libgo/go/cmd/vet/buildtag.go

   1 // Copyright 2013 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         "fmt"
  10         "os"
  11         "strings"
  12         "unicode"
  13 )
  14
  15 var (
  16         nl         = []byte("\n")
  17         slashSlash = []byte("//")
  18         plusBuild  = []byte("+build")
  19 )
  20
  21 // checkBuildTag checks that build tags are in the correct location and well-formed.
  22 func checkBuildTag(name string, data []byte) {
  23         if !vet("buildtags") {
  24                 return
  25         }
  26         lines := bytes.SplitAfter(data, nl)
  27
  28         // Determine cutpoint where +build comments are no longer valid.
  29         // They are valid in leading // comments in the file followed by
  30         // a blank line.
  31         var cutoff int
  32         for i, line := range lines {
  33                 line = bytes.TrimSpace(line)
  34                 if len(line) == 0 {
  35                         cutoff = i
  36                         continue
  37                 }
  38                 if bytes.HasPrefix(line, slashSlash) {
  39                         continue
  40                 }
  41                 break
  42         }
  43
  44         for i, line := range lines {
  45                 line = bytes.TrimSpace(line)
  46                 if !bytes.HasPrefix(line, slashSlash) {
  47                         continue
  48                 }
  49                 text := bytes.TrimSpace(line[2:])
  50                 if bytes.HasPrefix(text, plusBuild) {
  51                         fields := bytes.Fields(text)
  52                         if !bytes.Equal(fields[0], plusBuild) {
  53                                 // Comment is something like +buildasdf not +build.
  54                                 fmt.Fprintf(os.Stderr, "%s:%d: possible malformed +build comment\n", name, i+1)
  55                                 setExit(1)
  56                                 continue
  57                         }
  58                         if i >= cutoff {
  59                                 fmt.Fprintf(os.Stderr, "%s:%d: +build comment must appear before package clause and be followed by a blank line\n", name, i+1)
  60                                 setExit(1)
  61                                 continue
  62                         }
  63                         // Check arguments.
  64                 Args:
  65                         for _, arg := range fields[1:] {
  66                                 for _, elem := range strings.Split(string(arg), ",") {
  67                                         if strings.HasPrefix(elem, "!!") {
  68                                                 fmt.Fprintf(os.Stderr, "%s:%d: invalid double negative in build constraint: %s\n", name, i+1, arg)
  69                                                 setExit(1)
  70                                                 break Args
  71                                         }
  72                                         elem = strings.TrimPrefix(elem, "!")
  73                                         for _, c := range elem {
  74                                                 if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' {
  75                                                         fmt.Fprintf(os.Stderr, "%s:%d: invalid non-alphanumeric build constraint: %s\n", name, i+1, arg)
  76                                                         setExit(1)
  77                                                         break Args
  78                                                 }
  79                                         }
  80                                 }
  81                         }
  82                         continue
  83                 }
  84                 // Comment with +build but not at beginning.
  85                 if bytes.Contains(line, plusBuild) && i < cutoff {
  86                         fmt.Fprintf(os.Stderr, "%s:%d: possible malformed +build comment\n", name, i+1)
  87                         setExit(1)
  88                         continue
  89                 }
  90         }
  91 }