Linux build: Use sysroot when calculating dependencies

third_party/dpkg-dev/scripts/Dpkg/Source/Patch.pm

Index: third_party/dpkg-dev/scripts/Dpkg/Source/Patch.pm
diff --git a/third_party/dpkg-dev/scripts/Dpkg/Source/Patch.pm b/third_party/dpkg-dev/scripts/Dpkg/Source/Patch.pm
new file mode 100644
index 0000000000000000000000000000000000000000..a3fb8460e828df7f784609299c9c3bdd8afebe7e
--- /dev/null
+++ b/third_party/dpkg-dev/scripts/Dpkg/Source/Patch.pm
@@ -0,0 +1,640 @@
+# Copyright © 2008 Raphaël Hertzog <hertzog@debian.org>
+#
+# 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 2 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/>.
+
+package Dpkg::Source::Patch;
+
+use strict;
+use warnings;
+
+our $VERSION = '0.01';
+
+use Dpkg;
+use Dpkg::Gettext;
+use Dpkg::IPC;
+use Dpkg::ErrorHandling;
+use Dpkg::Source::Functions qw(fs_time);
+
+use POSIX qw(:errno_h :sys_wait_h);
+use File::Find;
+use File::Basename;
+use File::Spec;
+use File::Path;
+use File::Compare;
+use Fcntl ':mode';
+#XXX: Needed for sub-second timestamps, require recent perl
+#use Time::HiRes qw(stat);
+
+use parent qw(Dpkg::Compression::FileHandle);
+
+sub create {
+    my ($self, %opts) = @_;
+    $self->ensure_open('w'); # Creates the file
+    *$self->{errors} = 0;
+    *$self->{empty} = 1;
+    if ($opts{old} and $opts{new}) {
+        $opts{old} = '/dev/null' unless -e $opts{old};
+        $opts{new} = '/dev/null' unless -e $opts{new};
+        if (-d $opts{old} and -d $opts{new}) {
+            $self->add_diff_directory($opts{old}, $opts{new}, %opts);
+        } elsif (-f $opts{old} and -f $opts{new}) {
+            $self->add_diff_file($opts{old}, $opts{new}, %opts);
+        } else {
+            $self->_fail_not_same_type($opts{old}, $opts{new});
+        }
+        $self->finish() unless $opts{nofinish};
+    }
+}
+
+sub set_header {
+    my ($self, $header) = @_;
+    *$self->{header} = $header;
+}
+
+sub add_diff_file {
+    my ($self, $old, $new, %opts) = @_;
+    $opts{include_timestamp} = 0 unless exists $opts{include_timestamp};
+    my $handle_binary = $opts{handle_binary_func} || sub {
+        my ($self, $old, $new) = @_;
+        $self->_fail_with_msg($new, _g('binary file contents changed'));
+    };
+    # Optimization to avoid forking diff if unnecessary
+    return 1 if compare($old, $new, 4096) == 0;
+    # Default diff options
+    my @options;
+    if ($opts{options}) {
+        push @options, @{$opts{options}};
+    } else {
+        push @options, '-p';
+    }
+    # Add labels
+    if ($opts{label_old} and $opts{label_new}) {
+	if ($opts{include_timestamp}) {
+	    my $ts = (stat($old))[9];
+	    my $t = POSIX::strftime('%Y-%m-%d %H:%M:%S', gmtime($ts));
+	    $opts{label_old} .= sprintf("\t%s.%09d +0000", $t,
+	                                ($ts - int($ts)) * 1_000_000_000);
+	    $ts = (stat($new))[9];
+	    $t = POSIX::strftime('%Y-%m-%d %H:%M:%S', gmtime($ts));
+	    $opts{label_new} .= sprintf("\t%s.%09d +0000", $t,
+	                                ($ts - int($ts)) * 1_000_000_000);
+	} else {
+	    # Space in filenames need special treatment
+	    $opts{label_old} .= "\t" if $opts{label_old} =~ / /;
+	    $opts{label_new} .= "\t" if $opts{label_new} =~ / /;
+	}
+        push @options, '-L', $opts{label_old},
+                       '-L', $opts{label_new};
+    }
+    # Generate diff
+    my $diffgen;
+    my $diff_pid = spawn(
+        exec => [ 'diff', '-u', @options, '--', $old, $new ],
+        env => { LC_ALL => 'C', LANG => 'C', TZ => 'UTC0' },
+        to_pipe => \$diffgen,
+    );
+    # Check diff and write it in patch file
+    my $difflinefound = 0;
+    my $binary = 0;
+    while (<$diffgen>) {
+        if (m/^(?:binary|[^-+\@ ].*\bdiffer\b)/i) {
+            $binary = 1;
+            &$handle_binary($self, $old, $new);
+            last;
+        } elsif (m/^[-+\@ ]/) {
+            $difflinefound++;
+        } elsif (m/^\\ /) {
+            warning(_g('file %s has no final newline (either ' .
+                       'original or modified version)'), $new);
+        } else {
+            chomp;
+            error(_g("unknown line from diff -u on %s: `%s'"), $new, $_);
+        }
+	if (*$self->{empty} and defined(*$self->{header})) {
+	    $self->print(*$self->{header}) or syserr(_g('failed to write'));
+	    *$self->{empty} = 0;
+	}
+        print { $self } $_ or syserr(_g('failed to write'));
+    }
+    close($diffgen) or syserr('close on diff pipe');
+    wait_child($diff_pid, nocheck => 1,
+               cmdline => "diff -u @options -- $old $new");
+    # Verify diff process ended successfully
+    # Exit code of diff: 0 => no difference, 1 => diff ok, 2 => error
+    # Ignore error if binary content detected
+    my $exit = WEXITSTATUS($?);
+    unless (WIFEXITED($?) && ($exit == 0 || $exit == 1 || $binary)) {
+        subprocerr(_g('diff on %s'), $new);
+    }
+    return ($exit == 0 || $exit == 1);
+}
+
+sub add_diff_directory {
+    my ($self, $old, $new, %opts) = @_;
+    # TODO: make this function more configurable
+    # - offer to disable some checks
+    my $basedir = $opts{basedirname} || basename($new);
+    my $inc_removal = $opts{include_removal} || 0;
+    my $diff_ignore;
+    if ($opts{diff_ignore_func}) {
+        $diff_ignore = $opts{diff_ignore_func};
+    } elsif ($opts{diff_ignore_regex}) {
+        $diff_ignore = sub { return $_[0] =~ /$opts{diff_ignore_regex}/o };
+    } else {
+        $diff_ignore = sub { return 0 };
+    }
+
+    my @diff_files;
+    my %files_in_new;
+    my $scan_new = sub {
+        my $fn = (length > length($new)) ? substr($_, length($new) + 1) : '.';
+        return if &$diff_ignore($fn);
+        $files_in_new{$fn} = 1;
+        lstat("$new/$fn") or syserr(_g('cannot stat file %s'), "$new/$fn");
+        my $mode = S_IMODE((lstat(_))[2]);
+        my $size = (lstat(_))[7];
+        if (-l _) {
+            unless (-l "$old/$fn") {
+                $self->_fail_not_same_type("$old/$fn", "$new/$fn");
+                return;
+            }
+            my $n = readlink("$new/$fn");
+            unless (defined $n) {
+                syserr(_g('cannot read link %s'), "$new/$fn");
+            }
+            my $n2 = readlink("$old/$fn");
+            unless (defined $n2) {
+                syserr(_g('cannot read link %s'), "$old/$fn");
+            }
+            unless ($n eq $n2) {
+                $self->_fail_not_same_type("$old/$fn", "$new/$fn");
+            }
+        } elsif (-f _) {
+            my $old_file = "$old/$fn";
+            if (not lstat("$old/$fn")) {
+                if ($! != ENOENT) {
+                    syserr(_g('cannot stat file %s'), "$old/$fn");
+                }
+                $old_file = '/dev/null';
+            } elsif (not -f _) {
+                $self->_fail_not_same_type("$old/$fn", "$new/$fn");
+                return;
+            }
+
+            my $label_old = "$basedir.orig/$fn";
+            if ($opts{use_dev_null}) {
+                $label_old = $old_file if $old_file eq '/dev/null';
+            }
+            push @diff_files, [$fn, $mode, $size, $old_file, "$new/$fn",
+                               $label_old, "$basedir/$fn"];
+        } elsif (-p _) {
+            unless (-p "$old/$fn") {
+                $self->_fail_not_same_type("$old/$fn", "$new/$fn");
+            }
+        } elsif (-b _ || -c _ || -S _) {
+            $self->_fail_with_msg("$new/$fn",
+                _g('device or socket is not allowed'));
+        } elsif (-d _) {
+            if (not lstat("$old/$fn")) {
+                if ($! != ENOENT) {
+                    syserr(_g('cannot stat file %s'), "$old/$fn");
+                }
+            } elsif (not -d _) {
+                $self->_fail_not_same_type("$old/$fn", "$new/$fn");
+            }
+        } else {
+            $self->_fail_with_msg("$new/$fn", _g('unknown file type'));
+        }
+    };
+    my $scan_old = sub {
+        my $fn = (length > length($old)) ? substr($_, length($old) + 1) : '.';
+        return if &$diff_ignore($fn);
+        return if $files_in_new{$fn};
+        lstat("$old/$fn") or syserr(_g('cannot stat file %s'), "$old/$fn");
+        if (-f _) {
+            if ($inc_removal) {
+                push @diff_files, [$fn, 0, 0, "$old/$fn", '/dev/null',
+                                   "$basedir.orig/$fn", '/dev/null'];
+            } else {
+                warning(_g('ignoring deletion of file %s'), $fn);
+            }
+        } elsif (-d _) {
+            warning(_g('ignoring deletion of directory %s'), $fn);
+        } elsif (-l _) {
+            warning(_g('ignoring deletion of symlink %s'), $fn);
+        } else {
+            $self->_fail_not_same_type("$old/$fn", "$new/$fn");
+        }
+    };
+
+    find({ wanted => $scan_new, no_chdir => 1 }, $new);
+    find({ wanted => $scan_old, no_chdir => 1 }, $old);
+
+    if ($opts{order_from} and -e $opts{order_from}) {
+        my $order_from = Dpkg::Source::Patch->new(
+            filename => $opts{order_from});
+        my $analysis = $order_from->analyze($basedir, verbose => 0);
+        my %patchorder;
+        my $i = 0;
+        foreach my $fn (@{$analysis->{patchorder}}) {
+            $fn =~ s{^[^/]+/}{};
+            $patchorder{$fn} = $i++;
+        }
+        # 'quilt refresh' sorts files as follows:
+        #   - Any files in the existing patch come first, in the order in
+        #     which they appear in the existing patch.
+        #   - New files follow, sorted lexicographically.
+        # This seems a reasonable policy to follow, and avoids autopatches
+        # being shuffled when they are regenerated.
+        foreach my $diff_file (sort { $a->[0] cmp $b->[0] } @diff_files) {
+            my $fn = $diff_file->[0];
+            $patchorder{$fn} = $i++ unless exists $patchorder{$fn};
+        }
+        @diff_files = sort { $patchorder{$a->[0]} <=> $patchorder{$b->[0]} }
+                      @diff_files;
+    } else {
+        @diff_files = sort { $a->[0] cmp $b->[0] } @diff_files;
+    }
+
+    foreach my $diff_file (@diff_files) {
+        my ($fn, $mode, $size,
+            $old_file, $new_file, $label_old, $label_new) = @$diff_file;
+        my $success = $self->add_diff_file($old_file, $new_file,
+                                           label_old => $label_old,
+                                           label_new => $label_new, %opts);
+        if ($success and
+            $old_file eq '/dev/null' and $new_file ne '/dev/null') {
+            if (not $size) {
+                warning(_g("newly created empty file '%s' will not " .
+                           'be represented in diff'), $fn);
+            } else {
+                if ($mode & (S_IXUSR | S_IXGRP | S_IXOTH)) {
+                    warning(_g("executable mode %04o of '%s' will " .
+                               'not be represented in diff'), $mode, $fn)
+                        unless $fn eq 'debian/rules';
+                }
+                if ($mode & (S_ISUID | S_ISGID | S_ISVTX)) {
+                    warning(_g("special mode %04o of '%s' will not " .
+                               'be represented in diff'), $mode, $fn);
+                }
+            }
+        }
+    }
+}
+
+sub finish {
+    my ($self) = @_;
+    close($self) or syserr(_g('cannot close %s'), $self->get_filename());
+    return not *$self->{errors};
+}
+
+sub register_error {
+    my ($self) = @_;
+    *$self->{errors}++;
+}
+sub _fail_with_msg {
+    my ($self, $file, $msg) = @_;
+    errormsg(_g('cannot represent change to %s: %s'), $file, $msg);
+    $self->register_error();
+}
+sub _fail_not_same_type {
+    my ($self, $old, $new) = @_;
+    my $old_type = get_type($old);
+    my $new_type = get_type($new);
+    errormsg(_g('cannot represent change to %s:'), $new);
+    errormsg(_g('  new version is %s'), $new_type);
+    errormsg(_g('  old version is %s'), $old_type);
+    $self->register_error();
+}
+
+sub _getline {
+    my $handle = shift;
+
+    my $line = <$handle>;
+    if (defined $line) {
+        # Strip end-of-line chars
+        chomp($line);
+        $line =~ s/\r$//;
+    }
+    return $line;
+}
+
+sub _intuit_file_patched {
+    my ($old, $new) = @_;
+
+    return $new unless defined $old;
+    return $old unless defined $new;
+    return $new if -e $new and not -e $old;
+    return $old if -e $old and not -e $new;
+
+    # We don't consider the case where both files are non-existent and
+    # where patch picks the one with the fewest directories to create
+    # since dpkg-source will pre-create the required directories
+
+    # Precalculate metrics used by patch
+    my ($tmp_o, $tmp_n) = ($old, $new);
+    my ($len_o, $len_n) = (length($old), length($new));
+    $tmp_o =~ s{[/\\]+}{/}g;
+    $tmp_n =~ s{[/\\]+}{/}g;
+    my $nb_comp_o = ($tmp_o =~ tr{/}{/});
+    my $nb_comp_n = ($tmp_n =~ tr{/}{/});
+    $tmp_o =~ s{^.*/}{};
+    $tmp_n =~ s{^.*/}{};
+    my ($blen_o, $blen_n) = (length($tmp_o), length($tmp_n));
+
+    # Decide like patch would
+    if ($nb_comp_o != $nb_comp_n) {
+        return ($nb_comp_o < $nb_comp_n) ? $old : $new;
+    } elsif ($blen_o != $blen_n) {
+        return ($blen_o < $blen_n) ? $old : $new;
+    } elsif ($len_o != $len_n) {
+        return ($len_o < $len_n) ? $old : $new;
+    }
+    return $old;
+}
+
+# Fetch the header filename ignoring the optional timestamp
+sub _fetch_filename {
+    my ($diff, $header) = @_;
+
+    # Strip any leading spaces.
+    $header =~ s/^\s+//;
+
+    # Is it a C-style string?
+    if ($header =~ m/^"/) {
+        error(_g('diff %s patches file with C-style encoded filename'), $diff);
+    } else {
+        # Tab is the official separator, it's always used when
+        # filename contain spaces. Try it first, otherwise strip on space
+        # if there's no tab
+        $header =~ s/\s.*// unless $header =~ s/\t.*//;
+    }
+
+    return $header;
+}
+
+# check diff for sanity, find directories to create as a side effect
+sub analyze {
+    my ($self, $destdir, %opts) = @_;
+
+    $opts{verbose} //= 1;
+    my $diff = $self->get_filename();
+    my %filepatched;
+    my %dirtocreate;
+    my @patchorder;
+    my $patch_header = '';
+    my $diff_count = 0;
+
+    $_ = _getline($self);
+
+  HUNK:
+    while (defined($_) or not eof($self)) {
+	my (%path, %fn);
+	# skip comments leading up to patch (if any)
+	while (1) {
+	    if (/^(?:--- |\+\+\+ |@@ -)/) {
+		last;
+	    } else {
+		$patch_header .= "$_\n";
+	    }
+	    last HUNK if not defined($_ = _getline($self));
+	}
+	$diff_count++;
+	# read file header (---/+++ pair)
+	unless(s/^--- //) {
+	    error(_g("expected ^--- in line %d of diff `%s'"), $., $diff);
+	}
+        $path{old} = $_ = _fetch_filename($diff, $_);
+	$fn{old} = $_ if $_ ne '/dev/null' and s{^[^/]*/+}{$destdir/};
+	if (/\.dpkg-orig$/) {
+	    error(_g("diff `%s' patches file with name ending .dpkg-orig"), $diff);
+	}
+
+	unless (defined($_ = _getline($self))) {
+	    error(_g("diff `%s' finishes in middle of ---/+++ (line %d)"), $diff, $.);
+	}
+	unless (s/^\+\+\+ //) {
+	    error(_g("line after --- isn't as expected in diff `%s' (line %d)"), $diff, $.);
+	}
+        $path{new} = $_ = _fetch_filename($diff, $_);
+	$fn{new} = $_ if $_ ne '/dev/null' and s{^[^/]*/+}{$destdir/};
+
+	unless (defined $fn{old} or defined $fn{new}) {
+	    error(_g("none of the filenames in ---/+++ are valid in diff '%s' (line %d)"),
+		  $diff, $.);
+	}
+
+	# Safety checks on both filenames that patch could use
+	foreach my $key ('old', 'new') {
+	    next unless defined $fn{$key};
+	    if ($path{$key} =~ m{/\.\./}) {
+		error(_g('%s contains an insecure path: %s'), $diff, $path{$key});
+	    }
+	    my $path = $fn{$key};
+	    while (1) {
+		if (-l $path) {
+		    error(_g('diff %s modifies file %s through a symlink: %s'),
+			  $diff, $fn{$key}, $path);
+		}
+		last unless $path =~ s{/+[^/]*$}{};
+		last if length($path) <= length($destdir); # $destdir is assumed safe
+	    }
+	}
+
+        if ($path{old} eq '/dev/null' and $path{new} eq '/dev/null') {
+            error(_g("original and modified files are /dev/null in diff `%s' (line %d)"),
+                  $diff, $.);
+        } elsif ($path{new} eq '/dev/null') {
+            error(_g("file removal without proper filename in diff `%s' (line %d)"),
+                  $diff, $. - 1) unless defined $fn{old};
+            if ($opts{verbose}) {
+                warning(_g('diff %s removes a non-existing file %s (line %d)'),
+                        $diff, $fn{old}, $.) unless -e $fn{old};
+            }
+        }
+	my $fn = _intuit_file_patched($fn{old}, $fn{new});
+
+	my $dirname = $fn;
+	if ($dirname =~ s{/[^/]+$}{} and not -d $dirname) {
+	    $dirtocreate{$dirname} = 1;
+	}
+
+	if (-e $fn and not -f _) {
+	    error(_g("diff `%s' patches something which is not a plain file"), $diff);
+	}
+
+	if ($filepatched{$fn}) {
+	    warning(_g("diff `%s' patches file %s twice"), $diff, $fn)
+		if $opts{verbose};
+	} else {
+	    $filepatched{$fn} = 1;
+	    push @patchorder, $fn;
+	}
+
+	# read hunks
+	my $hunk = 0;
+	while (defined($_ = _getline($self))) {
+	    # read hunk header (@@)
+	    next if /^\\ /;
+	    last unless (/^@@ -\d+(,(\d+))? \+\d+(,(\d+))? @\@( .*)?$/);
+	    my ($olines, $nlines) = ($1 ? $2 : 1, $3 ? $4 : 1);
+	    # read hunk
+	    while ($olines || $nlines) {
+		unless (defined($_ = _getline($self))) {
+                    if (($olines == $nlines) and ($olines < 3)) {
+                        warning(_g("unexpected end of diff `%s'"), $diff)
+                            if $opts{verbose};
+                        last;
+                    } else {
+                        error(_g("unexpected end of diff `%s'"), $diff);
+                    }
+		}
+		next if /^\\ /;
+		# Check stats
+		if    (/^ / || /^$/)  { --$olines; --$nlines; }
+		elsif (/^-/)  { --$olines; }
+		elsif (/^\+/) { --$nlines; }
+		else {
+		    error(_g("expected [ +-] at start of line %d of diff `%s'"),
+		          $., $diff);
+		}
+	    }
+	    $hunk++;
+	}
+	unless($hunk) {
+	    error(_g("expected ^\@\@ at line %d of diff `%s'"), $., $diff);
+	}
+    }
+    close($self);
+    unless ($diff_count) {
+	warning(_g("diff `%s' doesn't contain any patch"), $diff)
+	    if $opts{verbose};
+    }
+    *$self->{analysis}{$destdir}{dirtocreate} = \%dirtocreate;
+    *$self->{analysis}{$destdir}{filepatched} = \%filepatched;
+    *$self->{analysis}{$destdir}{patchorder} = \@patchorder;
+    *$self->{analysis}{$destdir}{patchheader} = $patch_header;
+    return *$self->{analysis}{$destdir};
+}
+
+sub prepare_apply {
+    my ($self, $analysis, %opts) = @_;
+    if ($opts{create_dirs}) {
+	foreach my $dir (keys %{$analysis->{dirtocreate}}) {
+	    eval { mkpath($dir, 0, 0777); };
+	    syserr(_g('cannot create directory %s'), $dir) if $@;
+	}
+    }
+}
+
+sub apply {
+    my ($self, $destdir, %opts) = @_;
+    # Set default values to options
+    $opts{force_timestamp} = 1 unless exists $opts{force_timestamp};
+    $opts{remove_backup} = 1 unless exists $opts{remove_backup};
+    $opts{create_dirs} = 1 unless exists $opts{create_dirs};
+    $opts{options} ||= [ '-t', '-F', '0', '-N', '-p1', '-u',
+            '-V', 'never', '-g0', '-b', '-z', '.dpkg-orig'];
+    $opts{add_options} ||= [];
+    push @{$opts{options}}, @{$opts{add_options}};
+    # Check the diff and create missing directories
+    my $analysis = $self->analyze($destdir, %opts);
+    $self->prepare_apply($analysis, %opts);
+    # Apply the patch
+    $self->ensure_open('r');
+    my ($stdout, $stderr) = ('', '');
+    spawn(
+	exec => [ 'patch', @{$opts{options}} ],
+	chdir => $destdir,
+	env => { LC_ALL => 'C', LANG => 'C' },
+	delete_env => [ 'POSIXLY_CORRECT' ], # ensure expected patch behaviour
+	wait_child => 1,
+	nocheck => 1,
+	from_handle => $self->get_filehandle(),
+	to_string => \$stdout,
+	error_to_string => \$stderr,
+    );
+    if ($?) {
+	print { *STDOUT } $stdout;
+	print { *STDERR } $stderr;
+	subprocerr('LC_ALL=C patch ' . join(' ', @{$opts{options}}) .
+	           ' < ' . $self->get_filename());
+    }
+    $self->close();
+    # Reset the timestamp of all the patched files
+    # and remove .dpkg-orig files
+    my @files = keys %{$analysis->{filepatched}};
+    my $now = $opts{timestamp};
+    $now ||= fs_time($files[0]) if $opts{force_timestamp} && scalar @files;
+    foreach my $fn (@files) {
+	if ($opts{force_timestamp}) {
+	    utime($now, $now, $fn) or $! == ENOENT
+		or syserr(_g('cannot change timestamp for %s'), $fn);
+	}
+	if ($opts{remove_backup}) {
+	    $fn .= '.dpkg-orig';
+	    unlink($fn) or syserr(_g('remove patch backup file %s'), $fn);
+	}
+    }
+    return $analysis;
+}
+
+# Verify if check will work...
+sub check_apply {
+    my ($self, $destdir, %opts) = @_;
+    # Set default values to options
+    $opts{create_dirs} = 1 unless exists $opts{create_dirs};
+    $opts{options} ||= [ '--dry-run', '-s', '-t', '-F', '0', '-N', '-p1', '-u',
+            '-V', 'never', '-g0', '-b', '-z', '.dpkg-orig'];
+    $opts{add_options} ||= [];
+    push @{$opts{options}}, @{$opts{add_options}};
+    # Check the diff and create missing directories
+    my $analysis = $self->analyze($destdir, %opts);
+    $self->prepare_apply($analysis, %opts);
+    # Apply the patch
+    $self->ensure_open('r');
+    my $patch_pid = spawn(
+	exec => [ 'patch', @{$opts{options}} ],
+	chdir => $destdir,
+	env => { LC_ALL => 'C', LANG => 'C' },
+	delete_env => [ 'POSIXLY_CORRECT' ], # ensure expected patch behaviour
+	from_handle => $self->get_filehandle(),
+	to_file => '/dev/null',
+	error_to_file => '/dev/null',
+    );
+    wait_child($patch_pid, nocheck => 1);
+    my $exit = WEXITSTATUS($?);
+    subprocerr('patch --dry-run') unless WIFEXITED($?);
+    $self->close();
+    return ($exit == 0);
+}
+
+# Helper functions
+sub get_type {
+    my $file = shift;
+    if (not lstat($file)) {
+        return _g('nonexistent') if $! == ENOENT;
+        syserr(_g('cannot stat %s'), $file);
+    } else {
+        -f _ && return _g('plain file');
+        -d _ && return _g('directory');
+        -l _ && return sprintf(_g('symlink to %s'), readlink($file));
+        -b _ && return _g('block device');
+        -c _ && return _g('character device');
+        -p _ && return _g('named pipe');
+        -S _ && return _g('named socket');
+    }
+}
+
+1;