unusual syntax?

Hi,

i noticed that this doesn't work for me (Perl 5.10):

sub _close_hash_and_insert_object {
	my ($self) = @_;

	return unless defined($self->{hash_object_pid});

	my @vars = map { 'hash_object_' . $_ } qw(pid in out ctx);

	command_close_bidi_pipe($self->{@vars});
	delete $self->{@vars};
}

$self->{@vars} evaluates to undef. i can't find any mention of using arrays to dereference objects in the manual and elsewhere; is this a mistake?

Cheers,
Ray Chuan

---

Yes, @vars would be interpreted in scalar context, which certainly isn't the intended effect.

-- ams

 perl/Git.pm |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

index 087d3d0..2ef437f 100644
@@ -839,8 +839,8 @@ sub _close_hash_and_insert_object {
 
 	my @vars = map { 'hash_object_' . $_ } qw(pid in out ctx);
 
-	command_close_bidi_pipe($self->{@vars});
-	delete $self->{@vars};
+	command_close_bidi_pipe(@$self{@vars});
+	delete @$self{@vars};
 }
 
 =item cat_blob ( SHA1, FILEHANDLE )

@@ -928,8 +928,8 @@ sub _close_cat_blob {
 
 	my @vars = map { 'cat_blob_' . $_ } qw(pid in out ctx);
 
-	command_close_bidi_pipe($self->{@vars});
-	delete $self->{@vars};
+	command_close_bidi_pipe(@$self{@vars});
+	delete @$self{@vars};
 }
 
 =back

1.6.0.rc0.43.g2aa74

The hash_and_insert_object() and cat_blob() helpers were using an incorrect slice-from-ref Perl syntax. This patch fixes that up in the _close_*() helpers and make the _open_*() helpers use the same syntax for consistnecy.

---

Wow, the command_bidi_pipe API really is dirty. Of course, it is
my fault as anyone's since I didn't get around to review the patches introducing it.

 perl/Git.pm |   16 ++++++----------
 1 files changed, 6 insertions(+), 10 deletions(-)

index 087d3d0..0624428 100644
@@ -827,8 +827,7 @@ sub _open_hash_and_insert_object_if_needed {
 
 	return if defined($self->{hash_object_pid});
 
-	($self->{hash_object_pid}, $self->{hash_object_in},
-	 $self->{hash_object_out}, $self->{hash_object_ctx}) =
+	@$self{map { "hash_object_$_" } qw(pid in out ctx)} =
 		command_bidi_pipe(qw(hash-object -w --stdin-paths));
 }
 

@@ -837,9 +836,8 @@ sub _close_hash_and_insert_object {
 
 	return unless defined($self->{hash_object_pid});
 
-	my @vars = map { 'hash_object_' . $_ } qw(pid in out ctx);
-
-	command_close_bidi_pipe($self->{@vars});
+	my @vars = map { "hash_object_$_" } qw(pid in out ctx);
+	command_close_bidi_pipe(@$self{@vars});
 	delete $self->{@vars};
 }
 

@@ -916,8 +914,7 @@ sub _open_cat_blob_if_needed {
 
 	return if defined($self->{cat_blob_pid});
 
-	($self->{cat_blob_pid}, $self->{cat_blob_in},
-	 $self->{cat_blob_out}, $self->{cat_blob_ctx}) =
+	@$self{map { "cat_blob_$_" } qw(pid in out ctx)} =
 		command_bidi_pipe(qw(cat-file --batch));
 }
 

@@ -926,9 +923,8 @@ sub _close_cat_blob {
 
 	return unless defined($self->{cat_blob_pid});
 
-	my @vars = map { 'cat_blob_' . $_ } qw(pid in out ctx);
-
-	command_close_bidi_pipe($self->{@vars});
+	my @vars = map { "cat_blob_$_" } qw(pid in out ctx);
+	command_close_bidi_pipe(@$self{@vars});
 	delete $self->{@vars};
 }
 

Sorry, delete is still broken with your patch, isn't it?

The earlier patch from Abhijit Menon-Sen does this properly for close_hash_and_insert and close_cat_blob, which I've queued already.

Oh, right - I forgot that one and it didn't occur to me to test this part.

Abhijit, can you please tag your Git.pm patches so that I actually have a chance to see and review it?

Thanks,

Petr "Pasky" Baudis

It is $gmane/91316, Message-ID: <[email protected]>

After queueing it, I actually had to revert it, because it seems to break git-svn (t9106-git-svn-commit-diff-clobber.sh, test #8), and I am about to go to bed. If you did not see the same breakage with your patch that does not "fix" delete, it could be that the git-svn uses some of the resources that are released by the delete actually doing what it is asked to do.

---

Yes, @vars would be interpreted in scalar context, which certainly isn't the intended effect.

-- ams

 perl/Git.pm |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

index 087d3d0..2ef437f 100644
@@ -839,8 +839,8 @@ sub _close_hash_and_insert_object {
 
 	my @vars = map { 'hash_object_' . $_ } qw(pid in out ctx);
 
-	command_close_bidi_pipe($self->{@vars});
-	delete $self->{@vars};
+	command_close_bidi_pipe(@$self{@vars});
+	delete @$self{@vars};
 }
 
 =item cat_blob ( SHA1, FILEHANDLE )

@@ -928,8 +928,8 @@ sub _close_cat_blob {
 
 	my @vars = map { 'cat_blob_' . $_ } qw(pid in out ctx);
 
-	command_close_bidi_pipe($self->{@vars});
-	delete $self->{@vars};
+	command_close_bidi_pipe(@$self{@vars});
+	delete @$self{@vars};
 }
 
 =back

1.6.0.rc0.43.g2aa74

Git::DESTROY calls _close_cat_blob and _close_hash_and_insert_object, which in turn call command_close_bidi_pipe, which calls waitpid, which alters $?. If this happens during global destruction, it may alter the program's exit status unexpectedly. Making $? local to the function solves the problem.

(The problem was discovered due to a failure of test #8 in t9106-git-svn-commit-diff-clobber.sh.)

---

This patch in addition to my earlier one should solve the problem.

For test #8 to fail, the "git svn dcommit" must succeed, but in both cases (i.e. without my patch applied, or with), the rebase fails:

rebase refs/remotes/git-svn: command returned error: 1

This results in a call to "fatal $@" on git-svn.perl:254, which calls "exit 1", and test_must_fail is happy.

With my patch, however, Git::DESTROY calls the two _close functions during global destruction, which in turn call command_close_bidi_pipe, which calls waitpid with sensible arguments this time, which alters $?, thus altering the exit status of the dcommit itself to 0. Oops.

All of "make test" passes for me after this change.

-- ams

 perl/Git.pm |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

index 2ef437f..3b6707b 100644
@@ -417,6 +417,7 @@ have more complicated structure.
 =cut
 
 sub command_close_bidi_pipe {
+	local $?;
 	my ($pid, $in, $out, $ctx) = @_;
 	foreach my $fh ($in, $out) {
 		unless (close $fh) {

1.6.0.rc0.43.g2aa74

Thanks.

This is a hash slice notation, returning an array of hash values matching the corresponding keys. 5.10 removed some syntax warts in the case of hash slices; this is more portably expressed as @{$self}{@vars}; this should work in 5.10 and earlier versions, and so is the preferred syntax.

Regards,

David
--
David Christensen
End Point Corporation
[email protected]