On Thu, Oct 30, 2003 at 11:13:47AM +0000 Nick Ing-Simmons wrote:
> Sisyphus <[EMAIL PROTECTED]> writes:
> >Tassilo von Parseval wrote:
> >> It is. If you have code like
> >>
> >> {
> >> my $var = my_xsub();
> >> ...
> >> }
> >>
> >> and want $var to be cleaned up when it falls out of scope, you have to
> >> make it a mortal. Mortals are just variables that clean up themselves
> >> when their reference count goes to zero.
> >>
> >
> >I still question that - and hope that in so doing I don't raise your
> >anger. (That's not what I'm trying to do :-)
>
> You are right.
>
> The sv_2mortal _IS_ needed in the
>
> void
> my_xsub()
> CODE:
> {
> ST(0) = sv_2mortal(newSVpv(string,strlen(string));
> XSRETURN(1);
> }
>
> case.
>
> But it is inserted for you SV * return case:
>
> {
> RETVAL=newSV...;
> }
> #line 25 "Foo.c"
> ST(0) = RETVAL;
> sv_2mortal(ST(0));
> }
> XSRETURN(1);
> }
Hmmh, indeed. I peeked at xsubpp and it looks as though this is a
special case:
elsif ($expr =~ /^\s*\$arg\s*=/) {
# We expect that $arg has refcnt >=1, so we need
# to mortalize it!
eval "print qq\a$expr\a";
warn $@ if $@;
print "\tsv_2mortal(ST(0));\n";
print "\tSvSETMAGIC(ST(0));\n" if $do_setmagic;
}
The typemap entry for 'SV*' expands to
$arg = $var
However, doing
char *
my_xsub()
CODE:
RETVAL = strdup(string);
OUTPUT:
RETVAL
will leak since the returned SV is not mortalized (and the copy of
'string' thus never freed).
I think this is one good reason for sticking to one style of handling
return values in XS since they differ quite significantly. I prefer the
explicit manipulation of the return stack by feeding it my manually
constructed SV's. That way, I can be sure that each scalar has the
characteristics it is supposed to have.
Tassilo
--
$_=q#",}])!JAPH!qq(tsuJ[{@"tnirp}3..0}_$;//::niam/s~=)]3[))_$-3(rellac(=_$({
pam{rekcahbus})(rekcah{lrePbus})(lreP{rehtonabus})!JAPH!qq(rehtona{tsuJbus#;
$_=reverse,s+(?<=sub).+q#q!'"qq.\t$&."'!#+sexisexiixesixeseg;y~\n~~dddd;eval
