diff options
Diffstat (limited to 'hv.c')
| -rw-r--r-- | hv.c | 22 |
1 files changed, 15 insertions, 7 deletions
@@ -1666,15 +1666,23 @@ S_hfreeentries(pTHX_ HV *hv) HE *entry; struct mro_meta *meta; struct xpvhv_aux *iter = HvAUX(hv); - /* If there are weak references to this HV, we need to avoid - freeing them up here. In particular we need to keep the AV - visible as what we're deleting might well have weak references - back to this HV, so the for loop below may well trigger - the removal of backreferences from this array. */ + /* weak references: if called from sv_clear(), the backrefs + * should already have been killed; if there are any left, its + * because we're doing hv_clear() or hv_undef(), and the HV + * will continue to live. + * Because while freeing the entries we fake up a NULL HvARRAY + * (and hence HvAUX), we need to store the backref array + * somewhere else; but it still needs to be visible in case + * any the things we free happen to call sv_del_backref(). + * We do this by storing it in magic instead. + * If, during the entry freeing, a destructor happens to add + * a new weak backref, then sv_add_backref will look in both + * places (magic in HvAUX) for the AV, but will create a new + * AV in HvAUX if it can't find one. So at the end of the + * iteration we have to allow for this. */ if (iter->xhv_backreferences) { - /* So donate them to regular backref magic to keep them safe. - The sv_magic will increase the reference count of the AV, + /* The sv_magic will increase the reference count of the AV, so we need to drop it first. */ SvREFCNT_dec(iter->xhv_backreferences); if (AvFILLp(iter->xhv_backreferences) == -1) { |