build-aux/useless-if-before-free

   1 eval '(exit $?0)' && eval 'exec perl -wST "$0" ${1+"$@"}'
   2   & eval 'exec perl -wST "$0" $argv:q'
   3     if 0;
   4 # Detect instances of "if (p) free (p);".
   5 # Likewise for "if (p != NULL) free (p);".  And with braces.
   6 # Also detect "if (NULL != p) free (p);".
   7 # And with 0 in place of NULL.
   8
   9 my $VERSION = '2009-04-16 15:57'; # UTC
  10 # The definition above must lie within the first 8 lines in order
  11 # for the Emacs time-stamp write hook (at end) to update it.
  12 # If you change this file with Emacs, please let the write hook
  13 # do its job.  Otherwise, update this string manually.
  14
  15 # Copyright (C) 2008-2010 Free Software Foundation, Inc.
  16
  17 # This program is free software: you can redistribute it and/or modify
  18 # it under the terms of the GNU General Public License as published by
  19 # the Free Software Foundation, either version 3 of the License, or
  20 # (at your option) any later version.
  21
  22 # This program is distributed in the hope that it will be useful,
  23 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  24 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25 # GNU General Public License for more details.
  26
  27 # You should have received a copy of the GNU General Public License
  28 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  29
  30 # Written by Jim Meyering
  31
  32 use strict;
  33 use warnings;
  34 use Getopt::Long;
  35
  36 (my $ME = $0) =~ s|.*/||;
  37
  38 # use File::Coda; # http://meyering.net/code/Coda/
  39 END {
  40   defined fileno STDOUT or return;
  41   close STDOUT and return;
  42   warn "$ME: failed to close standard output: $!\n";
  43   $? ||= 1;
  44 }
  45
  46 sub usage ($)
  47 {
  48   my ($exit_code) = @_;
  49   my $STREAM = ($exit_code == 0 ? *STDOUT : *STDERR);
  50   if ($exit_code != 0)
  51     {
  52       print $STREAM "Try `$ME --help' for more information.\n";
  53     }
  54   else
  55     {
  56       print $STREAM <<EOF;
  57 Usage: $ME [OPTIONS] FILE...
  58
  59 Detect any instance in FILE of a useless "if" test before a free call, e.g.,
  60 "if (p) free (p);".  Any such test may be safely removed without affecting
  61 the semantics of the C code in FILE.  Use --name=FOO --name=BAR to also
  62 detect free-like functions named FOO and BAR.
  63
  64 OPTIONS:
  65
  66    --list       print only the name of each matching FILE (\0-terminated)
  67    --name=N     add name N to the list of \`free\'-like functions to detect;
  68                   may be repeated
  69
  70    --help       display this help and exit
  71    --version    output version information and exit
  72
  73 Exit status:
  74
  75   0   one or more matches
  76   1   no match
  77   2   an error
  78
  79 EXAMPLE:
  80
  81 For example, this command prints all removable "if" tests before "free"
  82 and "kfree" calls in the linux kernel sources:
  83
  84     git ls-files -z |xargs -0 $ME --name=kfree
  85
  86 EOF
  87     }
  88   exit $exit_code;
  89 }
  90
  91 sub is_NULL ($)
  92 {
  93   my ($expr) = @_;
  94   return ($expr eq 'NULL' || $expr eq '0');
  95 }
  96
  97 {
  98   sub EXIT_MATCH {0}
  99   sub EXIT_NO_MATCH {1}
 100   sub EXIT_ERROR {2}
 101   my $err = EXIT_NO_MATCH;
 102
 103   my $list;
 104   my @name = qw(free);
 105   GetOptions
 106     (
 107      help => sub { usage 0 },
 108      version => sub { print "$ME version $VERSION\n"; exit },
 109      list => \$list,
 110      'name=s@' => \@name,
 111     ) or usage 1;
 112
 113   # Make sure we have the right number of non-option arguments.
 114   # Always tell the user why we fail.
 115   @ARGV < 1
 116     and (warn "$ME: missing FILE argument\n"), usage EXIT_ERROR;
 117
 118   my $or = join '|', @name;
 119   my $regexp = qr/(?:$or)/;
 120
 121   # Set the input record separator.
 122   # Note: this makes it impractical to print line numbers.
 123   $/ = '"';
 124
 125   my $found_match = 0;
 126  FILE:
 127   foreach my $file (@ARGV)
 128     {
 129       open FH, '<', $file
 130         or (warn "$ME: can't open `$file' for reading: $!\n"),
 131           $err = EXIT_ERROR, next;
 132       while (defined (my $line = <FH>))
 133         {
 134           while ($line =~
 135               /\b(if\s*\(\s*([^)]+?)(?:\s*!=\s*([^)]+?))?\s*\)
 136               #  1          2                  3
 137                (?:   \s*$regexp\s*\((?:\s*\([^)]+\))?\s*([^)]+)\)|
 138                 \s*\{\s*$regexp\s*\((?:\s*\([^)]+\))?\s*([^)]+)\)\s*;\s*\}))/sxg)
 139             {
 140               my $all = $1;
 141               my ($lhs, $rhs) = ($2, $3);
 142               my ($free_opnd, $braced_free_opnd) = ($4, $5);
 143               my $non_NULL;
 144               if (!defined $rhs) { $non_NULL = $lhs }
 145               elsif (is_NULL $rhs) { $non_NULL = $lhs }
 146               elsif (is_NULL $lhs) { $non_NULL = $rhs }
 147               else { next }
 148
 149               # Compare the non-NULL part of the "if" expression and the
 150               # free'd expression, without regard to white space.
 151               $non_NULL =~ tr/ \t//d;
 152               my $e2 = defined $free_opnd ? $free_opnd : $braced_free_opnd;
 153               $e2 =~ tr/ \t//d;
 154               if ($non_NULL eq $e2)
 155                 {
 156                   $found_match = 1;
 157                   $list
 158                     and (print "$file\0"), next FILE;
 159                   print "$file: $all\n";
 160                 }
 161             }
 162         }
 163     }
 164   continue
 165     {
 166       close FH;
 167     }
 168
 169   $found_match && $err == EXIT_NO_MATCH
 170     and $err = EXIT_MATCH;
 171
 172   exit $err;
 173 }
 174
 175 my $foo = <<'EOF';
 176 # The above is to *find* them.
 177 # This adjusts them, removing the unnecessary "if (p)" part.
 178
 179 # FIXME: do something like this as an option (doesn't do braces):
 180 free=xfree
 181 git grep -l -z "$free *(" \
 182   | xargs -0 useless-if-before-free -l --name="$free" \
 183   | xargs -0 perl -0x3b -pi -e \
 184    's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*(?:0|NULL))?\s*\)\s+('"$free"'\s*\((?:\s*\([^)]+\))?\s*\1\s*\))/$2/s'
 185
 186 # Use the following to remove redundant uses of kfree inside braces.
 187 # Note that -0777 puts perl in slurp-whole-file mode;
 188 # but we have plenty of memory, these days...
 189 free=kfree
 190 git grep -l -z "$free *(" \
 191   | xargs -0 useless-if-before-free -l --name="$free" \
 192   | xargs -0 perl -0777 -pi -e \
 193      's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*(?:0|NULL))?\s*\)\s*\{\s*('"$free"'\s*\((?:\s*\([^)]+\))?\s*\1\s*\);)\s*\}[^\n]*$/$2/gms'
 194
 195 Be careful that the result of the above transformation is valid.
 196 If the matched string is followed by "else", then obviously, it won't be.
 197
 198 When modifying files, refuse to process anything other than a regular file.
 199 EOF
 200
 201 ## Local Variables:
 202 ## mode: perl
 203 ## indent-tabs-mode: nil
 204 ## eval: (add-hook 'write-file-hooks 'time-stamp)
 205 ## time-stamp-start: "my $VERSION = '"
 206 ## time-stamp-format: "%:y-%02m-%02d %02H:%02M"
 207 ## time-stamp-time-zone: "UTC"
 208 ## time-stamp-end: "'; # UTC"
 209 ## End: