github.com/d4l3k/go@v0.0.0-20151015000803-65fc379daeda/src/cmd/compile/internal/gc/mkbuiltin.go (about)

     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  // +build ignore
     6  
     7  // Generate builtin.go from $* (runtime.go and unsafe.go).
     8  // Run this after changing runtime.go and unsafe.go
     9  // or after changing the export metadata format in the compiler.
    10  // Either way, you need to have a working compiler binary first.
    11  package main
    12  
    13  import (
    14  	"bufio"
    15  	"fmt"
    16  	"io"
    17  	"log"
    18  	"os"
    19  	"os/exec"
    20  	"strings"
    21  )
    22  
    23  func main() {
    24  	f, err := os.Create("builtin.go")
    25  	if err != nil {
    26  		log.Fatal(err)
    27  	}
    28  	defer f.Close()
    29  	w := bufio.NewWriter(f)
    30  
    31  	fmt.Fprintln(w, "// AUTO-GENERATED by mkbuiltin.go; DO NOT EDIT")
    32  	fmt.Fprintln(w, "")
    33  	fmt.Fprintln(w, "package gc")
    34  
    35  	for _, name := range os.Args[1:] {
    36  		mkbuiltin(w, name)
    37  	}
    38  
    39  	if err := w.Flush(); err != nil {
    40  		log.Fatal(err)
    41  	}
    42  }
    43  
    44  // Compile .go file, import data from .6 file, and write Go string version.
    45  func mkbuiltin(w io.Writer, name string) {
    46  	if err := exec.Command("go", "tool", "compile", "-A", "builtin/"+name+".go").Run(); err != nil {
    47  		log.Fatal(err)
    48  	}
    49  	obj := name + ".o"
    50  	defer os.Remove(obj)
    51  
    52  	r, err := os.Open(obj)
    53  	if err != nil {
    54  		log.Fatal(err)
    55  	}
    56  	defer r.Close()
    57  	scanner := bufio.NewScanner(r)
    58  
    59  	// Look for $$ that introduces imports.
    60  	for scanner.Scan() {
    61  		if strings.Contains(scanner.Text(), "$$") {
    62  			goto Begin
    63  		}
    64  	}
    65  	log.Fatal("did not find beginning of imports")
    66  
    67  Begin:
    68  	initfunc := fmt.Sprintf("init_%s_function", name)
    69  
    70  	fmt.Fprintf(w, "\nconst %simport = \"\" +\n", name)
    71  
    72  	// sys.go claims to be in package PACKAGE to avoid
    73  	// conflicts during "go tool compile sys.go".  Rename PACKAGE to $2.
    74  	replacer := strings.NewReplacer("PACKAGE", name)
    75  
    76  	// Process imports, stopping at $$ that closes them.
    77  	for scanner.Scan() {
    78  		p := scanner.Text()
    79  		if strings.Contains(p, "$$") {
    80  			goto End
    81  		}
    82  
    83  		// Chop leading white space.
    84  		p = strings.TrimLeft(p, " \t")
    85  
    86  		// Cut out decl of init_$1_function - it doesn't exist.
    87  		if strings.Contains(p, initfunc) {
    88  			continue
    89  		}
    90  
    91  		fmt.Fprintf(w, "\t%q +\n", replacer.Replace(p)+"\n")
    92  	}
    93  	log.Fatal("did not find end of imports")
    94  
    95  End:
    96  	fmt.Fprintf(w, "\t\"$$\\n\"\n")
    97  }