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// Copyright 2013 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 (
"bytes"
"fmt"
"os"
"strings"
"unicode"
)
var (
nl = []byte("\n")
slashSlash = []byte("//")
plusBuild = []byte("+build")
)
// checkBuildTag checks that build tags are in the correct location and well-formed.
func checkBuildTag(name string, data []byte) {
if !vet("buildtags") {
return
}
lines := bytes.SplitAfter(data, nl)
// Determine cutpoint where +build comments are no longer valid.
// They are valid in leading // comments in the file followed by
// a blank line.
var cutoff int
for i, line := range lines {
line = bytes.TrimSpace(line)
if len(line) == 0 {
cutoff = i
continue
}
if bytes.HasPrefix(line, slashSlash) {
continue
}
break
}
for i, line := range lines {
line = bytes.TrimSpace(line)
if !bytes.HasPrefix(line, slashSlash) {
continue
}
text := bytes.TrimSpace(line[2:])
if bytes.HasPrefix(text, plusBuild) {
fields := bytes.Fields(text)
if !bytes.Equal(fields[0], plusBuild) {
// Comment is something like +buildasdf not +build.
fmt.Fprintf(os.Stderr, "%s:%d: possible malformed +build comment\n", name, i+1)
setExit(1)
continue
}
if i >= cutoff {
fmt.Fprintf(os.Stderr, "%s:%d: +build comment must appear before package clause and be followed by a blank line\n", name, i+1)
setExit(1)
continue
}
// Check arguments.
Args:
for _, arg := range fields[1:] {
for _, elem := range strings.Split(string(arg), ",") {
if strings.HasPrefix(elem, "!!") {
fmt.Fprintf(os.Stderr, "%s:%d: invalid double negative in build constraint: %s\n", name, i+1, arg)
setExit(1)
break Args
}
elem = strings.TrimPrefix(elem, "!")
for _, c := range elem {
if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' {
fmt.Fprintf(os.Stderr, "%s:%d: invalid non-alphanumeric build constraint: %s\n", name, i+1, arg)
setExit(1)
break Args
}
}
}
}
continue
}
// Comment with +build but not at beginning.
if bytes.Contains(line, plusBuild) && i < cutoff {
fmt.Fprintf(os.Stderr, "%s:%d: possible malformed +build comment\n", name, i+1)
setExit(1)
continue
}
}
}
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