# [PATCH] git-svn: Don't rely on $_ after making a function call 5 messages from 2007-04-25 to 2007-04-26. Participants: Adam Roben, Eric Wong, Junio C Hamano, Randal L. Schwartz. Thread: https://gitlist.dev/t/7841 ## Adam Roben, 2007-04-25 18:50 Subject: [PATCH] git-svn: Don't rely on $_ after making a function call Message-ID: <11775270321427-git-send-email-aroben@apple.com> URL: https://gitlist.dev/e/11775270321427-git-send-email-aroben%40apple.com ``` Many functions and operators in perl set $_, so its value cannot be relied upon after calling arbitrary functions. The solution is simply to copy the value of $_ into a local variable that will not get overwritten. Signed-off-by: Adam Roben --- git-svn.perl | 10 +++++----- 1 files changed, 5 insertions(+), 5 deletions(-) diff --git a/git-svn.perl b/git-svn.perl index 077d6b3..90f3bc1 100755 --- a/git-svn.perl +++ b/git-svn.perl @@ -771,19 +771,19 @@ sub cmt_metadata { sub working_head_info { my ($head, $refs) = @_; my ($fh, $ctx) = command_output_pipe('rev-list', $head); - while (<$fh>) { - chomp; - my ($url, $rev, $uuid) = cmt_metadata($_); + while (my $hash = <$fh>) { + chomp($hash); + my ($url, $rev, $uuid) = cmt_metadata($hash); if (defined $url && defined $rev) { if (my $gs = Git::SVN->find_by_url($url)) { my $c = $gs->rev_db_get($rev); - if ($c && $c eq $_) { + if ($c && $c eq $hash) { close $fh; # break the pipe return ($url, $rev, $uuid, $gs); } } } - unshift @$refs, $_ if $refs; + unshift @$refs, $hash if $refs; } command_close_pipe($fh, $ctx); (undef, undef, undef, undef); -- 1.5.2.rc0.14.g520d-dirty ``` ## Eric Wong, 2007-04-25 20:59 Subject: Re: [PATCH] git-svn: Don't rely on $_ after making a function call Message-ID: <20070425205948.GA12375@untitled> URL: https://gitlist.dev/e/20070425205948.GA12375%40untitled In-Reply-To: <11775270321427-git-send-email-aroben@apple.com> ``` Adam Roben wrote: > Many functions and operators in perl set $_, so its value cannot be relied upon > after calling arbitrary functions. The solution is simply to copy the value of > $_ into a local variable that will not get overwritten. Does this fix any particular bug? It looks right to me and makes the code easier to follow, so; Acked-by: Eric Wong > Signed-off-by: Adam Roben > --- > git-svn.perl | 10 +++++----- > 1 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/git-svn.perl b/git-svn.perl > index 077d6b3..90f3bc1 100755 > --- a/git-svn.perl > +++ b/git-svn.perl > @@ -771,19 +771,19 @@ sub cmt_metadata { > sub working_head_info { > my ($head, $refs) = @_; > my ($fh, $ctx) = command_output_pipe('rev-list', $head); > - while (<$fh>) { > - chomp; > - my ($url, $rev, $uuid) = cmt_metadata($_); > + while (my $hash = <$fh>) { > + chomp($hash); > + my ($url, $rev, $uuid) = cmt_metadata($hash); > if (defined $url && defined $rev) { > if (my $gs = Git::SVN->find_by_url($url)) { > my $c = $gs->rev_db_get($rev); > - if ($c && $c eq $_) { > + if ($c && $c eq $hash) { > close $fh; # break the pipe > return ($url, $rev, $uuid, $gs); > } > } > } > - unshift @$refs, $_ if $refs; > + unshift @$refs, $hash if $refs; > } > command_close_pipe($fh, $ctx); > (undef, undef, undef, undef); > -- > 1.5.2.rc0.14.g520d-dirty > -- Eric Wong ``` ## Adam Roben, 2007-04-25 21:03 Subject: Re: [PATCH] git-svn: Don't rely on $_ after making a function call Message-ID: <3601FA1C-CDB1-4BFE-93D7-8FF1A79DCF45@apple.com> URL: https://gitlist.dev/e/3601FA1C-CDB1-4BFE-93D7-8FF1A79DCF45%40apple.com In-Reply-To: <20070425205948.GA12375@untitled> ``` On Apr 25, 2007, at 1:59 PM, Eric Wong wrote: > Adam Roben wrote: >> Many functions and operators in perl set $_, so its value cannot >> be relied upon >> after calling arbitrary functions. The solution is simply to copy >> the value of >> $_ into a local variable that will not get overwritten. > > Does this fix any particular bug? It looks right to me > and makes the code easier to follow, so; Yes, I was getting warnings that $_ was uninitialized in the eq. Sorry for not mentioning that. -Adam ``` ## Junio C Hamano, 2007-04-25 21:13 Subject: Re: [PATCH] git-svn: Don't rely on $_ after making a function call Message-ID: <7v4pn4w41k.fsf@assigned-by-dhcp.cox.net> URL: https://gitlist.dev/e/7v4pn4w41k.fsf%40assigned-by-dhcp.cox.net In-Reply-To: <20070425205948.GA12375@untitled> ``` Eric Wong writes: > Adam Roben wrote: >> Many functions and operators in perl set $_, so its value cannot be relied upon >> after calling arbitrary functions. The solution is simply to copy the value of >> $_ into a local variable that will not get overwritten. > > Does this fix any particular bug? It looks right to me > and makes the code easier to follow, so; I suspect Merlyn has better explanation, but... for (list) { ... } loop implicitly localizes $_ and does not share this problem, which I really appreciate whenever I am writing Perl code, but often enough I was bitten by scripts that use "while (<$fh>)", which does not localizes $_, and made hard to spot bugs by clobbering $_. I find the patch a good safety measure for any future breakages. ``` ## Randal L. Schwartz, 2007-04-26 02:11 Subject: Re: [PATCH] git-svn: Don't rely on $_ after making a function call Message-ID: <864pn3hokb.fsf@blue.stonehenge.com> URL: https://gitlist.dev/e/864pn3hokb.fsf%40blue.stonehenge.com In-Reply-To: <7v4pn4w41k.fsf@assigned-by-dhcp.cox.net> ``` >>>>> "Junio" == Junio C Hamano writes: Junio> I suspect Merlyn has better explanation, but... Junio> for (list) { Junio> ... Junio> } Junio> loop implicitly localizes $_ and does not share this problem, Junio> which I really appreciate whenever I am writing Perl code, but Junio> often enough I was bitten by scripts that use "while (<$fh>)", Junio> which does not localizes $_, and made hard to spot bugs by Junio> clobbering $_. Junio> I find the patch a good safety measure for any future breakages. I'm happy with the patch. -- Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095 Perl/Unix/security consulting, Technical writing, Comedy, etc. etc. See PerlTraining.Stonehenge.com for onsite and open-enrollment Perl training! ```