv.")
  1304  		}
  1305  		fmt.Fprintf(fgo2, "%s(", exp.Func.Name)
  1306  		forFieldList(fntype.Params,
  1307  			func(i int, aname string, atype ast.Expr) {
  1308  				if i > 0 {
  1309  					fmt.Fprint(fgo2, ", ")
  1310  				}
  1311  				fmt.Fprintf(fgo2, "p%d", i)
  1312  			})
  1313  		fmt.Fprint(fgo2, ")\n")
  1314  		fmt.Fprint(fgo2, "}\n")
  1315  	}
  1316  
  1317  	fmt.Fprintf(fgcch, "%s", gccExportHeaderEpilog)
  1318  }
  1319  
  1320  // writeExportHeader writes out the start of the _cgo_export.h file.
  1321  func (p *Package) writeExportHeader(fgcch io.Writer) {
  1322  	fmt.Fprintf(fgcch, "/* Code generated by cmd/cgo; DO NOT EDIT. */\n\n")
  1323  	pkg := *importPath
  1324  	if pkg == "" {
  1325  		pkg = p.PackagePath
  1326  	}
  1327  	fmt.Fprintf(fgcch, "/* package %s */\n\n", pkg)
  1328  	fmt.Fprintf(fgcch, "%s\n", builtinExportProlog)
  1329  
  1330  	// Remove absolute paths from #line comments in the preamble.
  1331  	// They aren't useful for people using the header file,
  1332  	// and they mean that the header files change based on the
  1333  	// exact location of GOPATH.
  1334  	re := regexp.MustCompile(`(?m)^(#line\s+\d+\s+")[^"]*[/\\]([^"]*")`)
  1335  	preamble := re.ReplaceAllString(p.Preamble, "$1$2")
  1336  
  1337  	fmt.Fprintf(fgcch, "/* Start of preamble from import \"C\" comments.  */\n\n")
  1338  	fmt.Fprintf(fgcch, "%s\n", preamble)
  1339  	fmt.Fprintf(fgcch, "\n/* End of preamble from import \"C\" comments.  */\n\n")
  1340  
  1341  	fmt.Fprintf(fgcch, "%s\n", p.gccExportHeaderProlog())
  1342  }
  1343  
  1344  // gccgoToSymbol converts a name to a mangled symbol for gccgo.
  1345  func gccgoToSymbol(ppath string) string {
  1346  	if gccgoMangler == nil {
  1347  		var err error
  1348  		cmd := os.Getenv("GCCGO")
  1349  		if cmd == "" {
  1350  			cmd, err = exec.LookPath("gccgo")
  1351  			if err != nil {
  1352  				fatalf("unable to locate gccgo: %v", err)
  1353  			}
  1354  		}
  1355  		gccgoMangler, err = pkgpath.ToSymbolFunc(cmd, *objDir)
  1356  		if err != nil {
  1357  			fatalf("%v", err)
  1358  		}
  1359  	}
  1360  	return gccgoMangler(ppath)
  1361  }
  1362  
  1363  // Return the package prefix when using gccgo.
  1364  func (p *Package) gccgoSymbolPrefix() string {
  1365  	if !*gccgo {
  1366  		return ""
  1367  	}
  1368  
  1369  	if *gccgopkgpath != "" {
  1370  		return gccgoToSymbol(*gccgopkgpath)
  1371  	}
  1372  	if *gccgoprefix == "" && p.PackageName == "main" {
  1373  		return "main"
  1374  	}
  1375  	prefix := gccgoToSymbol(*gccgoprefix)
  1376  	if prefix == "" {
  1377  		prefix = "go"
  1378  	}
  1379  	return prefix + "." + p.PackageName
  1380  }
  1381  
  1382  // Call a function for each entry in an ast.FieldList, passing the
  1383  // index into the list, the name if any, and the type.
  1384  func forFieldList(fl *ast.FieldList, fn func(int, string, ast.Expr)) {
  1385  	if fl == nil {
  1386  		return
  1387  	}
  1388  	i := 0
  1389  	for _, r := range fl.List {
  1390  		if r.Names == nil {
  1391  			fn(i, "", r.Type)
  1392  			i++
  1393  		} else {
  1394  			for _, n := range r.Names {
  1395  				fn(i, n.Name, r.Type)
  1396  				i++
  1397  			}
  1398  		}
  1399  	}
  1400  }
  1401  
  1402  func c(repr string, args ...interface{}) *TypeRepr {
  1403  	return &TypeRepr{repr, args}
  1404  }
  1405  
  1406  // Map predeclared Go types to Type.
  1407  var goTypes = map[string]*Type{
  1408  	"bool":       {Size: 1, Align: 1, C: c("GoUint8")},
  1409  	"byte":       {Size: 1, Align: 1, C: c("GoUint8")},
  1410  	"int":        {Size: 0, Align: 0, C: c("GoInt")},
  1411  	"uint":       {Size: 0, Align: 0, C: c("GoUint")},
  1412  	"rune":       {Size: 4, Align: 4, C: c("GoInt32")},
  1413  	"int8":       {Size: 1, Align: 1, C: c("GoInt8")},
  1414  	"uint8":      {Size: 1, Align: 1, C: c("GoUint8")},
  1415  	"int16":      {Size: 2, Align: 2, C: c("GoInt16")},
  1416  	"uint16":     {Size: 2, Align: 2, C: c("GoUint16")},
  1417  	"int32":      {Size: 4, Align: 4, C: c("GoInt32")},
  1418  	"uint32":     {Size: 4, Align: 4, C: c("GoUint32")},
  1419  	"int64":      {Size: 8, Align: 8, C: c("GoInt64")},
  1420  	"uint64":     {Size: 8, Align: 8, C: c("GoUint64")},
  1421  	"float32":    {Size: 4, Align: 4, C: c("GoFloat32")},
  1422  	"float64":    {Size: 8, Align: 8, C: c("GoFloat64")},
  1423  	"complex64":  {Size: 8, Align: 4, C: c("GoComplex64")},
  1424  	"complex128": {Size: 16, Align: 8, C: c("GoComplex128")},
  1425  }
  1426  
  1427  // Map an ast type to a Type.
  1428  func (p *Package) cgoType(e ast.Expr) *Type {
  1429  	return p.doCgoType(e, make(map[ast.Expr]bool))
  1430  }
  1431  
  1432  // Map an ast type to a Type, avoiding cycles.
  1433  func (p *Package) doCgoType(e ast.Expr, m map[ast.Expr]bool) *Type {
  1434  	if m[e] {
  1435  		fatalf("%s: invalid recursive type", fset.Position(e.Pos()))
  1436  	}
  1437  	m[e] = true
  1438  	switch t := e.(type) {
  1439  	case *ast.StarExpr:
  1440  		x := p.doCgoType(t.X, m)
  1441  		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("%s*", x.C)}
  1442  	case *ast.ArrayType:
  1443  		if t.Len == nil {
  1444  			// Slice: pointer, len, cap.
  1445  			return &Type{Size: p.PtrSize * 3, Align: p.PtrSize, C: c("GoSlice")}
  1446  		}
  1447  		// Non-slice array types are not supported.
  1448  	case *ast.StructType:
  1449  		// Not supported.
  1450  	case *ast.FuncType:
  1451  		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("void*")}
  1452  	case *ast.InterfaceType:
  1453  		return &Type{Size: 2 * p.PtrSize, Align: p.PtrSize, C: c("GoInterface")}
  1454  	case *ast.MapType:
  1455  		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("GoMap")}
  1456  	case *ast.ChanType:
  1457  		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("GoChan")}
  1458  	case *ast.Ident:
  1459  		goTypesFixup := func(r *Type) *Type {
  1460  			if r.Size == 0 { // int or uint
  1461  				rr := new(Type)
  1462  				*rr = *r
  1463  				rr.Size = p.IntSize
  1464  				rr.Align = p.IntSize
  1465  				r = rr
  1466  			}
  1467  			if r.Align > p.PtrSize {
  1468  				r.Align = p.PtrSize
  1469  			}
  1470  			return r
  1471  		}
  1472  		// Look up the type in the top level declarations.
  1473  		// TODO: Handle types defined within a function.
  1474  		for _, d := range p.Decl {
  1475  			gd, ok := d.(*ast.GenDecl)
  1476  			if !ok || gd.Tok != token.TYPE {
  1477  				continue
  1478  			}
  1479  			for _, spec := range gd.Specs {
  1480  				ts, ok := spec.(*ast.TypeSpec)
  1481  				if !ok {
  1482  					continue
  1483  				}
  1484  				if ts.Name.Name == t.Name {
  1485  					// Give a better error than the one
  1486  					// above if we detect a recursive type.
  1487  					if m[ts.Type] {
  1488  						fatalf("%s: invalid recursive type: %s refers to itself", fset.Position(e.Pos()), t.Name)
  1489  					}
  1490  					return p.doCgoType(ts.Type, m)
  1491  				}
  1492  			}
  1493  		}
  1494  		if def := typedef[t.Name]; def != nil {
  1495  			if defgo, ok := def.Go.(*ast.Ident); ok {
  1496  				switch defgo.Name {
  1497  				case "complex64", "complex128":
  1498  					// MSVC does not support the _Complex keyword
  1499  					// nor the complex macro.
  1500  					// Use GoComplex64 and GoComplex128 instead,
  1501  					// which are typedef-ed to a compatible type.
  1502  					// See go.dev/issues/36233.
  1503  					return goTypesFixup(goTypes[defgo.Name])
  1504  				}
  1505  			}
  1506  			return def
  1507  		}
  1508  		if t.Name == "uintptr" {
  1509  			return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("GoUintptr")}
  1510  		}
  1511  		if t.Name == "string" {
  1512  			// The string data is 1 pointer + 1 (pointer-sized) int.
  1513  			return &Type{Size: 2 * p.PtrSize, Align: p.PtrSize, C: c("GoString")}
  1514  		}
  1515  		if t.Name == "error" {
  1516  			return &Type{Size: 2 * p.PtrSize, Align: p.PtrSize, C: c("GoInterface")}
  1517  		}
  1518  		if r, ok := goTypes[t.Name]; ok {
  1519  			return goTypesFixup(r)
  1520  		}
  1521  		error_(e.Pos(), "unrecognized Go type %s", t.Name)
  1522  		return &Type{Size: 4, Align: 4, C: c("int")}
  1523  	case *ast.SelectorExpr:
  1524  		id, ok := t.X.(*ast.Ident)
  1525  		if ok && id.Name == "unsafe" && t.Sel.Name == "Pointer" {
  1526  			return &Type{Size: p.PtrSize, Align: p.PtrSize, C: c("void*")}
  1527  		}
  1528  	}
  1529  	error_(e.Pos(), "Go type not supported in export: %s", gofmt(e))
  1530  	return &Type{Size: 4, Align: 4, C: c("int")}
  1531  }
  1532  
  1533  const gccProlog = `
  1534  #line 1 "cgo-gcc-prolog"
  1535  /*
  1536    If x and y are not equal, the type will be invalid
  1537    (have a negative array count) and an inscrutable error will come
  1538    out of the compiler and hopefully mention "name".
  1539  */
  1540  #define __cgo_compile_assert_eq(x, y, name) typedef char name[(x-y)*(x-y)*-2UL+1UL];
  1541  
  1542  /* Check at compile time that the sizes we use match our expectations. */
  1543  #define __cgo_size_assert(t, n) __cgo_compile_assert_eq(sizeof(t), (size_t)n, _cgo_sizeof_##t##_is_not_##n)
  1544  
  1545  __cgo_size_assert(char, 1)
  1546  __cgo_size_assert(short, 2)
  1547  __cgo_size_assert(int, 4)
  1548  typedef long long __cgo_long_long;
  1549  __cgo_size_assert(__cgo_long_long, 8)
  1550  __cgo_size_assert(float, 4)
  1551  __cgo_size_assert(double, 8)
  1552  
  1553  extern char* _cgo_topofstack(void);
  1554  
  1555  /*
  1556    We use packed structs, but they are always aligned.
  1557    The pragmas and address-of-packed-member are only recognized as warning
  1558    groups in clang 4.0+, so ignore unknown pragmas first.
  1559  */
  1560  #pragma GCC diagnostic ignored "-Wunknown-pragmas"
  1561  #pragma GCC diagnostic ignored "-Wpragmas"
  1562  #pragma GCC diagnostic ignored "-Waddress-of-packed-member"
  1563  #pragma GCC diagnostic ignored "-Wunknown-warning-option"
  1564  #pragma GCC diagnostic ignored "-Wunaligned-access"
  1565  
  1566  #include <errno.h>
  1567  #include <string.h>
  1568  `
  1569  
  1570  // Prologue defining TSAN functions in C.
  1571  const noTsanProlog = `
  1572  #define CGO_NO_SANITIZE_THREAD
  1573  #define _cgo_tsan_acquire()
  1574  #define _cgo_tsan_release()
  1575  `
  1576  
  1577  // This must match the TSAN code in runtime/cgo/libcgo.h.
  1578  // This is used when the code is built with the C/C++ Thread SANitizer,
  1579  // which is not the same as the Go race detector.
  1580  // __tsan_acquire tells TSAN that we are acquiring a lock on a variable,
  1581  // in this case _cgo_sync. __tsan_release releases the lock.
  1582  // (There is no actual lock, we are just telling TSAN that there is.)
  1583  //
  1584  // When we call from Go to C we call _cgo_tsan_acquire.
  1585  // When the C function returns we call _cgo_tsan_release.
  1586  // Similarly, when C calls back into Go we call _cgo_tsan_release
  1587  // and then call _cgo_tsan_acquire when we return to C.
  1588  // These calls tell TSAN that there is a serialization point at the C call.
  1589  //
  1590  // This is necessary because TSAN, which is a C/C++ tool, can not see
  1591  // the synchronization in the Go code. Without these calls, when
  1592  // multiple goroutines call into C code, TSAN does not understand
  1593  // that the calls are properly synchronized on the Go side.
  1594  //
  1595  // To be clear, if the calls are not properly synchronized on the Go side,
  1596  // we will be hiding races. But when using TSAN on mixed Go C/C++ code
  1597  // it is more important to avoid false positives, which reduce confidence
  1598  // in the tool, than to avoid false negatives.
  1599  const yesTsanProlog = `
  1600  #line 1 "cgo-tsan-prolog"
  1601  #define CGO_NO_SANITIZE_THREAD __attribute__ ((no_sanitize_thread))
  1602  
  1603  long long _cgo_sync __attribute__ ((common));
  1604  
  1605  extern void __tsan_acquire(void*);
  1606  extern void __tsan_release(void*);
  1607  
  1608  __attribute__ ((unused))
  1609  static void _cgo_tsan_acquire() {
  1610  	__tsan_acquire(&_cgo_sync);
  1611  }
  1612  
  1613  __attribute__ ((unused))
  1614  static void _cgo_tsan_release() {
  1615  	__tsan_release(&_cgo_sync);
  1616  }
  1617  `
  1618  
  1619  // Set to yesTsanProlog if we see -fsanitize=thread in the flags for gcc.
  1620  var tsanProlog = noTsanProlog
  1621  
  1622  // noMsanProlog is a prologue defining an MSAN function in C.
  1623  // This is used when not compiling with -fsanitize=memory.
  1624  const noMsanProlog = `
  1625  #define _cgo_msan_write(addr, sz)
  1626  `
  1627  
  1628  // yesMsanProlog is a prologue defining an MSAN function in C.
  1629  // This is used when compiling with -fsanitize=memory.
  1630  // See the comment above where _cgo_msan_write is called.
  1631  const yesMsanProlog = `
  1632  extern void __msan_unpoison(const volatile void *, size_t);
  1633  
  1634  #define _cgo_msan_write(addr, sz) __msan_unpoison((addr), (sz))
  1635  `
  1636  
  1637  // msanProlog is set to yesMsanProlog if we see -fsanitize=memory in the flags
  1638  // for the C compiler.
  1639  var msanProlog = noMsanProlog
  1640  
  1641  const builtinProlog = `
  1642  #line 1 "cgo-builtin-prolog"
  1643  #include <stddef.h>
  1644  
  1645  /* Define intgo when compiling with GCC.  */
  1646  typedef ptrdiff_t intgo;
  1647  
  1648  #define GO_CGO_GOSTRING_TYPEDEF
  1649  typedef struct { const char *p; intgo n; } _GoString_;
  1650  typedef struct { char *p; intgo n; intgo c; } _GoBytes_;
  1651  _GoString_ GoString(char *p);
  1652  _GoString_ GoStringN(char *p, int l);
  1653  _GoBytes_ GoBytes(void *p, int n);
  1654  char *CString(_GoString_);
  1655  void *CBytes(_GoBytes_);
  1656  void *_CMalloc(size_t);
  1657  
  1658  __attribute__ ((unused))
  1659  static size_t _GoStringLen(_GoString_ s) { return (size_t)s.n; }
  1660  
  1661  __attribute__ ((unused))
  1662  static const char *_GoStringPtr(_GoString_ s) { return s.p; }
  1663  `
  1664  
  1665  const goProlog = `
  1666  //go:linkname _cgo_runtime_cgocall runtime.cgocall
  1667  func _cgo_runtime_cgocall(unsafe.Pointer, uintptr) int32
  1668  
  1669  //go:linkname _cgoCheckPointer runtime.cgoCheckPointer
  1670  //go:noescape
  1671  func _cgoCheckPointer(interface{}, interface{})
  1672  
  1673  //go:linkname _cgoCheckResult runtime.cgoCheckResult
  1674  //go:noescape
  1675  func _cgoCheckResult(interface{})
  1676  `
  1677  
  1678  const gccgoGoProlog = `
  1679  func _cgoCheckPointer(interface{}, interface{})
  1680  
  1681  func _cgoCheckResult(interface{})
  1682  `
  1683  
  1684  const goStringDef = `
  1685  //go:linkname _cgo_runtime_gostring runtime.gostring
  1686  func _cgo_runtime_gostring(*_Ctype_char) string
  1687  
  1688  // GoString converts the C string p into a Go string.
  1689  func _Cfunc_GoString(p *_Ctype_char) string {
  1690  	return _cgo_runtime_gostring(p)
  1691  }
  1692  `
  1693  
  1694  const goStringNDef = `
  1695  //go:linkname _cgo_runtime_gostringn runtime.gostringn
  1696  func _cgo_runtime_gostringn(*_Ctype_char, int) string
  1697  
  1698  // GoStringN converts the C data p with explicit length l to a Go string.
  1699  func _Cfunc_GoStringN(p *_Ctype_char, l _Ctype_int) string {
  1700  	return _cgo_runtime_gostringn(p, int(l))
  1701  }
  1702  `
  1703  
  1704  const goBytesDef = `
  1705  //go:linkname _cgo_runtime_gobytes runtime.gobytes
  1706  func _cgo_runtime_gobytes(unsafe.Pointer, int) []byte
  1707  
  1708  // GoBytes converts the C data p with explicit length l to a Go []byte.
  1709  func _Cfunc_GoBytes(p unsafe.Pointer, l _Ctype_int) []byte {
  1710  	return _cgo_runtime_gobytes(p, int(l))
  1711  }
  1712  `
  1713  
  1714  const cStringDef = `
  1715  // CString converts the Go string s to a C string.
  1716  //
  1717  // The C string is allocated in the C heap using malloc.
  1718  // It is the caller's responsibility to arrange for it to be
  1719  // freed, such as by calling C.free (be sure to include stdlib.h
  1720  // if C.free is needed).
  1721  func _Cfunc_CString(s string) *_Ctype_char {
  1722  	if len(s)+1 <= 0 {
  1723  		panic("string too large")
  1724  	}
  1725  	p := _cgo_cmalloc(uint64(len(s)+1))
  1726  	sliceHeader := struct {
  1727  		p   unsafe.Pointer
  1728  		len int
  1729  		cap int
  1730  	}{p, len(s)+1, len(s)+1}
  1731  	b := *(*[]byte)(unsafe.Pointer(&sliceHeader))
  1732  	copy(b, s)
  1733  	b[len(s)] = 0
  1734  	return (*_Ctype_char)(p)
  1735  }
  1736  `
  1737  
  1738  const cBytesDef = `
  1739  // CBytes converts the Go []byte slice b to a C array.
  1740  //
  1741  // The C array is allocated in the C heap using malloc.
  1742  // It is the caller's responsibility to arrange for it to be
  1743  // freed, such as by calling C.free (be sure to include stdlib.h
  1744  // if C.free is needed).
  1745  func _Cfunc_CBytes(b []byte) unsafe.Pointer {
  1746  	p := _cgo_cmalloc(uint64(len(b)))
  1747  	sliceHeader := struct {
  1748  		p   unsafe.Pointer
  1749  		len int
  1750  		cap int
  1751  	}{p, len(b), len(b)}
  1752  	s := *(*[]byte)(unsafe.Pointer(&sliceHeader))
  1753  	copy(s, b)
  1754  	return p
  1755  }
  1756  `
  1757  
  1758  const cMallocDef = `
  1759  func _Cfunc__CMalloc(n _Ctype_size_t) unsafe.Pointer {
  1760  	return _cgo_cmalloc(uint64(n))
  1761  }
  1762  `
  1763  
  1764  var builtinDefs = map[string]string{
  1765  	"GoString":  goStringDef,
  1766  	"GoStringN": goStringNDef,
  1767  	"GoBytes":   goBytesDef,
  1768  	"CString":   cStringDef,
  1769  	"CBytes":    cBytesDef,
  1770  	"_CMalloc":  cMallocDef,
  1771  }
  1772  
  1773  // Definitions for C.malloc in Go and in C. We define it ourselves
  1774  // since we call it from functions we define, such as C.CString.
  1775  // Also, we have historically ensured that C.malloc does not return
  1776  // nil even for an allocation of 0.
  1777  
  1778  const cMallocDefGo = `
  1779  //go:cgo_import_static _cgoPREFIX_Cfunc__Cmalloc
  1780  //go:linkname __cgofn__cgoPREFIX_Cfunc__Cmalloc _cgoPREFIX_Cfunc__Cmalloc
  1781  var __cgofn__cgoPREFIX_Cfunc__Cmalloc byte
  1782  var _cgoPREFIX_Cfunc__Cmalloc = unsafe.Pointer(&__cgofn__cgoPREFIX_Cfunc__Cmalloc)
  1783  
  1784  //go:linkname runtime_throw runtime.throw
  1785  func runtime_throw(string)
  1786  
  1787  //go:cgo_unsafe_args
  1788  func _cgo_cmalloc(p0 uint64) (r1 unsafe.Pointer) {
  1789  	_cgo_runtime_cgocall(_cgoPREFIX_Cfunc__Cmalloc, uintptr(unsafe.Pointer(&p0)))
  1790  	if r1 == nil {
  1791  		runtime_throw("runtime: C malloc failed")
  1792  	}
  1793  	return
  1794  }
  1795  `
  1796  
  1797  // cMallocDefC defines the C version of C.malloc for the gc compiler.
  1798  // It is defined here because C.CString and friends need a definition.
  1799  // We define it by hand, rather than simply inventing a reference to
  1800  // C.malloc, because <stdlib.h> may not have been included.
  1801  // This is approximately what writeOutputFunc would generate, but
  1802  // skips the cgo_topofstack code (which is only needed if the C code
  1803  // calls back into Go). This also avoids returning nil for an
  1804  // allocation of 0 bytes.
  1805  const cMallocDefC = `
  1806  CGO_NO_SANITIZE_THREAD
  1807  void _cgoPREFIX_Cfunc__Cmalloc(void *v) {
  1808  	struct {
  1809  		unsigned long long p0;
  1810  		void *r1;
  1811  	} PACKED *a = v;
  1812  	void *ret;
  1813  	_cgo_tsan_acquire();
  1814  	ret = malloc(a->p0);
  1815  	if (ret == 0 && a->p0 == 0) {
  1816  		ret = malloc(1);
  1817  	}
  1818  	a->r1 = ret;
  1819  	_cgo_tsan_release();
  1820  }
  1821  `
  1822  
  1823  func (p *Package) cPrologGccgo() string {
  1824  	r := strings.NewReplacer(
  1825  		"PREFIX", cPrefix,
  1826  		"GCCGOSYMBOLPREF", p.gccgoSymbolPrefix(),
  1827  		"_cgoCheckPointer", gccgoToSymbol("_cgoCheckPointer"),
  1828  		"_cgoCheckResult", gccgoToSymbol("_cgoCheckResult"))
  1829  	return r.Replace(cPrologGccgo)
  1830  }
  1831  
  1832  const cPrologGccgo = `
  1833  #line 1 "cgo-c-prolog-gccgo"
  1834  #include <stdint.h>
  1835  #include <stdlib.h>
  1836  #include <string.h>
  1837  
  1838  typedef unsigned char byte;
  1839  typedef intptr_t intgo;
  1840  
  1841  struct __go_string {
  1842  	const unsigned char *__data;
  1843  	intgo __length;
  1844  };
  1845  
  1846  typedef struct __go_open_array {
  1847  	void* __values;
  1848  	intgo __count;
  1849  	intgo __capacity;
  1850  } Slice;
  1851  
  1852  struct __go_string __go_byte_array_to_string(const void* p, intgo len);
  1853  struct __go_open_array __go_string_to_byte_array (struct __go_string str);
  1854  
  1855  extern void runtime_throw(const char *);
  1856  
  1857  const char *_cgoPREFIX_Cfunc_CString(struct __go_string s) {
  1858  	char *p = malloc(s.__length+1);
  1859  	if(p == NULL)
  1860  		runtime_throw("runtime: C malloc failed");
  1861  	memmove(p, s.__data, s.__length);
  1862  	p[s.__length] = 0;
  1863  	return p;
  1864  }
  1865  
  1866  void *_cgoPREFIX_Cfunc_CBytes(struct __go_open_array b) {
  1867  	char *p = malloc(b.__count);
  1868  	if(p == NULL)
  1869  		runtime_throw("runtime: C malloc failed");
  1870  	memmove(p, b.__values, b.__count);
  1871  	return p;
  1872  }
  1873  
  1874  struct __go_string _cgoPREFIX_Cfunc_GoString(char *p) {
  1875  	intgo len = (p != NULL) ? strlen(p) : 0;
  1876  	return __go_byte_array_to_string(p, len);
  1877  }
  1878  
  1879  struct __go_string _cgoPREFIX_Cfunc_GoStringN(char *p, int32_t n) {
  1880  	return __go_byte_array_to_string(p, n);
  1881  }
  1882  
  1883  Slice _cgoPREFIX_Cfunc_GoBytes(char *p, int32_t n) {
  1884  	struct __go_string s = { (const unsigned char *)p, n };
  1885  	return __go_string_to_byte_array(s);
  1886  }
  1887  
  1888  void *_cgoPREFIX_Cfunc__CMalloc(size_t n) {
  1889  	void *p = malloc(n);
  1890  	if(p == NULL && n == 0)
  1891  		p = malloc(1);
  1892  	if(p == NULL)
  1893  		runtime_throw("runtime: C malloc failed");
  1894  	return p;
  1895  }
  1896  
  1897  struct __go_type_descriptor;
  1898  typedef struct __go_empty_interface {
  1899  	const struct __go_type_descriptor *__type_descriptor;
  1900  	void *__object;
  1901  } Eface;
  1902  
  1903  extern void runtimeCgoCheckPointer(Eface, Eface)
  1904  	__asm__("runtime.cgoCheckPointer")
  1905  	__attribute__((weak));
  1906  
  1907  extern void localCgoCheckPointer(Eface, Eface)
  1908  	__asm__("GCCGOSYMBOLPREF._cgoCheckPointer");
  1909  
  1910  void localCgoCheckPointer(Eface ptr, Eface arg) {
  1911  	if(runtimeCgoCheckPointer) {
  1912  		runtimeCgoCheckPointer(ptr, arg);
  1913  	}
  1914  }
  1915  
  1916  extern void runtimeCgoCheckResult(Eface)
  1917  	__asm__("runtime.cgoCheckResult")
  1918  	__attribute__((weak));
  1919  
  1920  extern void localCgoCheckResult(Eface)
  1921  	__asm__("GCCGOSYMBOLPREF._cgoCheckResult");
  1922  
  1923  void localCgoCheckResult(Eface val) {
  1924  	if(runtimeCgoCheckResult) {
  1925  		runtimeCgoCheckResult(val);
  1926  	}
  1927  }
  1928  `
  1929  
  1930  // builtinExportProlog is a shorter version of builtinProlog,
  1931  // to be put into the _cgo_export.h file.
  1932  // For historical reasons we can't use builtinProlog in _cgo_export.h,
  1933  // because _cgo_export.h defines GoString as a struct while builtinProlog
  1934  // defines it as a function. We don't change this to avoid unnecessarily
  1935  // breaking existing code.
  1936  // The test of GO_CGO_GOSTRING_TYPEDEF avoids a duplicate definition
  1937  // error if a Go file with a cgo comment #include's the export header
  1938  // generated by a different package.
  1939  const builtinExportProlog = `
  1940  #line 1 "cgo-builtin-export-prolog"
  1941  
  1942  #include <stddef.h>
  1943  
  1944  #ifndef GO_CGO_EXPORT_PROLOGUE_H
  1945  #define GO_CGO_EXPORT_PROLOGUE_H
  1946  
  1947  #ifndef GO_CGO_GOSTRING_TYPEDEF
  1948  typedef struct { const char *p; ptrdiff_t n; } _GoString_;
  1949  extern size_t _GoStringLen(_GoString_ s);
  1950  extern const char *_GoStringPtr(_GoString_ s);
  1951  #endif
  1952  
  1953  #endif
  1954  `
  1955  
  1956  func (p *Package) gccExportHeaderProlog() string {
  1957  	return strings.Replace(gccExportHeaderProlog, "GOINTBITS", fmt.Sprint(8*p.IntSize), -1)
  1958  }
  1959  
  1960  // gccExportHeaderProlog is written to the exported header, after the
  1961  // import "C" comment preamble but before the generated declarations
  1962  // of exported functions. This permits the generated declarations to
  1963  // use the type names that appear in goTypes, above.
  1964  //
  1965  // The test of GO_CGO_GOSTRING_TYPEDEF avoids a duplicate definition
  1966  // error if a Go file with a cgo comment #include's the export header
  1967  // generated by a different package. Unfortunately GoString means two
  1968  // different things: in this prolog it means a C name for the Go type,
  1969  // while in the prolog written into the start of the C code generated
  1970  // from a cgo-using Go file it means the C.GoString function. There is
  1971  // no way to resolve this conflict, but it also doesn't make much
  1972  // difference, as Go code never wants to refer to the latter meaning.
  1973  const gccExportHeaderProlog = `
  1974  /* Start of boilerplate cgo prologue.  */
  1975  #line 1 "cgo-gcc-export-header-prolog"
  1976  
  1977  #ifndef GO_CGO_PROLOGUE_H
  1978  #define GO_CGO_PROLOGUE_H
  1979  
  1980  typedef signed char GoInt8;
  1981  typedef unsigned char GoUint8;
  1982  typedef short GoInt16;
  1983  typedef unsigned short GoUint16;
  1984  typedef int GoInt32;
  1985  typedef unsigned int GoUint32;
  1986  typedef long long GoInt64;
  1987  typedef unsigned long long GoUint64;
  1988  typedef GoIntGOINTBITS GoInt;
  1989  typedef GoUintGOINTBITS GoUint;
  1990  typedef size_t GoUintptr;
  1991  typedef float GoFloat32;
  1992  typedef double GoFloat64;
  1993  #ifdef _MSC_VER
  1994  #if !defined(__cplusplus) || _MSVC_LANG <= 201402L
  1995  #include <complex.h>
  1996  typedef _Fcomplex GoComplex64;
  1997  typedef _Dcomplex GoComplex128;
  1998  #else
  1999  #include <complex>
  2000  typedef std::complex<float> GoComplex64;
  2001  typedef std::complex<double> GoComplex128;
  2002  #endif
  2003  #else
  2004  typedef float _Complex GoComplex64;
  2005  typedef double _Complex GoComplex128;
  2006  #endif
  2007  
  2008  /*
  2009    static assertion to make sure the file is being used on architecture
  2010    at least with matching size of GoInt.
  2011  */
  2012  typedef char _check_for_GOINTBITS_bit_pointer_matching_GoInt[sizeof(void*)==GOINTBITS/8 ? 1:-1];
  2013  
  2014  #ifndef GO_CGO_GOSTRING_TYPEDEF
  2015  typedef _GoString_ GoString;
  2016  #endif
  2017  typedef void *GoMap;
  2018  typedef void *GoChan;
  2019  typedef struct { void *t; void *v; } GoInterface;
  2020  typedef struct { void *data; GoInt len; GoInt cap; } GoSlice;
  2021  
  2022  #endif
  2023  
  2024  /* End of boilerplate cgo prologue.  */
  2025  
  2026  #ifdef __cplusplus
  2027  extern "C" {
  2028  #endif
  2029  `
  2030  
  2031  // gccExportHeaderEpilog goes at the end of the generated header file.
  2032  const gccExportHeaderEpilog = `
  2033  #ifdef __cplusplus
  2034  }
  2035  #endif
  2036  `
  2037  
  2038  // gccgoExportFileProlog is written to the _cgo_export.c file when
  2039  // using gccgo.
  2040  // We use weak declarations, and test the addresses, so that this code
  2041  // works with older versions of gccgo.
  2042  const gccgoExportFileProlog = `
  2043  #line 1 "cgo-gccgo-export-file-prolog"
  2044  extern _Bool runtime_iscgo __attribute__ ((weak));
  2045  
  2046  static void GoInit(void) __attribute__ ((constructor));
  2047  static void GoInit(void) {
  2048  	if(&runtime_iscgo)
  2049  		runtime_iscgo = 1;
  2050  }
  2051  
  2052  extern size_t _cgo_wait_runtime_init_done(void) __attribute__ ((weak));
  2053  `
  2054  

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