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Source file src/cmd/vet/buildtag.go

Documentation: cmd/vet

     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    28  	// Determine cutpoint where +build comments are no longer valid.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  }
    92  

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