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Source file src/cmd/vet/buildtag.go

Documentation: cmd/vet

  // 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  	// Determine cutpoint where +build comments are no longer valid.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
  					}
  					if strings.HasPrefix(elem, "!") {
  						elem = elem[1:]
  					}
  					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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