patcht9700-perl-git.sh: Fix a test failure on cygwin

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
---

This patch fixes the t9700 test failure on cygwin. Don't ask me to explain why the original test.pl fails on cygwin, but passes on Linux!

My perl version:

    $ perl --version

    This is perl, v5.8.7 built for cygwin-thread-multi-64int
    (with 1 registered patch, see perl -V for more detail)

    Copyright 1987-2005, Larry Wall

    Perl may be copied only under the terms of either the Artistic License or the
    GNU General Public License, which may be found in the Perl 5 source kit.

    Complete documentation for Perl, including FAQ lists, should be found on
    this system using `man perl' or `perldoc perl'.  If you have access to the
    Internet, point your browser at http://www.perl.org/, the Perl Home Page.
    $ 

[My perl version on Linux is whatever comes with Ubuntu 7.04]

ATB,

Ramsay Jones

 t/t9700/test.pl |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

Ramsay Jones <ramsay@ramsay1.demon.co.uk> writes:

Curious.

What does this give you:

	$ cd t
        $ sh t9700-perl-git.sh -v

with the attached patch? Unfortunately this cannot be run with "-i -v" because 'test_external_without_stderr' uses test_external which in turn exits upon failure when -i is given, without letting the former to report what was given to the standard error stream (this is slightly offtopic but pertains to debuggability of tests, so Lea is Cc'ed).

For me, cwd() is the same as Cwd->cwd (this is from Perl 5.8.8); perhaps it behaves differently on Cygwin?

 t/t9700/test.pl |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

Junio C Hamano wrote:

[snip]

Yes, sorry, I should have spent a few minutes explaining the cause of the bug and why the patch fixes it; my bad!

(I was in a bit of a hurry; I had just re-booted twice in quick succession, once into Linux so that I could pull the patch over to test it there, before going back to Windows, in order to format-patch and send it to the ML. Yes it is a PITA 8-)

I haven't tried your patch because, well, I already know what it will say!

Once I determined that the problem must be in the following four lines of the t/t9700/test.pl script:

17 our $repo_dir = "trash directory"; 18 our $abs_repo_dir = Cwd->cwd; 19 die "this must be run by calling the t/t97* shell script(s)\n" 20 if basename(Cwd->cwd) ne $repo_dir;

then the problem and the solution was immediately obvious. Well, maybe that is overstating it slightly. After all, I still indulged in a spot of "printf debugging" just to make sure! I'm sure you can imagine what it looked like ;-) [BTW, the reason it was obvious, is that I have met this problem *too many* times in the past, so I'm "attuned" to it. Don't worry, I will dispense with the rant this time :-P]

I won't repeat that here, but offer a quick script:

    $ cat test-cwd.pl
    use Cwd;

    print "cwd():      ", cwd(),      "\n";
    print "Cwd::cwd(): ", Cwd::cwd(), "\n";
    print "Cwd->cwd:   ", Cwd->cwd,   "\n";
    $
on cygwin:
    $ perl test-cwd.pl
    cwd():      /home/ramsay
    Cwd::cwd(): /home/ramsay
    Usage: Cwd::cwd() at test-cwd.pl line 5.
    $
and on Linux:
    $ perl test-cwd.pl
    cwd():      /home/ramsay
    Cwd::cwd(): /home/ramsay
    Cwd->cwd:   /home/ramsay
    $

So it is clear, the problem is caused by the "method invocation syntax". Among other things, this mechanism auto-magically inserts a new (in this case only) first parameter which represents the "class" Cwd to the cwd() "method-call".

So, do a "perldoc Cwd" and take a look at the example usage. So is cwd() a method of the Cwd class, or is it a function in the Cwd namespace? Exactly, hence the patch. (Well, some may prefer to see the Cwd::cwd() syntax used instead. Dunno)

So, the bug is inappropriate use of the method invocation syntax. But that didn't explain the difference in behaviour on the two platforms, hence my "Don't ask me to explain ..." comment.

Now it just so happens that I have the source code to perl v5.8.8 in my home directory (no really!) on Linux, so I spent a little time rooting around to try and explain it.

The changelog type files, perl-5.8.8/Changes and perl-5.8.8/ext/Cwd/Changes didn't show much of interest. The module impl. in perl-5.8.8/lib/Cwd.pm was an interesting read but didn't explain it. Then I bumped into the cygwin specific file perl-5.8.8/cygwin/cygwin.c, part of which I include below:

---perl-5.8.8/cygwin/cygwin.c:139-157---
/* see also Cwd.pm */
static
XS(Cygwin_cwd)
{
    dXSARGS;
    char *cwd;

    if(items != 0)
	Perl_croak(aTHX_ "Usage: Cwd::cwd()");
    if((cwd = getcwd(NULL, -1))) {
	ST(0) = sv_2mortal(newSVpv(cwd, 0));
	free(cwd);
#ifndef INCOMPLETE_TAINTS
	SvTAINTED_on(ST(0));
#endif
	XSRETURN(1);
    }
    XSRETURN_UNDEF;
}
------

So, that explains it.

ATB,

Ramsay Jones

P.S. I'm sure someone will say that "the real bug here" is that the cygwin platform should support the method invocation syntax just like all the other platforms. Well, I guess I don't really care that much. But If you were to push me, I would tend to go the other way, and say the other platforms should not allow an incorrect invocation to go unnoticed! Whatever.