Bug #36087 for Storable: segfaults when called during global destruction

> <URL: https://rt.cpan.org/Ticket/Display.html?id=36087 > > > The testcase, for reference: > >    #!/usr/bin/perl > >    use strict; >    use warnings; > >    our $a = new Foo(); >    $a->{bar} = "baz"; > >    package Foo; >    use Storable; > >    sub new { >    return bless({}, "Foo"); >    } >    sub DESTROY { >    my $this = shift; >    warn "Destroying $this, bar=$this->{bar}"; >    my $f = Storable::freeze($this); >    } > > Here's a workaround that Git instated due to this issue: > http://github.com/git/git/commit/8ac3a667 > > I investigated it a bit, it's segfaulting at the very start of > do_store(): > >    here  ==> dSTCXT; >                  int status; > > When I manually expand that macro it ends up being: > >    { >        SV *perinterp_sv = *hv_fetch(PL_modglobal, >                                     MY_VERSION, sizeof(MY_VERSION)-1, > TRUE); >        stcxt_t * cxt; >        if (perinterp_sv && SvIOK(perinterp_sv) && SvIVX(perinterp_sv)) > { >            IV x = SvIVX(perinterp_sv); >            void* ptr = INT2PTR(SV*,x); >            SV* rv = SvRV(ptr); >    =>      cxt = (stcxt_t *)SvPVX(rv); >        } else { >            cxt = (stcxt_t *) 0; >        } >        int status; > > ptr is an OK scalar, but its RV slot is NULL. Even if that call hadn't > failed and cxt was set to 0 it would still segfault later in the > function, e.g. here: > >    if (cxt->s_dirty) >        clean_context(aTHX_ cxt); > > The problem is seemingly that Storable is looking at its own context > during global destruction, but when it gets around to it perl has > already started freeing the variables that it depends on. > > Looking at anything during global destruction is dangerous. Storable > should either be fixed to hook into destruction earlier, or this > limitation documented. Maybe there's also a workaround I haven't > spotted.