: 0
);
sv->sv_debug_inpad = 0;
- sv->sv_debug_cloned = 0;
+ sv->sv_debug_parent = NULL;
sv->sv_debug_file = PL_curcop ? savepv(CopFILE(PL_curcop)): NULL;
sv->sv_debug_serial = PL_sv_serial++;
/* Give tsv backref magic if it hasn't already got it, then push a
* back-reference to sv onto the array associated with the backref magic.
+ *
+ * As an optimisation, if there's only one backref and it's not an AV,
+ * store it directly in the HvAUX or mg_obj slot, avoiding the need to
+ * allocate an AV. (Whether the slot holds an AV tells us whether this is
+ * active.)
+ *
+ * If an HV's backref is stored in magic, it is moved back to HvAUX.
*/
/* A discussion about the backreferences array and its refcount:
*
* The AV holding the backreferences is pointed to either as the mg_obj of
- * PERL_MAGIC_backref, or in the specific case of a HV, from the
- * xhv_backreferences field of the HvAUX structure. The array is created
- * with a refcount of 2. This means that if during global destruction the
- * array gets picked on before its parent to have its refcount decremented
- * by the random zapper, it won't actually be freed, meaning it's still
- * there for when its parent gets freed.
- * When the parent SV is freed, in the case of magic, the magic is freed,
- * Perl_magic_killbackrefs is called which decrements one refcount, then
- * mg_obj is freed which kills the second count.
- * In the vase of a HV being freed, one ref is removed by S_hfreeentries,
- * the other by Perl_sv_kill_backrefs, which it calls.
+ * PERL_MAGIC_backref, or in the specific case of a HV that has the hv_aux
+ * structure, from the xhv_backreferences field. (A HV without hv_aux will
+ * have the standard magic instead.) The array is created with a refcount
+ * of 2. This means that if during global destruction the array gets
+ * picked on before its parent to have its refcount decremented by the
+ * random zapper, it won't actually be freed, meaning it's still there for
+ * when its parent gets freed.
+ *
+ * When the parent SV is freed, the extra ref is killed by
+ * Perl_sv_kill_backrefs. The other ref is killed, in the case of magic,
+ * by mg_free() / MGf_REFCOUNTED, or for a hash, by Perl_hv_kill_backrefs.
+ *
+ * When a single backref SV is stored directly, it is not reference
+ * counted.
*/
void
Perl_sv_add_backref(pTHX_ SV *const tsv, SV *const sv)
{
dVAR;
- AV *av;
+ SV **svp;
+ AV *av = NULL;
+ MAGIC *mg = NULL;
PERL_ARGS_ASSERT_SV_ADD_BACKREF;
- if (SvTYPE(tsv) == SVt_PVHV) {
- AV **const avp = Perl_hv_backreferences_p(aTHX_ MUTABLE_HV(tsv));
+ /* find slot to store array or singleton backref */
- av = *avp;
- if (!av) {
- av = newAV();
- AvREAL_off(av);
- SvREFCNT_inc_simple_void(av); /* see discussion above */
- *avp = av;
+ if (SvTYPE(tsv) == SVt_PVHV) {
+ svp = (SV**)Perl_hv_backreferences_p(aTHX_ MUTABLE_HV(tsv));
+
+ if (!*svp) {
+ if ((mg = mg_find(tsv, PERL_MAGIC_backref))) {
+ /* Aha. They've got it stowed in magic instead.
+ * Move it back to xhv_backreferences */
+ *svp = mg->mg_obj;
+ /* Stop mg_free decreasing the reference count. */
+ mg->mg_obj = NULL;
+ /* Stop mg_free even calling the destructor, given that
+ there's no AV to free up. */
+ mg->mg_virtual = 0;
+ sv_unmagic(tsv, PERL_MAGIC_backref);
+ mg = NULL;
+ }
}
} else {
- const MAGIC *const mg
- = SvMAGICAL(tsv) ? mg_find(tsv, PERL_MAGIC_backref) : NULL;
- if (mg)
- av = MUTABLE_AV(mg->mg_obj);
- else {
- av = newAV();
- AvREAL_off(av);
- sv_magic(tsv, MUTABLE_SV(av), PERL_MAGIC_backref, NULL, 0);
- /* av now has a refcnt of 2; see discussion above */
+ if (! ((mg =
+ (SvMAGICAL(tsv) ? mg_find(tsv, PERL_MAGIC_backref) : NULL))))
+ {
+ sv_magic(tsv, NULL, PERL_MAGIC_backref, NULL, 0);
+ mg = mg_find(tsv, PERL_MAGIC_backref);
}
+ svp = &(mg->mg_obj);
}
+
+ /* create or retrieve the array */
+
+ if ( (!*svp && SvTYPE(sv) == SVt_PVAV)
+ || (*svp && SvTYPE(*svp) != SVt_PVAV)
+ ) {
+ /* create array */
+ av = newAV();
+ AvREAL_off(av);
+ SvREFCNT_inc_simple_void(av);
+ /* av now has a refcnt of 2; see discussion above */
+ if (*svp) {
+ /* move single existing backref to the array */
+ av_extend(av, 1);
+ AvARRAY(av)[++AvFILLp(av)] = *svp; /* av_push() */
+ }
+ *svp = (SV*)av;
+ if (mg)
+ mg->mg_flags |= MGf_REFCOUNTED;
+ }
+ else
+ av = MUTABLE_AV(*svp);
+
+ if (!av) {
+ /* optimisation: store single backref directly in HvAUX or mg_obj */
+ *svp = sv;
+ return;
+ }
+ /* push new backref */
+ assert(SvTYPE(av) == SVt_PVAV);
if (AvFILLp(av) >= AvMAX(av)) {
av_extend(av, AvFILLp(av)+1);
}
Perl_sv_del_backref(pTHX_ SV *const tsv, SV *const sv)
{
dVAR;
- AV *av = NULL;
- SV **svp;
+ SV **svp = NULL;
I32 i;
PERL_ARGS_ASSERT_SV_DEL_BACKREF;
- if (SvTYPE(tsv) == SVt_PVHV) {
- if (SvOOK(tsv)) {
- /* SvOOK: We must avoid creating the hv_aux structure if its
- * not already there, as that is stored in the main HvARRAY(),
- * and hfreentries assumes that no-one reallocates HvARRAY()
- * while it is running. */
- av = *Perl_hv_backreferences_p(aTHX_ MUTABLE_HV(tsv));
- }
+ if (SvTYPE(tsv) == SVt_PVHV && SvOOK(tsv)) {
+ svp = (SV**)Perl_hv_backreferences_p(aTHX_ MUTABLE_HV(tsv));
}
- else {
- const MAGIC *const mg
+ if (!svp || !*svp) {
+ MAGIC *const mg
= SvMAGICAL(tsv) ? mg_find(tsv, PERL_MAGIC_backref) : NULL;
- if (mg)
- av = MUTABLE_AV(mg->mg_obj);
+ svp = mg ? &(mg->mg_obj) : NULL;
}
- if (!av)
+ if (!svp || !*svp)
Perl_croak(aTHX_ "panic: del_backref");
- assert(!SvIS_FREED(av));
-
- svp = AvARRAY(av);
- /* We shouldn't be in here more than once, but for paranoia reasons lets
- not assume this. */
- for (i = AvFILLp(av); i >= 0; i--) {
- if (svp[i] == sv) {
- const SSize_t fill = AvFILLp(av);
- if (i != fill) {
- /* We weren't the last entry.
- An unordered list has this property that you can take the
- last element off the end to fill the hole, and it's still
- an unordered list :-)
- */
- svp[i] = svp[fill];
+ if (SvTYPE(*svp) == SVt_PVAV) {
+ int count = 0;
+ AV * const av = (AV*)*svp;
+ assert(!SvIS_FREED(av));
+ svp = AvARRAY(av);
+ for (i = AvFILLp(av); i >= 0; i--) {
+ if (svp[i] == sv) {
+ const SSize_t fill = AvFILLp(av);
+ if (i != fill) {
+ /* We weren't the last entry.
+ An unordered list has this property that you can take the
+ last element off the end to fill the hole, and it's still
+ an unordered list :-)
+ */
+ svp[i] = svp[fill];
+ }
+ svp[fill] = NULL;
+ AvFILLp(av) = fill - 1;
+ count++;
+#ifndef DEBUGGING
+ break; /* should only be one */
+#endif
}
- svp[fill] = NULL;
- AvFILLp(av) = fill - 1;
}
+ assert(count == 1);
}
+ else {
+ /* optimisation: only a single backref, stored directly */
+ if (*svp != sv)
+ Perl_croak(aTHX_ "panic: del_backref");
+ *svp = NULL;
+ }
+
}
-int
+void
Perl_sv_kill_backrefs(pTHX_ SV *const sv, AV *const av)
{
- SV **svp = AvARRAY(av);
+ SV **svp;
+ SV **last;
+ bool is_array;
PERL_ARGS_ASSERT_SV_KILL_BACKREFS;
- if (svp) {
- SV *const *const last = svp + AvFILLp(av);
+ if (!av)
+ return;
+ is_array = (SvTYPE(av) == SVt_PVAV);
+ if (is_array) {
assert(!SvIS_FREED(av));
+ svp = AvARRAY(av);
+ if (svp)
+ last = svp + AvFILLp(av);
+ }
+ else {
+ /* optimisation: only a single backref, stored directly */
+ svp = (SV**)&av;
+ last = svp;
+ }
+
+ if (svp) {
while (svp <= last) {
if (*svp) {
SV *const referrer = *svp;
(UV)SvFLAGS(referrer));
}
- *svp = NULL;
+ if (is_array)
+ *svp = NULL;
}
svp++;
}
+ }
+ if (is_array) {
AvFILLp(av) = -1;
+ SvREFCNT_dec(av); /* remove extra count added by sv_add_backref() */
}
- SvREFCNT_dec(av); /* remove extra count added by sv_add_backref() */
- return 0;
+ return;
}
/*
/* will the CV shortly be freed by gp_free() ? */
if (GvCV(gv) == cv && GvGP(gv)->gp_refcnt < 2 && SvREFCNT(cv) < 2) {
- CvGV(cv) = NULL;
+ SvANY(cv)->xcv_gv = NULL;
return;
}
CvANON_on(cv);
CvCVGV_RC_on(cv);
- CvGV(cv) = MUTABLE_GV(SvREFCNT_inc(anongv));
+ SvANY(cv)->xcv_gv = MUTABLE_GV(SvREFCNT_inc(anongv));
}
if (PL_last_swash_hv == (const HV *)sv) {
PL_last_swash_hv = NULL;
}
+ Perl_hv_kill_backrefs(aTHX_ MUTABLE_HV(sv));
hv_undef(MUTABLE_HV(sv));
break;
case SVt_PVAV:
}
else
*/
- if(nmg->mg_type == PERL_MAGIC_backref) {
- /* The backref AV has its reference count deliberately bumped by
- 1. */
- nmg->mg_obj
- = SvREFCNT_inc(av_dup_inc((const AV *) nmg->mg_obj, param));
- }
- else {
- nmg->mg_obj = (nmg->mg_flags & MGf_REFCOUNTED)
- ? sv_dup_inc(nmg->mg_obj, param)
- : sv_dup(nmg->mg_obj, param);
- }
+ nmg->mg_obj = (nmg->mg_flags & MGf_REFCOUNTED)
+ ? nmg->mg_type == PERL_MAGIC_backref
+ /* The backref AV has its reference
+ * count deliberately bumped by 1 */
+ ? SvREFCNT_inc(av_dup_inc((const AV *)
+ nmg->mg_obj, param))
+ : sv_dup_inc(nmg->mg_obj, param)
+ : sv_dup(nmg->mg_obj, param);
if (nmg->mg_ptr && nmg->mg_type != PERL_MAGIC_regex_global) {
if (nmg->mg_len > 0) {
dstr->sv_debug_optype = sstr->sv_debug_optype;
dstr->sv_debug_line = sstr->sv_debug_line;
dstr->sv_debug_inpad = sstr->sv_debug_inpad;
- dstr->sv_debug_cloned = 1;
+ dstr->sv_debug_parent = (SV*)sstr;
dstr->sv_debug_file = savepv(sstr->sv_debug_file);
#endif
* thread */
? NULL
: saux->xhv_backreferences
- ? MUTABLE_AV(SvREFCNT_inc(
- sv_dup_inc((const SV *)saux->xhv_backreferences, param)))
+ ? (SvTYPE(saux->xhv_backreferences) == SVt_PVAV)
+ ? MUTABLE_AV(SvREFCNT_inc(
+ sv_dup_inc((const SV *)
+ saux->xhv_backreferences, param)))
+ : MUTABLE_AV(sv_dup((const SV *)
+ saux->xhv_backreferences, param))
: 0;
daux->xhv_mro_meta = saux->xhv_mro_meta
}
/* don't dup if copying back - CvGV isn't refcounted, so the
* duped GV may never be freed. A bit of a hack! DAPM */
- CvGV(dstr) =
+ SvANY(MUTABLE_CV(dstr))->xcv_gv =
CvCVGV_RC(dstr)
? gv_dup_inc(CvGV(sstr), param)
: (param->flags & CLONEf_JOIN_IN)
/* switches */
PL_minus_c = proto_perl->Iminus_c;
PL_patchlevel = sv_dup_inc(proto_perl->Ipatchlevel, param);
+ PL_apiversion = sv_dup_inc(proto_perl->Iapiversion, param);
PL_localpatches = proto_perl->Ilocalpatches;
PL_splitstr = proto_perl->Isplitstr;
PL_minus_n = proto_perl->Iminus_n;
https://perl5.git.perl.org / perl5.git / blobdiff