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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")
)
func badfLine(f *File, line int, format string, args ...interface{}) {
msg := fmt.Sprintf(format, args...)
fmt.Fprintf(os.Stderr, "%s:%d: %s\n", f.name, line, msg)
setExit(1)
}
// checkBuildTag checks that build tags are in the correct location and well-formed.
func checkBuildTag(f *File) {
if !vet("buildtags") {
return
}
// we must look at the raw lines, as build tags may appear in non-Go
// files such as assembly files.
lines := bytes.SplitAfter(f.content, nl)
// lineWithComment reports whether a line corresponds to a comment in
// the source file. If the source file wasn't Go, the function always
// returns true.
lineWithComment := func(line int) bool {
if f.file == nil {
// Current source file is not Go, so be conservative.
return true
}
for _, group := range f.file.Comments {
startLine := f.fset.Position(group.Pos()).Line
endLine := f.fset.Position(group.End()).Line
if startLine <= line && line <= endLine {
return true
}
}
return false
}
// Determine cutpoint where +build comments are no longer valid.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
}
if !bytes.Contains(line, plusBuild) {
// Check that the comment contains "+build" early, to
// avoid unnecessary lineWithComment calls that may
// incur linear searches.
continue
}
if !lineWithComment(i + 1) {
// This is a line in a Go source file that looks like a
// comment, but actually isn't - such as part of a raw
// string.
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.
badfLine(f, i+1, "possible malformed +build comment")
continue
}
if i >= cutoff {
badfLine(f, i+1, "+build comment must appear before package clause and be followed by a blank line")
continue
}
// Check arguments.
Args:
for _, arg := range fields[1:] {
for _, elem := range strings.Split(string(arg), ",") {
if strings.HasPrefix(elem, "!!") {
badfLine(f, i+1, "invalid double negative in build constraint: %s", arg)
break Args
}
elem = strings.TrimPrefix(elem, "!")
for _, c := range elem {
if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' {
badfLine(f, i+1, "invalid non-alphanumeric build constraint: %s", arg)
break Args
}
}
}
}
continue
}
// Comment with +build but not at beginning.
if i < cutoff {
badfLine(f, i+1, "possible malformed +build comment")
continue
}
}
}
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