src/cmd/cgo/out.go

// Copyright 2009 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"fmt"
	"go/ast"
	"go/printer"
	"go/token"
	"os"
	"strings"
)

func creat(name string) *os.File {
	f, err := os.Open(name, os.O_WRONLY|os.O_CREAT|os.O_TRUNC, 0666)
	if err != nil {
		fatal("%s", err)
	}
	return f
}

// writeDefs creates output files to be compiled by 6g, 6c, and gcc.
// (The comments here say 6g and 6c but the code applies to the 8 and 5 tools too.)
func (p *Prog) writeDefs() {
	pkgroot := os.Getenv("GOROOT") + "/pkg/" + os.Getenv("GOOS") + "_" + os.Getenv("GOARCH")
	path := p.PackagePath
	if !strings.HasPrefix(path, "/") {
		path = pkgroot + "/" + path
	}

	fgo2 := creat("_cgo_gotypes.go")
	fc := creat("_cgo_defun.c")

	// Write second Go output: definitions of _C_xxx.
	// In a separate file so that the import of "unsafe" does not
	// pollute the original file.
	fmt.Fprintf(fgo2, "// Created by cgo - DO NOT EDIT\n")
	fmt.Fprintf(fgo2, "package %s\n\n", p.Package)
	fmt.Fprintf(fgo2, "import \"unsafe\"\n\n")
	fmt.Fprintf(fgo2, "type _ unsafe.Pointer\n\n")

	for name, def := range p.Typedef {
		fmt.Fprintf(fgo2, "type %s ", name)
		printer.Fprint(fgo2, def)
		fmt.Fprintf(fgo2, "\n")
	}
	fmt.Fprintf(fgo2, "type _C_void [0]byte\n")

	fmt.Fprintf(fc, cProlog, pkgroot, pkgroot, pkgroot, pkgroot, pkgroot)

	for name, def := range p.Vardef {
		fmt.Fprintf(fc, "#pragma dynimport ·_C_%s %s \"%s.so\"\n", name, name, path)
		fmt.Fprintf(fgo2, "var _C_%s ", name)
		printer.Fprint(fgo2, &ast.StarExpr{X: def.Go})
		fmt.Fprintf(fgo2, "\n")
	}
	fmt.Fprintf(fc, "\n")

	for name, value := range p.Constdef {
		fmt.Fprintf(fgo2, "const %s = %s\n", name, value)
	}

	for name, value := range p.Enumdef {
		fmt.Fprintf(fgo2, "const %s = %d\n", name, value)
	}
	fmt.Fprintf(fgo2, "\n")

	for name, def := range p.Funcdef {
		// Go func declaration.
		d := &ast.FuncDecl{
			Name: ast.NewIdent("_C_" + name),
			Type: def.Go,
		}
		printer.Fprint(fgo2, d)
		fmt.Fprintf(fgo2, "\n")

		if name == "CString" || name == "GoString" {
			// The builtins are already defined in the C prolog.
			continue
		}

		// Construct a gcc struct matching the 6c argument frame.
		// Assumes that in gcc, char is 1 byte, short 2 bytes, int 4 bytes, long long 8 bytes.
		// These assumptions are checked by the gccProlog.
		// Also assumes that 6c convention is to word-align the
		// input and output parameters.
		structType := "struct {\n"
		off := int64(0)
		npad := 0
		for i, t := range def.Params {
			if off%t.Align != 0 {
				pad := t.Align - off%t.Align
				structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
				off += pad
				npad++
			}
			structType += fmt.Sprintf("\t\t%s p%d;\n", t.C, i)
			off += t.Size
		}
		if off%p.PtrSize != 0 {
			pad := p.PtrSize - off%p.PtrSize
			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
			off += pad
			npad++
		}
		if t := def.Result; t != nil {
			if off%t.Align != 0 {
				pad := t.Align - off%t.Align
				structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
				off += pad
				npad++
			}
			structType += fmt.Sprintf("\t\t%s r;\n", t.C)
			off += t.Size
		}
		if off%p.PtrSize != 0 {
			pad := p.PtrSize - off%p.PtrSize
			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
			off += pad
			npad++
		}
		if len(def.Params) == 0 && def.Result == nil {
			structType += "\t\tchar unused;\n" // avoid empty struct
			off++
		}
		structType += "\t}"
		argSize := off

		// C wrapper calls into gcc, passing a pointer to the argument frame.
		// Also emit #pragma to get a pointer to the gcc wrapper.
		fmt.Fprintf(fc, "#pragma dynimport _cgo_%s _cgo_%s \"%s.so\"\n", name, name, path)
		fmt.Fprintf(fc, "void (*_cgo_%s)(void*);\n", name)
		fmt.Fprintf(fc, "\n")
		fmt.Fprintf(fc, "void\n")
		fmt.Fprintf(fc, "·_C_%s(struct{uint8 x[%d];}p)\n", name, argSize)
		fmt.Fprintf(fc, "{\n")
		fmt.Fprintf(fc, "\tcgocall(_cgo_%s, &p);\n", name)
		fmt.Fprintf(fc, "}\n")
		fmt.Fprintf(fc, "\n")
	}

	p.writeExports(fgo2, fc)

	fgo2.Close()
	fc.Close()
}

// writeOutput creates stubs for a specific source file to be compiled by 6g
// (The comments here say 6g and 6c but the code applies to the 8 and 5 tools too.)
func (p *Prog) writeOutput(srcfile string) {
	base := srcfile
	if strings.HasSuffix(base, ".go") {
		base = base[0 : len(base)-3]
	}
	fgo1 := creat(base + ".cgo1.go")
	fgcc := creat(base + ".cgo2.c")

	// Write Go output: Go input with rewrites of C.xxx to _C_xxx.
	fmt.Fprintf(fgo1, "// Created by cgo - DO NOT EDIT\n")
	fmt.Fprintf(fgo1, "//line %s:1\n", srcfile)
	printer.Fprint(fgo1, p.AST)

	// While we process the vars and funcs, also write 6c and gcc output.
	// Gcc output starts with the preamble.
	fmt.Fprintf(fgcc, "%s\n", p.Preamble)
	fmt.Fprintf(fgcc, "%s\n", gccProlog)

	for name, def := range p.Funcdef {
		_, ok := p.OutDefs[name]
		if name == "CString" || name == "GoString" || ok {
			// The builtins are already defined in the C prolog, and we don't
			// want to duplicate function definitions we've already done.
			continue
		}
		p.OutDefs[name] = true

		// Construct a gcc struct matching the 6c argument frame.
		// Assumes that in gcc, char is 1 byte, short 2 bytes, int 4 bytes, long long 8 bytes.
		// These assumptions are checked by the gccProlog.
		// Also assumes that 6c convention is to word-align the
		// input and output parameters.
		structType := "struct {\n"
		off := int64(0)
		npad := 0
		for i, t := range def.Params {
			if off%t.Align != 0 {
				pad := t.Align - off%t.Align
				structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
				off += pad
				npad++
			}
			structType += fmt.Sprintf("\t\t%s p%d;\n", t.C, i)
			off += t.Size
		}
		if off%p.PtrSize != 0 {
			pad := p.PtrSize - off%p.PtrSize
			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
			off += pad
			npad++
		}
		if t := def.Result; t != nil {
			if off%t.Align != 0 {
				pad := t.Align - off%t.Align
				structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
				off += pad
				npad++
			}
			structType += fmt.Sprintf("\t\t%s r;\n", t.C)
			off += t.Size
		}
		if off%p.PtrSize != 0 {
			pad := p.PtrSize - off%p.PtrSize
			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
			off += pad
			npad++
		}
		if len(def.Params) == 0 && def.Result == nil {
			structType += "\t\tchar unused;\n" // avoid empty struct
			off++
		}
		structType += "\t}"

		// Gcc wrapper unpacks the C argument struct
		// and calls the actual C function.
		fmt.Fprintf(fgcc, "void\n")
		fmt.Fprintf(fgcc, "_cgo_%s(void *v)\n", name)
		fmt.Fprintf(fgcc, "{\n")
		fmt.Fprintf(fgcc, "\t%s *a = v;\n", structType)
		fmt.Fprintf(fgcc, "\t")
		if def.Result != nil {
			fmt.Fprintf(fgcc, "a->r = ")
		}
		fmt.Fprintf(fgcc, "%s(", name)
		for i := range def.Params {
			if i > 0 {
				fmt.Fprintf(fgcc, ", ")
			}
			fmt.Fprintf(fgcc, "a->p%d", i)
		}
		fmt.Fprintf(fgcc, ");\n")
		fmt.Fprintf(fgcc, "}\n")
		fmt.Fprintf(fgcc, "\n")
	}

	fgo1.Close()
	fgcc.Close()
}

// Write out the various stubs we need to support functions exported
// from Go so that they are callable from C.
func (p *Prog) writeExports(fgo2, fc *os.File) {
	if len(p.ExpFuncs) == 0 {
		return
	}

	fgcc := creat("_cgo_export.c")
	fgcch := creat("_cgo_export.h")

	fmt.Fprintf(fgcch, "/* Created by cgo - DO NOT EDIT. */\n")
	fmt.Fprintf(fgcch, "%s\n", gccExportHeaderProlog)

	fmt.Fprintf(fgcc, "/* Created by cgo - DO NOT EDIT. */\n")
	fmt.Fprintf(fgcc, "#include \"_cgo_export.h\"\n")

	for _, exp := range p.ExpFuncs {
		fn := exp.Func

		// Construct a gcc struct matching the 6c argument and
		// result frame.
		structType := "struct {\n"
		off := int64(0)
		npad := 0
		if fn.Recv != nil {
			t := p.cgoType(fn.Recv.List[0].Type)
			structType += fmt.Sprintf("\t\t%s recv;\n", t.C)
			off += t.Size
		}
		fntype := fn.Type
		forFieldList(fntype.Params,
			func(i int, atype ast.Expr) {
				t := p.cgoType(atype)
				if off%t.Align != 0 {
					pad := t.Align - off%t.Align
					structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
					off += pad
					npad++
				}
				structType += fmt.Sprintf("\t\t%s p%d;\n", t.C, i)
				off += t.Size
			})
		if off%p.PtrSize != 0 {
			pad := p.PtrSize - off%p.PtrSize
			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
			off += pad
			npad++
		}
		forFieldList(fntype.Results,
			func(i int, atype ast.Expr) {
				t := p.cgoType(atype)
				if off%t.Align != 0 {
					pad := t.Align - off%t.Align
					structType += fmt.Sprintf("\t\tchar __pad%d[%d]\n", npad, pad)
					off += pad
					npad++
				}
				structType += fmt.Sprintf("\t\t%s r%d;\n", t.C, i)
				off += t.Size
			})
		if off%p.PtrSize != 0 {
			pad := p.PtrSize - off%p.PtrSize
			structType += fmt.Sprintf("\t\tchar __pad%d[%d];\n", npad, pad)
			off += pad
			npad++
		}
		if structType == "struct {\n" {
			structType += "\t\tchar unused;\n" // avoid empty struct
			off++
		}
		structType += "\t}"

		// Get the return type of the wrapper function
		// compiled by gcc.
		gccResult := ""
		if fntype.Results == nil || len(fntype.Results.List) == 0 {
			gccResult = "void"
		} else if len(fntype.Results.List) == 1 && len(fntype.Results.List[0].Names) <= 1 {
			gccResult = p.cgoType(fntype.Results.List[0].Type).C
		} else {
			fmt.Fprintf(fgcch, "\n/* Return type for %s */\n", exp.ExpName)
			fmt.Fprintf(fgcch, "struct %s_return {\n", exp.ExpName)
			forFieldList(fntype.Results,
				func(i int, atype ast.Expr) {
					fmt.Fprintf(fgcch, "\t%s r%d;\n", p.cgoType(atype).C, i)
				})
			fmt.Fprintf(fgcch, "};\n")
			gccResult = "struct " + exp.ExpName + "_return"
		}

		// Build the wrapper function compiled by gcc.
		s := fmt.Sprintf("%s %s(", gccResult, exp.ExpName)
		if fn.Recv != nil {
			s += p.cgoType(fn.Recv.List[0].Type).C
			s += " recv"
		}
		forFieldList(fntype.Params,
			func(i int, atype ast.Expr) {
				if i > 0 || fn.Recv != nil {
					s += ", "
				}
				s += fmt.Sprintf("%s p%d", p.cgoType(atype).C, i)
			})
		s += ")"
		fmt.Fprintf(fgcch, "\nextern %s;\n", s)

		fmt.Fprintf(fgcc, "extern _cgoexp_%s(void *, int);\n", exp.ExpName)
		fmt.Fprintf(fgcc, "\n%s\n", s)
		fmt.Fprintf(fgcc, "{\n")
		fmt.Fprintf(fgcc, "\t%s a;\n", structType)
		if gccResult != "void" && (len(fntype.Results.List) > 1 || len(fntype.Results.List[0].Names) > 1) {
			fmt.Fprintf(fgcc, "\t%s r;\n", gccResult)
		}
		if fn.Recv != nil {
			fmt.Fprintf(fgcc, "\ta.recv = recv;\n")
		}
		forFieldList(fntype.Params,
			func(i int, atype ast.Expr) {
				fmt.Fprintf(fgcc, "\ta.p%d = p%d;\n", i, i)
			})
		fmt.Fprintf(fgcc, "\tcrosscall2(_cgoexp_%s, &a, (int) sizeof a);\n", exp.ExpName)
		if gccResult != "void" {
			if len(fntype.Results.List) == 1 && len(fntype.Results.List[0].Names) <= 1 {
				fmt.Fprintf(fgcc, "\treturn a.r0;\n")
			} else {
				forFieldList(fntype.Results,
					func(i int, atype ast.Expr) {
						fmt.Fprintf(fgcc, "\tr.r%d = a.r%d;\n", i, i)
					})
				fmt.Fprintf(fgcc, "\treturn r;\n")
			}
		}
		fmt.Fprintf(fgcc, "}\n")

		// Build the wrapper function compiled by 6c/8c
		goname := exp.Func.Name.Name()
		if fn.Recv != nil {
			goname = "_cgoexpwrap_" + fn.Recv.List[0].Names[0].Name() + "_" + goname
		}
		fmt.Fprintf(fc, "#pragma dynexport _cgoexp_%s _cgoexp_%s\n", exp.ExpName, exp.ExpName)
		fmt.Fprintf(fc, "extern void ·%s();\n", goname)
		fmt.Fprintf(fc, "\nvoid\n")
		fmt.Fprintf(fc, "_cgoexp_%s(void *a, int32 n)\n", exp.ExpName)
		fmt.Fprintf(fc, "{\n")
		fmt.Fprintf(fc, "\tcgocallback(·%s, a, n);\n", goname)
		fmt.Fprintf(fc, "}\n")

		// Calling a function with a receiver from C requires
		// a Go wrapper function.
		if fn.Recv != nil {
			fmt.Fprintf(fgo2, "func %s(recv ", goname)
			printer.Fprint(fgo2, fn.Recv.List[0].Type)
			forFieldList(fntype.Params,
				func(i int, atype ast.Expr) {
					fmt.Fprintf(fgo2, ", p%d", i)
					printer.Fprint(fgo2, atype)
				})
			fmt.Fprintf(fgo2, ")")
			if gccResult != "void" {
				fmt.Fprint(fgo2, " (")
				forFieldList(fntype.Results,
					func(i int, atype ast.Expr) {
						if i > 0 {
							fmt.Fprint(fgo2, ", ")
						}
						printer.Fprint(fgo2, atype)
					})
				fmt.Fprint(fgo2, ")")
			}
			fmt.Fprint(fgo2, " {\n")
			fmt.Fprint(fgo2, "\t")
			if gccResult != "void" {
				fmt.Fprint(fgo2, "return ")
			}
			fmt.Fprintf(fgo2, "recv.%s(", exp.Func.Name)
			forFieldList(fntype.Params,
				func(i int, atype ast.Expr) {
					if i > 0 {
						fmt.Fprint(fgo2, ", ")
					}
					fmt.Fprintf(fgo2, "p%d", i)
				})
			fmt.Fprint(fgo2, ")\n")
			fmt.Fprint(fgo2, "}\n")
		}
	}
}

// Call a function for each entry in an ast.FieldList, passing the
// index into the list and the type.
func forFieldList(fl *ast.FieldList, fn func(int, ast.Expr)) {
	if fl == nil {
		return
	}
	i := 0
	for _, r := range fl.List {
		if r.Names == nil {
			fn(i, r.Type)
			i++
		} else {
			for _ = range r.Names {
				fn(i, r.Type)
				i++
			}
		}
	}
}

// Map predeclared Go types to Type.
var goTypes = map[string]*Type{
	"int":        &Type{Size: 4, Align: 4, C: "int"},
	"uint":       &Type{Size: 4, Align: 4, C: "uint"},
	"int8":       &Type{Size: 1, Align: 1, C: "schar"},
	"uint8":      &Type{Size: 1, Align: 1, C: "uchar"},
	"int16":      &Type{Size: 2, Align: 2, C: "short"},
	"uint16":     &Type{Size: 2, Align: 2, C: "ushort"},
	"int32":      &Type{Size: 4, Align: 4, C: "int"},
	"uint32":     &Type{Size: 4, Align: 4, C: "uint"},
	"int64":      &Type{Size: 8, Align: 8, C: "int64"},
	"uint64":     &Type{Size: 8, Align: 8, C: "uint64"},
	"float":      &Type{Size: 4, Align: 4, C: "float"},
	"float32":    &Type{Size: 4, Align: 4, C: "float"},
	"float64":    &Type{Size: 8, Align: 8, C: "double"},
	"complex":    &Type{Size: 8, Align: 8, C: "__complex float"},
	"complex64":  &Type{Size: 8, Align: 8, C: "__complex float"},
	"complex128": &Type{Size: 16, Align: 16, C: "__complex double"},
}

// Map an ast type to a Type.
func (p *Prog) cgoType(e ast.Expr) *Type {
	switch t := e.(type) {
	case *ast.StarExpr:
		x := p.cgoType(t.X)
		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: x.C + "*"}
	case *ast.ArrayType:
		if t.Len == nil {
			return &Type{Size: p.PtrSize + 8, Align: p.PtrSize, C: "GoSlice"}
		}
	case *ast.StructType:
		// TODO
	case *ast.FuncType:
		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: "void*"}
	case *ast.InterfaceType:
		return &Type{Size: 3 * p.PtrSize, Align: p.PtrSize, C: "GoInterface"}
	case *ast.MapType:
		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: "GoMap"}
	case *ast.ChanType:
		return &Type{Size: p.PtrSize, Align: p.PtrSize, C: "GoChan"}
	case *ast.Ident:
		// Look up the type in the top level declarations.
		// TODO: Handle types defined within a function.
		for _, d := range p.AST.Decls {
			gd, ok := d.(*ast.GenDecl)
			if !ok || gd.Tok != token.TYPE {
				continue
			}
			for _, spec := range gd.Specs {
				ts, ok := spec.(*ast.TypeSpec)
				if !ok {
					continue
				}
				if ts.Name.Name() == t.Name() {
					return p.cgoType(ts.Type)
				}
			}
		}
		for name, def := range p.Typedef {
			if name == t.Name() {
				return p.cgoType(def)
			}
		}
		if t.Name() == "uintptr" {
			return &Type{Size: p.PtrSize, Align: p.PtrSize, C: "uintptr"}
		}
		if t.Name() == "string" {
			return &Type{Size: p.PtrSize + 4, Align: p.PtrSize, C: "GoString"}
		}
		if r, ok := goTypes[t.Name()]; ok {
			if r.Align > p.PtrSize {
				r.Align = p.PtrSize
			}
			return r
		}
	}
	error(e.Pos(), "unrecognized Go type %v", e)
	return &Type{Size: 4, Align: 4, C: "int"}
}

const gccProlog = `
// Usual nonsense: if x and y are not equal, the type will be invalid
// (have a negative array count) and an inscrutable error will come
// out of the compiler and hopefully mention "name".
#define __cgo_compile_assert_eq(x, y, name) typedef char name[(x-y)*(x-y)*-2+1];

// Check at compile time that the sizes we use match our expectations.
#define __cgo_size_assert(t, n) __cgo_compile_assert_eq(sizeof(t), n, _cgo_sizeof_##t##_is_not_##n)

__cgo_size_assert(char, 1)
__cgo_size_assert(short, 2)
__cgo_size_assert(int, 4)
typedef long long __cgo_long_long;
__cgo_size_assert(__cgo_long_long, 8)
__cgo_size_assert(float, 4)
__cgo_size_assert(double, 8)
`

const builtinProlog = `
typedef struct { char *p; int n; } _GoString_;
_GoString_ GoString(char *p);
char *CString(_GoString_);
`

const cProlog = `
#include "runtime.h"
#include "cgocall.h"

#pragma dynimport initcgo initcgo "%s/libcgo.so"
#pragma dynimport libcgo_thread_start libcgo_thread_start "%s/libcgo.so"
#pragma dynimport libcgo_set_scheduler libcgo_set_scheduler "%s/libcgo.so"
#pragma dynimport _cgo_malloc _cgo_malloc "%s/libcgo.so"
#pragma dynimport _cgo_free _cgo_free "%s/libcgo.so"

void
·_C_GoString(int8 *p, String s)
{
	s = gostring((byte*)p);
	FLUSH(&s);
}

void
·_C_CString(String s, int8 *p)
{
	p = cmalloc(s.len+1);
	mcpy((byte*)p, s.str, s.len);
	p[s.len] = 0;
	FLUSH(&p);
}
`

const gccExportHeaderProlog = `
typedef unsigned int uint;
typedef signed char schar;
typedef unsigned char uchar;
typedef unsigned short ushort;
typedef long long int64;
typedef unsigned long long uint64;

typedef struct { char *p; int n; } GoString;
typedef void *GoMap;
typedef void *GoChan;
typedef struct { void *t; void *v; } GoInterface;
`