[PATCH] git-svn: Don't rely on $_ after making a function call

[PATCH] git-svn: Don't rely on $_ after making a function call

[Adam Roben]

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 <aroben@apple.com>
---
 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

Re: [PATCH] git-svn: Don't rely on $_ after making a function call

[Eric Wong]

Adam Roben <aroben@apple.com> 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 <normalperson@yhbt.net>

> Signed-off-by: Adam Roben <aroben@apple.com>
> ---
>  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

Re: [PATCH] git-svn: Don't rely on $_ after making a function call

[Adam Roben]

On Apr 25, 2007, at 1:59 PM, Eric Wong wrote:

> Adam Roben <aroben@apple.com> 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

Re: [PATCH] git-svn: Don't rely on $_ after making a function call

[Junio C Hamano]

Eric Wong <normalperson@yhbt.net> writes:

> Adam Roben <aroben@apple.com> 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.

Re: [PATCH] git-svn: Don't rely on $_ after making a function call

[Randal L. Schwartz]

>>>>> "Junio" == Junio C Hamano <junkio@cox.net> 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
<merlyn@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
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