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 "if (p != 0)", "if (0 != p)", or with NULL; and with braces.
   6
   7 my $VERSION = '2012-01-06 07:23'; # UTC
   8 # The definition above must lie within the first 8 lines in order
   9 # for the Emacs time-stamp write hook (at end) to update it.
  10 # If you change this file with Emacs, please let the write hook
  11 # do its job.  Otherwise, update this string manually.
  12
  13 # Copyright (C) 2008-2014 Free Software Foundation, Inc.
  14
  15 # This program is free software: you can redistribute it and/or modify
  16 # it under the terms of the GNU General Public License as published by
  17 # the Free Software Foundation, either version 3 of the License, or
  18 # (at your option) any later version.
  19
  20 # This program is distributed in the hope that it will be useful,
  21 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 # GNU General Public License for more details.
  24
  25 # You should have received a copy of the GNU General Public License
  26 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  27
  28 # Written by Jim Meyering
  29
  30 use strict;
  31 use warnings;
  32 use Getopt::Long;
  33
  34 (my $ME = $0) =~ s|.*/||;
  35
  36 # use File::Coda; # http://meyering.net/code/Coda/
  37 END {
  38   defined fileno STDOUT or return;
  39   close STDOUT and return;
  40   warn "$ME: failed to close standard output: $!\n";
  41   $? ||= 1;
  42 }
  43
  44 sub usage ($)
  45 {
  46   my ($exit_code) = @_;
  47   my $STREAM = ($exit_code == 0 ? *STDOUT : *STDERR);
  48   if ($exit_code != 0)
  49     {
  50       print $STREAM "Try '$ME --help' for more information.\n";
  51     }
  52   else
  53     {
  54       print $STREAM <<EOF;
  55 Usage: $ME [OPTIONS] FILE...
  56
  57 Detect any instance in FILE of a useless "if" test before a free call, e.g.,
  58 "if (p) free (p);".  Any such test may be safely removed without affecting
  59 the semantics of the C code in FILE.  Use --name=FOO --name=BAR to also
  60 detect free-like functions named FOO and BAR.
  61
  62 OPTIONS:
  63
  64    --list       print only the name of each matching FILE (\\0-terminated)
  65    --name=N     add name N to the list of \'free\'-like functions to detect;
  66                   may be repeated
  67
  68    --help       display this help and exit
  69    --version    output version information and exit
  70
  71 Exit status:
  72
  73   0   one or more matches
  74   1   no match
  75   2   an error
  76
  77 EXAMPLE:
  78
  79 For example, this command prints all removable "if" tests before "free"
  80 and "kfree" calls in the linux kernel sources:
  81
  82     git ls-files -z |xargs -0 $ME --name=kfree
  83
  84 EOF
  85     }
  86   exit $exit_code;
  87 }
  88
  89 sub is_NULL ($)
  90 {
  91   my ($expr) = @_;
  92   return ($expr eq 'NULL' || $expr eq '0');
  93 }
  94
  95 {
  96   sub EXIT_MATCH {0}
  97   sub EXIT_NO_MATCH {1}
  98   sub EXIT_ERROR {2}
  99   my $err = EXIT_NO_MATCH;
 100
 101   my $list;
 102   my @name = qw(free);
 103   GetOptions
 104     (
 105      help => sub { usage 0 },
 106      version => sub { print "$ME version $VERSION\n"; exit },
 107      list => \$list,
 108      'name=s@' => \@name,
 109     ) or usage 1;
 110
 111   # Make sure we have the right number of non-option arguments.
 112   # Always tell the user why we fail.
 113   @ARGV < 1
 114     and (warn "$ME: missing FILE argument\n"), usage EXIT_ERROR;
 115
 116   my $or = join '|', @name;
 117   my $regexp = qr/(?:$or)/;
 118
 119   # Set the input record separator.
 120   # Note: this makes it impractical to print line numbers.
 121   $/ = '"';
 122
 123   my $found_match = 0;
 124  FILE:
 125   foreach my $file (@ARGV)
 126     {
 127       open FH, '<', $file
 128         or (warn "$ME: can't open '$file' for reading: $!\n"),
 129           $err = EXIT_ERROR, next;
 130       while (defined (my $line = <FH>))
 131         {
 132           while ($line =~
 133               /\b(if\s*\(\s*([^)]+?)(?:\s*!=\s*([^)]+?))?\s*\)
 134               #  1          2                  3
 135                (?:   \s*$regexp\s*\((?:\s*\([^)]+\))?\s*([^)]+)\)\s*;|
 136                 \s*\{\s*$regexp\s*\((?:\s*\([^)]+\))?\s*([^)]+)\)\s*;\s*\}))/sxg)
 137             {
 138               my $all = $1;
 139               my ($lhs, $rhs) = ($2, $3);
 140               my ($free_opnd, $braced_free_opnd) = ($4, $5);
 141               my $non_NULL;
 142               if (!defined $rhs) { $non_NULL = $lhs }
 143               elsif (is_NULL $rhs) { $non_NULL = $lhs }
 144               elsif (is_NULL $lhs) { $non_NULL = $rhs }
 145               else { next }
 146
 147               # Compare the non-NULL part of the "if" expression and the
 148               # free'd expression, without regard to white space.
 149               $non_NULL =~ tr/ \t//d;
 150               my $e2 = defined $free_opnd ? $free_opnd : $braced_free_opnd;
 151               $e2 =~ tr/ \t//d;
 152               if ($non_NULL eq $e2)
 153                 {
 154                   $found_match = 1;
 155                   $list
 156                     and (print "$file\0"), next FILE;
 157                   print "$file: $all\n";
 158                 }
 159             }
 160         }
 161     }
 162   continue
 163     {
 164       close FH;
 165     }
 166
 167   $found_match && $err == EXIT_NO_MATCH
 168     and $err = EXIT_MATCH;
 169
 170   exit $err;
 171 }
 172
 173 my $foo = <<'EOF';
 174 # The above is to *find* them.
 175 # This adjusts them, removing the unnecessary "if (p)" part.
 176
 177 # FIXME: do something like this as an option (doesn't do braces):
 178 free=xfree
 179 git grep -l -z "$free *(" \
 180   | xargs -0 useless-if-before-free -l --name="$free" \
 181   | xargs -0 perl -0x3b -pi -e \
 182    's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*(?:0|NULL))?\s*\)\s+('"$free"'\s*\((?:\s*\([^)]+\))?\s*\1\s*\)\s*;)/$2/s'
 183
 184 # Use the following to remove redundant uses of kfree inside braces.
 185 # Note that -0777 puts perl in slurp-whole-file mode;
 186 # but we have plenty of memory, these days...
 187 free=kfree
 188 git grep -l -z "$free *(" \
 189   | xargs -0 useless-if-before-free -l --name="$free" \
 190   | xargs -0 perl -0777 -pi -e \
 191      's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*(?:0|NULL))?\s*\)\s*\{\s*('"$free"'\s*\((?:\s*\([^)]+\))?\s*\1\s*\);)\s*\}[^\n]*$/$2/gms'
 192
 193 Be careful that the result of the above transformation is valid.
 194 If the matched string is followed by "else", then obviously, it won't be.
 195
 196 When modifying files, refuse to process anything other than a regular file.
 197 EOF
 198
 199 ## Local Variables:
 200 ## mode: perl
 201 ## indent-tabs-mode: nil
 202 ## eval: (add-hook 'write-file-hooks 'time-stamp)
 203 ## time-stamp-start: "my $VERSION = '"
 204 ## time-stamp-format: "%:y-%02m-%02d %02H:%02M"
 205 ## time-stamp-time-zone: "UTC"
 206 ## time-stamp-end: "'; # UTC"
 207 ## End: