Minimum Perl version?

Minimum Perl version?

[Tait]

What is the minimum Perl version git expects to support?

I ask, because f922df8... seems to have introduced a open() syntax that
is not compatible with some older Perl versions.

Re: Minimum Perl version?

[Ævar Arnfjörð Bjarmason]

On Fri, Sep 24, 2010 at 10:00, Tait <git.git@t41t.com> wrote:
>
> What is the minimum Perl version git expects to support?
>
> I ask, because f922df8... seems to have introduced a open() syntax that
> is not compatible with some older Perl versions.

We generally support 5.6 or above, but 5.8 or above for some other
programs.

As far as I can tell there was no new open syntax introduced in that
series that wasn't supported before.

What specifically is breaking for you, and on what perl version?

Re: Minimum Perl version?

[Tor Arntsen]

On Fri, Sep 24, 2010 at 12:00, Tait <git.git@t41t.com> wrote:
>
> What is the minimum Perl version git expects to support?
>
> I ask, because f922df8... seems to have introduced a open() syntax that
> is not compatible with some older Perl versions.

I've found that for add -p you'll need 5.8.x or newer, due to stuff like

                my $fh = undef;
                open($fh, '-|', @_) or die;

which fails in e.g. perl 5.6.
There could be some other stuff (in addition to add -p) that also does
this kind of thing.

-Tor

Re: Minimum Perl version?

[Ævar Arnfjörð Bjarmason]

On Fri, Sep 24, 2010 at 10:27, Tor Arntsen <tor@spacetec.no> wrote:
> On Fri, Sep 24, 2010 at 12:00, Tait <git.git@t41t.com> wrote:
>>
>> What is the minimum Perl version git expects to support?
>>
>> I ask, because f922df8... seems to have introduced a open() syntax that
>> is not compatible with some older Perl versions.
>
> I've found that for add -p you'll need 5.8.x or newer, due to stuff like
>
>                my $fh = undef;
>                open($fh, '-|', @_) or die;
>
> which fails in e.g. perl 5.6.
> There could be some other stuff (in addition to add -p) that also does
> this kind of thing.

If that's the case (I don't have a 5.6 here to do archeology on) then
git add -p never worked in 5.6. That was added in 5cde71d6 when it was
introduced in 2006:

    +sub run_cmd_pipe {
    +       my $fh = undef;
    +       open($fh, '-|', @_) or die;
    +       return <$fh>;
    +}

Can you show us the specific error you're getting, and the output of
your `perl -V` ?

Re: Minimum Perl version?

[Tor Arntsen]

On Fri, Sep 24, 2010 at 13:05, Ævar Arnfjörð Bjarmason <avarab@gmail.com> wrote:
> On Fri, Sep 24, 2010 at 10:27, Tor Arntsen <tor@spacetec.no> wrote:
[..]
>> I've found that for add -p you'll need 5.8.x or newer, due to stuff like
>>
>>                my $fh = undef;
>>                open($fh, '-|', @_) or die;
>>
>> which fails in e.g. perl 5.6.
>> There could be some other stuff (in addition to add -p) that also does
>> this kind of thing.
>
> If that's the case (I don't have a 5.6 here to do archeology on) then
> git add -p never worked in 5.6. That was added in 5cde71d6 when it was
> introduced in 2006:
>
>    +sub run_cmd_pipe {
>    +       my $fh = undef;
>    +       open($fh, '-|', @_) or die;
>    +       return <$fh>;
>    +}
>
> Can you show us the specific error you're getting, and the output of
> your `perl -V` ?

I don't have that particular installation anymore (I installed perl
5.8 on the machine I had trouble with), and the only other system I
have left with perl 5.6 only has an old Git 1.5 version. But it's easy
enough to reproduce, Perl 5.6 simply doesn't support that notation.
Put the code above in a perl script and execute it:

Can't use an undefined value as filehandle reference at test-pl.pl line 5.
(that's the 'open' line)

I can provide the output of -V if you wish, but I don't think it
matters really, except for the version:

"Summary of my perl5 (revision 5.0 version 6 subversion 1) configuration:"..
I.e. perl 5.6.1. The above is from Irix, the original installation I
ran Git on was AIX with Perl 5.6.1.

-Tor

Re: Minimum Perl version?

[Alex Riesen]

On Fri, Sep 24, 2010 at 13:22, Tor Arntsen <tor@spacetec.no> wrote:
>> If that's the case (I don't have a 5.6 here to do archeology on) then
>> git add -p never worked in 5.6. That was added in 5cde71d6 when it was
>> introduced in 2006:
>>
>>    +sub run_cmd_pipe {
>>    +       my $fh = undef;
>>    +       open($fh, '-|', @_) or die;
>>    +       return <$fh>;
>>    +}
>>
>
> Can't use an undefined value as filehandle reference at test-pl.pl line 5.
> (that's the 'open' line)

Maybe it is not the syntax (the separate argument for open mode
in this case), but the initialization of $fh to 'undef' which is the
problem here?

Re: Minimum Perl version?

[Tor Arntsen]

On Fri, Sep 24, 2010 at 14:30, Alex Riesen <raa.lkml@gmail.com> wrote:

> Maybe it is not the syntax (the separate argument for open mode
> in this case), but the initialization of $fh to 'undef' which is the
> problem here?

That's correct, I believe, but I also think the underlying problem here
is having support for dynamic filehandles which can be exported.
You could assign something to $fh and then call open(), but that
won't give you what the code asks for.

It should in principle be possible to replace
 my $fh = undef;
 open ($fh..)
with
 use FileHandle;
 my $fh = new FileHandle (...)
etc.
which works also on Perl 5.6.

When I first ran into this I did a little bit of hacking in that
direction, but I didn't make a full effort and didn't get it to work -
in the meantime the customer system which required perl 5.6 (for
performance reasons) migrated to a later version of AIX and I was then
free to upgrade the perl version to 5.8 on this (my maintance copy of
their system), in other words I wasn't affected by the problem anymore
and abandoned what I had started working on.

-Tor

Re: Minimum Perl version?

[Tait]

> > What is the minimum Perl version git expects to support?
> >
> > I ask, because f922df8... seems to have introduced a open() syntax that
> > is not compatible with some older Perl versions.
>
> We generally support 5.6 or above, but 5.8 or above for some other
> programs.

I am having to use a system with 5.6.1 to do cvsimport and cvsexportcommit,
and interactive add. I haven't tried sendmail or other functions, yet. This
system was previously using git 1.6.5.something, and did not have these
problems as of that release, but now that I'm building git 1.7.3, they
have appeared.

Perl 5.6.1 doesn't support the list open syntax, so one must replace
open(my $fh, '-|', @list) with open(my $fh, '-|'), and then exec(@list).
I'm working up a patch set to fill my own needs on this system, but based
on the subsequent discussion about setting 5.8 as the minimum, it sounds
like it's not worth submitting.

Thanks.

Re: Minimum Perl version?

[Ævar Arnfjörð Bjarmason]

On Fri, Sep 24, 2010 at 20:40, Tait <git.git@t41t.com> wrote:
>> > What is the minimum Perl version git expects to support?
>> >
>> > I ask, because f922df8... seems to have introduced a open() syntax that
>> > is not compatible with some older Perl versions.
>>
>> We generally support 5.6 or above, but 5.8 or above for some other
>> programs.
>
> I am having to use a system with 5.6.1 to do cvsimport and cvsexportcommit,
> and interactive add. I haven't tried sendmail or other functions, yet. This
> system was previously using git 1.6.5.something, and did not have these
> problems as of that release, but now that I'm building git 1.7.3, they
> have appeared.

Maybe marking everything as needing 5.8 or later isn't the right thing
to do. E.g. the git-*cvs*.perl code mostly isn't touched, but
cvsexportcommit does use Git.pm, so that would also need to be pinned
at 5.6 if cvsexportcommit was.

> Perl 5.6.1 doesn't support the list open syntax, so one must replace
> open(my $fh, '-|', @list) with open(my $fh, '-|'), and then exec(@list).
> I'm working up a patch set to fill my own needs on this system, but based
> on the subsequent discussion about setting 5.8 as the minimum, it sounds
> like it's not worth submitting.

The issue isn't that we don't have a workaround for individual bits
like open(my $fh, '-|', @list), but rather that keeping all of the
code 5.6 compatible is a burden on ongoing maintenance for a very
marginal benefit.

Re: Minimum Perl version?

[Andreas Ericsson]

On 09/25/2010 12:39 AM, Ævar Arnfjörð Bjarmason wrote:
> On Fri, Sep 24, 2010 at 20:40, Tait<git.git@t41t.com>  wrote:
>>>> What is the minimum Perl version git expects to support?
>>>>
>>>> I ask, because f922df8... seems to have introduced a open() syntax that
>>>> is not compatible with some older Perl versions.
>>>
>>> We generally support 5.6 or above, but 5.8 or above for some other
>>> programs.
>>
>> I am having to use a system with 5.6.1 to do cvsimport and cvsexportcommit,
>> and interactive add. I haven't tried sendmail or other functions, yet. This
>> system was previously using git 1.6.5.something, and did not have these
>> problems as of that release, but now that I'm building git 1.7.3, they
>> have appeared.
> 
> Maybe marking everything as needing 5.8 or later isn't the right thing
> to do. E.g. the git-*cvs*.perl code mostly isn't touched, but
> cvsexportcommit does use Git.pm, so that would also need to be pinned
> at 5.6 if cvsexportcommit was.
> 
>> Perl 5.6.1 doesn't support the list open syntax, so one must replace
>> open(my $fh, '-|', @list) with open(my $fh, '-|'), and then exec(@list).
>> I'm working up a patch set to fill my own needs on this system, but based
>> on the subsequent discussion about setting 5.8 as the minimum, it sounds
>> like it's not worth submitting.
> 
> The issue isn't that we don't have a workaround for individual bits
> like open(my $fh, '-|', @list), but rather that keeping all of the
> code 5.6 compatible is a burden on ongoing maintenance for a very
> marginal benefit.

If someone steps up and makes various snippets of code 5.6 compatible while
not introducing any penalties for 5.8 users, I see no reason to drop those
patches.

Tait, submit your patches and I'm sure they'll be reviewed the same as
everything else. If they make the code a lot harder to understand or a lot
slower, I'm sure they'll be dropped. If they don't, I'm reasonably certain
Junio will take them on. I barely speak Perl though, so reviewing them will
have to be done by someone else.

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231

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