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Diffstat (limited to 'build-aux/useless-if-before-free')
| -rwxr-xr-x | build-aux/useless-if-before-free | 240 |
1 files changed, 240 insertions, 0 deletions
diff --git a/build-aux/useless-if-before-free b/build-aux/useless-if-before-free new file mode 100755 index 0000000..1a027a5 --- /dev/null +++ b/build-aux/useless-if-before-free @@ -0,0 +1,240 @@ +#!/bin/sh +#! -*-perl-*- + +# Detect instances of "if (p) free (p);". +# Likewise "if (p != 0)", "if (0 != p)", or with NULL; and with braces. + +# Copyright (C) 2008-2022 Free Software Foundation, Inc. +# +# This program is free software: you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation, either version 3 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <https://www.gnu.org/licenses/>. +# +# Written by Jim Meyering + +# This is a prologue that allows to run a perl script as an executable +# on systems that are compliant to a POSIX version before POSIX:2017. +# On such systems, the usual invocation of an executable through execlp() +# or execvp() fails with ENOEXEC if it is a script that does not start +# with a #! line. The script interpreter mentioned in the #! line has +# to be /bin/sh, because on GuixSD systems that is the only program that +# has a fixed file name. The second line is essential for perl and is +# also useful for editing this file in Emacs. The next two lines below +# are valid code in both sh and perl. When executed by sh, they re-execute +# the script through the perl program found in $PATH. The '-x' option +# is essential as well; without it, perl would re-execute the script +# through /bin/sh. When executed by perl, the next two lines are a no-op. +eval 'exec perl -wSx "$0" "$@"' + if 0; + +my $VERSION = '2022-01-27 18:51'; # UTC +# The definition above must lie within the first 8 lines in order +# for the Emacs time-stamp write hook (at end) to update it. +# If you change this file with Emacs, please let the write hook +# do its job. Otherwise, update this string manually. + +my $copyright_year = '2022'; + +use strict; +use warnings; +use Getopt::Long; + +(my $ME = $0) =~ s|.*/||; + +# use File::Coda; # https://meyering.net/code/Coda/ +END { + defined fileno STDOUT or return; + close STDOUT and return; + warn "$ME: failed to close standard output: $!\n"; + $? ||= 1; +} + +sub usage ($) +{ + my ($exit_code) = @_; + my $STREAM = ($exit_code == 0 ? *STDOUT : *STDERR); + if ($exit_code != 0) + { + print $STREAM "Try '$ME --help' for more information.\n"; + } + else + { + print $STREAM <<EOF; +Usage: $ME [OPTIONS] FILE... + +Detect any instance in FILE of a useless "if" test before a free call, e.g., +"if (p) free (p);". Any such test may be safely removed without affecting +the semantics of the C code in FILE. Use --name=FOO --name=BAR to also +detect free-like functions named FOO and BAR. + +OPTIONS: + + --list print only the name of each matching FILE (\\0-terminated) + --name=N add name N to the list of \'free\'-like functions to detect; + may be repeated + + --help display this help and exit + --version output version information and exit + +Exit status: + + 0 one or more matches + 1 no match + 2 an error + +EXAMPLE: + +For example, this command prints all removable "if" tests before "free" +and "kfree" calls in the linux kernel sources: + + git ls-files -z |xargs -0 $ME --name=kfree + +EOF + } + exit $exit_code; +} + +sub is_NULL ($) +{ + my ($expr) = @_; + return ($expr eq 'NULL' || $expr eq '0'); +} + +{ + sub EXIT_MATCH {0} + sub EXIT_NO_MATCH {1} + sub EXIT_ERROR {2} + my $err = EXIT_NO_MATCH; + + my $list; + my @name = qw(free); + GetOptions + ( + help => sub { usage 0 }, + version => + sub + { + print "$ME version $VERSION\n"; + print "Copyright (C) $copyright_year Free Software Foundation, Inc.\n"; + print "License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.\n" + . "This is free software: you are free to change and redistribute it.\n" + . "There is NO WARRANTY, to the extent permitted by law.\n"; + print "\n"; + my $author = "Jim Meyering"; + print "Written by $author.\n"; + exit + }, + list => \$list, + 'name=s@' => \@name, + ) or usage 1; + + # Make sure we have the right number of non-option arguments. + # Always tell the user why we fail. + @ARGV < 1 + and (warn "$ME: missing FILE argument\n"), usage EXIT_ERROR; + + my $or = join '|', @name; + my $regexp = qr/(?:$or)/; + + # Set the input record separator. + # Note: this makes it impractical to print line numbers. + $/ = '"'; + + my $found_match = 0; + FILE: + foreach my $file (@ARGV) + { + open FH, '<', $file + or (warn "$ME: can't open '$file' for reading: $!\n"), + $err = EXIT_ERROR, next; + while (defined (my $line = <FH>)) + { + # Skip non-matching lines early to save time + $line =~ /\bif\b/ + or next; + while ($line =~ + /\b(if\s*\(\s*([^)]+?)(?:\s*!=\s*([^)]+?))?\s*\) + # 1 2 3 + (?: \s*$regexp\s*\((?:\s*\([^)]+\))?\s*([^)]+)\)\s*;| + \s*\{\s*$regexp\s*\((?:\s*\([^)]+\))?\s*([^)]+)\)\s*;\s*\}))/sxg) + { + my $all = $1; + my ($lhs, $rhs) = ($2, $3); + my ($free_opnd, $braced_free_opnd) = ($4, $5); + my $non_NULL; + if (!defined $rhs) { $non_NULL = $lhs } + elsif (is_NULL $rhs) { $non_NULL = $lhs } + elsif (is_NULL $lhs) { $non_NULL = $rhs } + else { next } + + # Compare the non-NULL part of the "if" expression and the + # free'd expression, without regard to white space. + $non_NULL =~ tr/ \t//d; + my $e2 = defined $free_opnd ? $free_opnd : $braced_free_opnd; + $e2 =~ tr/ \t//d; + if ($non_NULL eq $e2) + { + $found_match = 1; + $list + and (print "$file\0"), next FILE; + print "$file: $all\n"; + } + } + } + } + continue + { + close FH; + } + + $found_match && $err == EXIT_NO_MATCH + and $err = EXIT_MATCH; + + exit $err; +} + +my $foo = <<'EOF'; +# The above is to *find* them. +# This adjusts them, removing the unnecessary "if (p)" part. + +# FIXME: do something like this as an option (doesn't do braces): +free=xfree +git grep -l -z "$free *(" \ + | xargs -0 useless-if-before-free -l --name="$free" \ + | xargs -0 perl -0x3b -pi -e \ + 's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*(?:0|NULL))?\s*\)\s+('"$free"'\s*\((?:\s*\([^)]+\))?\s*\1\s*\)\s*;)/$2/s' + +# Use the following to remove redundant uses of kfree inside braces. +# Note that -0777 puts perl in slurp-whole-file mode; +# but we have plenty of memory, these days... +free=kfree +git grep -l -z "$free *(" \ + | xargs -0 useless-if-before-free -l --name="$free" \ + | xargs -0 perl -0777 -pi -e \ + 's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*(?:0|NULL))?\s*\)\s*\{\s*('"$free"'\s*\((?:\s*\([^)]+\))?\s*\1\s*\);)\s*\}[^\n]*$/$2/gms' + +Be careful that the result of the above transformation is valid. +If the matched string is followed by "else", then obviously, it won't be. + +When modifying files, refuse to process anything other than a regular file. +EOF + +## Local Variables: +## mode: perl +## indent-tabs-mode: nil +## eval: (add-hook 'before-save-hook 'time-stamp) +## time-stamp-line-limit: 50 +## time-stamp-start: "my $VERSION = '" +## time-stamp-format: "%:y-%02m-%02d %02H:%02M" +## time-stamp-time-zone: "UTC0" +## time-stamp-end: "'; # UTC" +## End: |