Hi Brad,
FYI, the problem is in the "orassign" (||=) implementation, it breaks
if you take the left hand side expression "away" while evaluating the
right hand side. In this case, the problem lies in sock_to_host doing
a @buck2sock = (). The ||= will have some kind of pointer on
$buck2sock[$bucket] before calling sock_to_host, which will delete
it. And perl ends up copying some random crap into an SV, and it
(usually) breaks a bit later. Perl 5.9.4 at least recognizes it's
doing something bad, but still doesn't do the right thing.
Got lost in the perl source, so can't yet provide a fix :-( I can
provide a good test case, though:
my @array;
sub fn
{
@array = ();
}
$array[0] = 1;
my $var = $array[1] ||= fn();
Jacques.
At 00:00 03/07/2007, Brad Fitzpatrick wrote:
Crazy.
Patch applied. I'll try to contact Perl people who can look into this bug
in Perl.
- Brad
On Thu, 28 Jun 2007, Matthieu PATOU wrote:
> Dear list
> the current version (1.23 from SVN) of the memcached perl client
crash when it once fail to connect an host and the
> success to connect to another host.
>
> On my workstation (Linux ubuntu 6.10), when the problem occurs i get :
>
> [EMAIL PROTECTED]:~/work/memcached-ref/api/perl$ perl mctest.pl
> using parser: Cache::Memcached::GetParser
> *** glibc detected *** perl: munmap_chunk(): invalid pointer:
0x081fd690 ***
> ======= Backtrace: =========
> /lib/tls/i686/cmov/libc.so.6(__libc_free+0x18a)[0xb7e02b4a]
> perl(Perl_sv_setsv_flags+0x5cb)[0x80d370f]
> perl(Perl_pp_sassign+0x56)[0x80c37e4]
> perl(Perl_runops_standard+0x13)[0x80bb273]
> perl(perl_run+0x2e1)[0x80639b4]
> perl(main+0x112)[0x8060012]
> /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xdc)[0xb7db18cc]
> perl[0x805fe81]
> ======= Memory map: ========
>
>
> The GetParserXS module is NOT installed
> After some sessions of debugging it appears that it is Perl which
fools itself when executing :
> $sock = $buck2sock[$bucket] ||=
$self->sock_to_host($self->{buckets}[ $bucket ]
>
> When sock_to_host had returned undef (because it had been unable
to connect to the desired server), the next execution
> of this line will crash when trying to set the return value of
sock_to_host into $buck2sock[$bucket]
>
> The test case is in the mctest.pl (I simulate the timeout on
connect by NOT having a memcache server listening on 11212).
>
> I fix the bug by simplifying the code and splitting into smaller
pieces (see the patch attached to this mail).
>
> Cheers
> Matthieu
>
>
>
