Re: PL/Perl Does not Like vstrings

On 01/04/2012 11:15 AM, Tom Lane wrote:
> Andrew Dunstan<andrew(at)dunslane(dot)net> writes:
>> On 01/04/2012 12:47 AM, David E. Wheeler wrote:
>>> Oy, this doesn’t look good:
>>> $ do LANGUAGE plperl $$ elog(NOTICE, $^V) $$;
>>> The connection to the server was lost. Attempting reset: Succeeded.
>> Try
>> elog(NOTICE, "$^V")
> Isn't this a Perl bug? It seems to be crashing in SvPVutf8, which
> means that either Perl passed something that's not an SV to a function
> declared to accept SVs, or that SvPVutf8 fails on some SVs. Either
> way, Perl is failing to satisfy the POLA if you ask me.

Ummmm, not sure.

The docs (perldoc perlvar) seem to suggest $^V isn't an SV (i.e. a
scalar) but some other sort of animal:

$^V The revision, version, and subversion of the Perl interpreter,
represented as a "version" object.

This variable first appeared in perl 5.6.0; earlier versions of
perl will see an undefined value. Before perl 5.10.0 $^V was
represented as a v-string.

$^V can be used to determine whether the Perl interpreter
executing a script is in the right range of versions. For
example:

warn "Hashes not randomized!\n" if !$^V or $^V lt v5.8.1

To convert $^V into its string representation use "sprintf()"'s
"%vd" conversion:

printf "version is v%vd\n", $^V; # Perl's version

But Util.xs::util_elog() expects an SV and doesn't check whether or not
it actually has one. I've found a few other ways of crashing this call
(e.g. by passing a typeglob), so maybe we need to test that we actually
have an SV. I think SvOK() is what we'd use for that - perl gurus please
confirm.

cheers

andrew