Store the xhv_aux structure after the main array.

This reduces the size of HV bodies from 24 to 20 bytes on a 32 bit
build. It has the side effect of defined %symbol_table:: now always
being true. defined %hash is already deprecated.

p4raw-id: //depot/perl@24660

5 files changed, 131 insertions, 93 deletions

diff --git a/hv.c b/hv.c
index 521d1ff137..cfb3812ae3 100644
--- a/hv.c
+++ b/hv.c
@@ -1067,8 +1067,7 @@ S_hv_delete_common(pTHX_ HV *hv, SV *keysv, const char *key, STRLEN klen,
 	    if(!*first_entry) {
 		xhv->xhv_fill--; /* HvFILL(hv)-- */
 	    }
-	    if (xhv->xhv_aux && entry
-		== ((struct xpvhv_aux *)xhv->xhv_aux)->xhv_eiter /* HvEITER(hv) */)
+	    if (SvOOK(hv) && entry == HvAUX(hv)->xhv_eiter /* HvEITER(hv) */)
 		HvLAZYDEL_on(hv);
 	    else
 		hv_free_ent(hv, entry);
@@ -1115,21 +1114,30 @@ S_hsplit(pTHX_ HV *hv)
 	       
     PL_nomemok = TRUE;
 #if defined(STRANGE_MALLOC) || defined(MYMALLOC)
-    Renew(a, PERL_HV_ARRAY_ALLOC_BYTES(newsize), char);
+    Renew(a, PERL_HV_ARRAY_ALLOC_BYTES(newsize)
+	  + (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0), char);
     if (!a) {
       PL_nomemok = FALSE;
       return;
     }
+    if (SvOOK(hv)) {
+	Copy(HvAUX(hv), &a[newsize * sizeof(HE*)], 1, struct xpvhv_aux);
+    }
 #else
-    New(2, a, PERL_HV_ARRAY_ALLOC_BYTES(newsize), char);
+    New(2, a, PERL_HV_ARRAY_ALLOC_BYTES(newsize)
+	+ (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0), char);
     if (!a) {
       PL_nomemok = FALSE;
       return;
     }
     Copy(HvARRAY(hv), a, oldsize * sizeof(HE*), char);
+    if (SvOOK(hv)) {
+	Copy(HvAUX(hv), &a[newsize * sizeof(HE*)], 1, struct xpvhv_aux);
+    }
     if (oldsize >= 64) {
 	offer_nice_chunk(HvARRAY(hv),
-			PERL_HV_ARRAY_ALLOC_BYTES(oldsize));
+			 PERL_HV_ARRAY_ALLOC_BYTES(oldsize)
+			 + (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0));
     }
     else
 	Safefree(HvARRAY(hv));
@@ -1194,7 +1202,12 @@ S_hsplit(pTHX_ HV *hv)
       longest_chain, HvTOTALKEYS(hv), HvFILL(hv),  1+HvMAX(hv));*/
 
     ++newsize;
-    Newz(2, a, PERL_HV_ARRAY_ALLOC_BYTES(newsize), char);
+    Newz(2, a, PERL_HV_ARRAY_ALLOC_BYTES(newsize)
+	 + (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0), char);
+    if (SvOOK(hv)) {
+	Copy(HvAUX(hv), &a[newsize * sizeof(HE*)], 1, struct xpvhv_aux);
+    }
+
     was_shared = HvSHAREKEYS(hv);
 
     xhv->xhv_fill = 0;
@@ -1271,21 +1284,30 @@ Perl_hv_ksplit(pTHX_ HV *hv, IV newmax)
     if (a) {
 	PL_nomemok = TRUE;
 #if defined(STRANGE_MALLOC) || defined(MYMALLOC)
-	Renew(a, PERL_HV_ARRAY_ALLOC_BYTES(newsize), char);
+	Renew(a, PERL_HV_ARRAY_ALLOC_BYTES(newsize)
+	      + (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0), char);
 	if (!a) {
 	  PL_nomemok = FALSE;
 	  return;
 	}
+	if (SvOOK(hv)) {
+	    Copy(HvAUX(hv), &a[newsize * sizeof(HE*)], 1, struct xpvhv_aux);
+	}
 #else
-	New(2, a, PERL_HV_ARRAY_ALLOC_BYTES(newsize), char);
+	New(2, a, PERL_HV_ARRAY_ALLOC_BYTES(newsize)
+	    + (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0), char);
 	if (!a) {
 	  PL_nomemok = FALSE;
 	  return;
 	}
 	Copy(HvARRAY(hv), a, oldsize * sizeof(HE*), char);
+	if (SvOOK(hv)) {
+	    Copy(HvAUX(hv), &a[newsize * sizeof(HE*)], 1, struct xpvhv_aux);
+	}
 	if (oldsize >= 64) {
 	    offer_nice_chunk(HvARRAY(hv),
-			    PERL_HV_ARRAY_ALLOC_BYTES(oldsize));
+			     PERL_HV_ARRAY_ALLOC_BYTES(oldsize)
+			     + (SvOOK(hv) ? sizeof(struct xpvhv_aux) : 0));
 	}
 	else
 	    Safefree(HvARRAY(hv));
@@ -1348,7 +1370,6 @@ Perl_newHV(pTHX)
 
     xhv->xhv_max    = 7;	/* HvMAX(hv) = 7 (start with 8 buckets) */
     xhv->xhv_fill   = 0;	/* HvFILL(hv) = 0 */
-    xhv->xhv_aux = 0;
     return hv;
 }
 
@@ -1526,7 +1547,7 @@ Perl_hv_clear(pTHX_ HV *hv)
     HvHASKFLAGS_off(hv);
     HvREHASH_off(hv);
     reset:
-    if (xhv->xhv_aux) {
+    if (SvOOK(hv)) {
 	HvEITER_set(hv, NULL);
     }
 }
@@ -1601,18 +1622,21 @@ S_hfreeentries(pTHX_ HV *hv)
     I32 riter;
     I32 max;
     struct xpvhv_aux *iter;
-
     if (!hv)
 	return;
     if (!HvARRAY(hv))
 	return;
 
+    iter =  SvOOK(hv) ? HvAUX(hv) : 0;
+
     riter = 0;
     max = HvMAX(hv);
     array = HvARRAY(hv);
     /* make everyone else think the array is empty, so that the destructors
      * called for freed entries can't recusively mess with us */
     HvARRAY(hv) = Null(HE**); 
+    SvFLAGS(hv) &= ~SVf_OOK;
+
     HvFILL(hv) = 0;
     ((XPVHV*) SvANY(hv))->xhv_keys = 0;
 
@@ -1629,20 +1653,35 @@ S_hfreeentries(pTHX_ HV *hv)
 	    entry = array[riter];
 	}
     }
-    HvARRAY(hv) = array;
 
-    iter = ((XPVHV*) SvANY(hv))->xhv_aux;
+    if (SvOOK(hv)) {
+	/* Someone attempted to iterate or set the hash name while we had
+	   the array set to 0.  */
+	assert(HvARRAY(hv));
+
+	if (HvAUX(hv)->xhv_name)
+	    unshare_hek_or_pvn(HvAUX(hv)->xhv_name, 0, 0, 0);
+	/* SvOOK_off calls sv_backoff, which isn't correct.  */
+
+	Safefree(HvARRAY(hv));
+	HvARRAY(hv) = 0;
+	SvFLAGS(hv) &= ~SVf_OOK;
+    }
+
+    /* FIXME - things will still go horribly wrong (or at least leak) if
+       people attempt to add elements to the hash while we're undef()ing it  */
     if (iter) {
 	entry = iter->xhv_eiter; /* HvEITER(hv) */
 	if (entry && HvLAZYDEL(hv)) {	/* was deleted earlier? */
 	    HvLAZYDEL_off(hv);
 	    hv_free_ent(hv, entry);
 	}
-	if (iter->xhv_name)
-	    unshare_hek_or_pvn(iter->xhv_name, 0, 0, 0);
-	Safefree(iter);
-	((XPVHV*) SvANY(hv))->xhv_aux = 0;
+	iter->xhv_riter = -1; 	/* HvRITER(hv) = -1 */
+	iter->xhv_eiter = Null(HE*); /* HvEITER(hv) = Null(HE*) */
+	SvFLAGS(hv) |= SVf_OOK;
     }
+
+    HvARRAY(hv) = array;
 }
 
 /*
@@ -1663,12 +1702,13 @@ Perl_hv_undef(pTHX_ HV *hv)
     DEBUG_A(Perl_hv_assert(aTHX_ hv));
     xhv = (XPVHV*)SvANY(hv);
     hfreeentries(hv);
-    Safefree(HvARRAY(hv));
     if ((name = HvNAME_get(hv))) {
         if(PL_stashcache)
 	    hv_delete(PL_stashcache, name, HvNAMELEN_get(hv), G_DISCARD);
 	Perl_hv_name_set(aTHX_ hv, 0, 0, 0);
     }
+    SvFLAGS(hv) &= ~SVf_OOK;
+    Safefree(HvARRAY(hv));
     xhv->xhv_max   = 7;	/* HvMAX(hv) = 7 (it's a normal hash) */
     HvARRAY(hv) = 0;
     HvPLACEHOLDERS_set(hv, 0);
@@ -1678,10 +1718,22 @@ Perl_hv_undef(pTHX_ HV *hv)
 }
 
 struct xpvhv_aux*
-S_hv_auxinit(pTHX) {
+S_hv_auxinit(pTHX_ HV *hv) {
     struct xpvhv_aux *iter;
+    char *array;
 
-    New(0, iter, 1, struct xpvhv_aux);
+    if (!HvARRAY(hv)) {
+	Newz(0, array, PERL_HV_ARRAY_ALLOC_BYTES(HvMAX(hv) + 1)
+	    + sizeof(struct xpvhv_aux), char);
+    } else {
+	array = (char *) HvARRAY(hv);
+	Renew(array, PERL_HV_ARRAY_ALLOC_BYTES(HvMAX(hv) + 1)
+	      + sizeof(struct xpvhv_aux), char);
+    }
+    HvARRAY(hv) = (HE**) array;
+    /* SvOOK_on(hv) attacks the IV flags.  */
+    SvFLAGS(hv) |= SVf_OOK;
+    iter = HvAUX(hv);
 
     iter->xhv_riter = -1; 	/* HvRITER(hv) = -1 */
     iter->xhv_eiter = Null(HE*); /* HvEITER(hv) = Null(HE*) */
@@ -1710,14 +1762,13 @@ Perl_hv_iterinit(pTHX_ HV *hv)
 {
     register XPVHV* xhv;
     HE *entry;
-    struct xpvhv_aux *iter;
 
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
     xhv = (XPVHV*)SvANY(hv);
 
-    iter = xhv->xhv_aux;
-    if (iter) {
+    if (SvOOK(hv)) {
+	struct xpvhv_aux *iter = HvAUX(hv);
 	entry = iter->xhv_eiter; /* HvEITER(hv) */
 	if (entry && HvLAZYDEL(hv)) {	/* was deleted earlier? */
 	    HvLAZYDEL_off(hv);
@@ -1726,7 +1777,7 @@ Perl_hv_iterinit(pTHX_ HV *hv)
 	iter->xhv_riter = -1; 	/* HvRITER(hv) = -1 */
 	iter->xhv_eiter = Null(HE*); /* HvEITER(hv) = Null(HE*) */
     } else {
-	xhv->xhv_aux = S_hv_auxinit(aTHX);
+	S_hv_auxinit(aTHX_ hv);
     }
 
     /* used to be xhv->xhv_fill before 5.004_65 */
@@ -1740,10 +1791,7 @@ Perl_hv_riter_p(pTHX_ HV *hv) {
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
 
-    iter = ((XPVHV *)SvANY(hv))->xhv_aux;
-    if (!iter) {
-	((XPVHV *)SvANY(hv))->xhv_aux = iter = S_hv_auxinit(aTHX);
-    }
+    iter = SvOOK(hv) ? HvAUX(hv) : S_hv_auxinit(aTHX_ hv);
     return &(iter->xhv_riter);
 }
 
@@ -1754,10 +1802,7 @@ Perl_hv_eiter_p(pTHX_ HV *hv) {
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
 
-    iter = ((XPVHV *)SvANY(hv))->xhv_aux;
-    if (!iter) {
-	((XPVHV *)SvANY(hv))->xhv_aux = iter = S_hv_auxinit(aTHX);
-    }
+    iter = SvOOK(hv) ? HvAUX(hv) : S_hv_auxinit(aTHX_ hv);
     return &(iter->xhv_eiter);
 }
 
@@ -1768,13 +1813,13 @@ Perl_hv_riter_set(pTHX_ HV *hv, I32 riter) {
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
 
-
-    iter = ((XPVHV *)SvANY(hv))->xhv_aux;
-    if (!iter) {
+    if (SvOOK(hv)) {
+	iter = HvAUX(hv);
+    } else {
 	if (riter == -1)
 	    return;
 
-	((XPVHV *)SvANY(hv))->xhv_aux = iter = S_hv_auxinit(aTHX);
+	iter = S_hv_auxinit(aTHX_ hv);
     }
     iter->xhv_riter = riter;
 }
@@ -1786,14 +1831,15 @@ Perl_hv_eiter_set(pTHX_ HV *hv, HE *eiter) {
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
 
-    iter = ((XPVHV *)SvANY(hv))->xhv_aux;
-    if (!iter) {
+    if (SvOOK(hv)) {
+	iter = HvAUX(hv);
+    } else {
 	/* 0 is the default so don't go malloc()ing a new structure just to
 	   hold 0.  */
 	if (!eiter)
 	    return;
 
-	((XPVHV *)SvANY(hv))->xhv_aux = iter = S_hv_auxinit(aTHX);
+	iter = S_hv_auxinit(aTHX_ hv);
     }
     iter->xhv_eiter = eiter;
 }
@@ -1801,10 +1847,11 @@ Perl_hv_eiter_set(pTHX_ HV *hv, HE *eiter) {
 void
 Perl_hv_name_set(pTHX_ HV *hv, const char *name, I32 len, int flags)
 {
-    struct xpvhv_aux *iter = ((XPVHV *)SvANY(hv))->xhv_aux;
+    struct xpvhv_aux *iter;
     U32 hash;
 
-    if (iter) {
+    if (SvOOK(hv)) {
+	iter = HvAUX(hv);
 	if (iter->xhv_name) {
 	    unshare_hek_or_pvn(iter->xhv_name, 0, 0, 0);
 	}
@@ -1812,7 +1859,7 @@ Perl_hv_name_set(pTHX_ HV *hv, const char *name, I32 len, int flags)
 	if (name == 0)
 	    return;
 
-	((XPVHV *)SvANY(hv))->xhv_aux = iter = S_hv_auxinit(aTHX);
+	iter = S_hv_auxinit(aTHX_ hv);
     }
     PERL_HASH(hash, name, len);
     iter->xhv_name = name ? share_hek(name, len, hash) : 0;
@@ -1868,15 +1915,14 @@ Perl_hv_iternext_flags(pTHX_ HV *hv, I32 flags)
     if (!hv)
 	Perl_croak(aTHX_ "Bad hash");
     xhv = (XPVHV*)SvANY(hv);
-    iter = xhv->xhv_aux;
 
-    if (!iter) {
+    if (!SvOOK(hv)) {
 	/* Too many things (well, pp_each at least) merrily assume that you can
 	   call iv_iternext without calling hv_iterinit, so we'll have to deal
 	   with it.  */
 	hv_iterinit(hv);
-	iter = ((XPVHV *)SvANY(hv))->xhv_aux;
     }
+    iter = HvAUX(hv);
 
     oldentry = entry = iter->xhv_eiter; /* HvEITER(hv) */
 
@@ -1916,13 +1962,9 @@ Perl_hv_iternext_flags(pTHX_ HV *hv, I32 flags)
 	prime_env_iter();
 #endif
 
-    if (!HvARRAY(hv)) {
-	char *darray;
-	Newz(506, darray,
-	     PERL_HV_ARRAY_ALLOC_BYTES(xhv->xhv_max+1 /* HvMAX(hv)+1 */),
-	     char);
-	HvARRAY(hv) = (HE**) darray;
-    }
+    /* hv_iterint now ensures this.  */
+    assert (HvARRAY(hv));
+
     /* At start of hash, entry is NULL.  */
     if (entry)
     {
diff --git a/hv.h b/hv.h
index 2088c53310..a8f9b80ce0 100644
--- a/hv.h
+++ b/hv.h
@@ -39,6 +39,8 @@ struct xpvhv_aux {
     I32		xhv_riter;	/* current root of iterator */
 };
 
+#define HV_AUX_SIZE STRUCT_OFFSET(struct xpvhv_aux, xhv_array)
+
 /* hash structure: */
 /* This structure must match the beginning of struct xpvmg in sv.h. */
 struct xpvhv {
@@ -52,7 +54,6 @@ struct xpvhv {
     }		xiv_u;
     MAGIC*	xmg_magic;	/* magic for scalar array */
     HV*		xmg_stash;	/* class package */
-    struct xpvhv_aux *xhv_aux;
 };
 
 #define xhv_keys xiv_u.xivu_iv
@@ -70,7 +71,6 @@ typedef struct {
     }		xiv_u;
     MAGIC*	xmg_magic;	/* magic for scalar array */
     HV*		xmg_stash;	/* class package */
-    struct xpvhv_aux *xhv_aux;
 } xpvhv_allocated;
 #endif
 
@@ -206,23 +206,24 @@ C<SV*>.
 #define HvARRAY(hv)	(*(HE***)&((hv)->sv_u.svu_array))
 #define HvFILL(hv)	((XPVHV*)  SvANY(hv))->xhv_fill
 #define HvMAX(hv)	((XPVHV*)  SvANY(hv))->xhv_max
+/* This quite intentionally does no flag checking first. That's your
+   responsibility.  */
+#define HvAUX(hv)	((struct xpvhv_aux*)&(HvARRAY(hv)[HvMAX(hv)+1]))
 #define HvRITER(hv)	(*Perl_hv_riter_p(aTHX_ (HV*)(hv)))
 #define HvEITER(hv)	(*Perl_hv_eiter_p(aTHX_ (HV*)(hv)))
 #define HvRITER_set(hv,r)	Perl_hv_riter_set(aTHX_ (HV*)(hv), r)
 #define HvEITER_set(hv,e)	Perl_hv_eiter_set(aTHX_ (HV*)(hv), e)
-#define HvRITER_get(hv)	(((XPVHV *)SvANY(hv))->xhv_aux ? \
-			 ((struct xpvhv_aux*)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_riter : -1)
-#define HvEITER_get(hv)	(((XPVHV *)SvANY(hv))->xhv_aux ? \
-			 ((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_eiter : 0)
+#define HvRITER_get(hv)	(SvOOK(hv) ? HvAUX(hv)->xhv_riter : -1)
+#define HvEITER_get(hv)	(SvOOK(hv) ? HvAUX(hv)->xhv_eiter : 0)
 #define HvNAME(hv)	HvNAME_get(hv)
 /* FIXME - all of these should use a UTF8 aware API, which should also involve
    getting the length. */
 /* This macro may go away without notice.  */
-#define HvNAME_HEK(hv) (((XPVHV *)SvANY(hv))->xhv_aux && (((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_name) ? ((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_name: 0)
-#define HvNAME_get(hv)	(((XPVHV *)SvANY(hv))->xhv_aux ? \
-			 (((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_name) ? HEK_KEY(((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_name) : 0 : 0)
-#define HvNAMELEN_get(hv)	(((XPVHV *)SvANY(hv))->xhv_aux ? \
-			 (((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_name) ? HEK_LEN(((struct xpvhv_aux *)((XPVHV *)SvANY(hv))->xhv_aux)->xhv_name) : 0 : 0)
+#define HvNAME_HEK(hv) (SvOOK(hv) ? HvAUX(hv)->xhv_name : 0)
+#define HvNAME_get(hv)	((SvOOK(hv) && (HvAUX(hv)->xhv_name)) \
+			 ? HEK_KEY(HvAUX(hv)->xhv_name) : 0)
+#define HvNAMELEN_get(hv)	((SvOOK(hv) && (HvAUX(hv)->xhv_name)) \
+				 ? HEK_LEN(HvAUX(hv)->xhv_name) : 0)
 
 /* the number of keys (including any placeholers) */
 #define XHvTOTALKEYS(xhv)	((xhv)->xhv_keys)
diff --git a/sv.c b/sv.c
index 9bd3ab149a..33584a3299 100644
--- a/sv.c
+++ b/sv.c
@@ -1867,7 +1867,6 @@ Perl_sv_upgrade(pTHX_ register SV *sv, U32 mt)
 	break;
     case SVt_PVHV:
 	SvANY(sv) = new_XPVHV();
-	((XPVHV*) SvANY(sv))->xhv_aux = 0;
 	HvFILL(sv)	= 0;
 	HvMAX(sv)	= 0;
 	HvTOTALKEYS(sv)	= 0;
@@ -1983,6 +1982,8 @@ int
 Perl_sv_backoff(pTHX_ register SV *sv)
 {
     assert(SvOOK(sv));
+    assert(SvTYPE(sv) != SVt_PVHV);
+    assert(SvTYPE(sv) != SVt_PVAV);
     if (SvIVX(sv)) {
 	char *s = SvPVX(sv);
 	SvLEN_set(sv, SvLEN(sv) + SvIVX(sv));
@@ -10921,30 +10922,8 @@ Perl_sv_dup(pTHX_ SV *sstr, CLONE_PARAMS* param)
 	SvMAGIC_set(dstr, mg_dup(SvMAGIC(sstr), param));
 	SvSTASH_set(dstr, hv_dup_inc(SvSTASH(sstr), param));
 	{
-	    struct xpvhv_aux *aux = ((XPVHV *)SvANY(sstr))->xhv_aux;
 	    HEK *hvname = 0;
 
-	    if (aux) {
-		I32 riter = aux->xhv_riter;
-
-		hvname = aux->xhv_name;
-		if (hvname || riter != -1) {
-		    struct xpvhv_aux *d_aux;
-
-		    New(0, d_aux, 1, struct xpvhv_aux);
-
-		    d_aux->xhv_riter = riter;
-		    d_aux->xhv_eiter = 0;
-		    d_aux->xhv_name = hvname ? hek_dup(hvname, param) : hvname;
-
-		    ((XPVHV *)SvANY(dstr))->xhv_aux = d_aux;
-		} else {
-		    ((XPVHV *)SvANY(dstr))->xhv_aux = 0;
-		}
-	    }
-	    else {
-		((XPVHV *)SvANY(dstr))->xhv_aux = 0;
-	    }
 	    if (HvARRAY((HV*)sstr)) {
 		STRLEN i = 0;
 		XPVHV *dxhv = (XPVHV*)SvANY(dstr);
@@ -10952,7 +10931,8 @@ Perl_sv_dup(pTHX_ SV *sstr, CLONE_PARAMS* param)
 		char *darray;
 		/* FIXME - surely this doesn't need to be zeroed?  */
 		Newz(0, darray,
-		     PERL_HV_ARRAY_ALLOC_BYTES(dxhv->xhv_max+1), char);
+		     PERL_HV_ARRAY_ALLOC_BYTES(dxhv->xhv_max+1)
+		     + (SvOOK(sstr) ? sizeof(struct xpvhv_aux) : 0), char);
 		HvARRAY(dstr) = (HE**)darray;
 		while (i <= sxhv->xhv_max) {
 		    HvARRAY(dstr)[i]
@@ -10960,12 +10940,24 @@ Perl_sv_dup(pTHX_ SV *sstr, CLONE_PARAMS* param)
 				 (bool)!!HvSHAREKEYS(sstr), param);
 		    ++i;
 		}
-		HvEITER_set(dstr, he_dup(HvEITER_get(sstr),
-					 (bool)!!HvSHAREKEYS(sstr), param));
+		if (SvOOK(sstr)) {
+		    struct xpvhv_aux *saux = HvAUX(sstr);
+		    struct xpvhv_aux *daux = HvAUX(dstr);
+		    /* This flag isn't copied.  */
+		    /* SvOOK_on(hv) attacks the IV flags.  */
+		    SvFLAGS(dstr) |= SVf_OOK;
+
+		    hvname = saux->xhv_name;
+		    daux->xhv_name = hvname ? hek_dup(hvname, param) : hvname;
+
+		    daux->xhv_riter = saux->xhv_riter;
+		    daux->xhv_eiter = saux->xhv_eiter
+			? he_dup(saux->xhv_eiter, (bool)!!HvSHAREKEYS(sstr),
+				 param) : 0;
+		}
 	    }
 	    else {
 		SvPV_set(dstr, Nullch);
-		HvEITER_set((HV*)dstr, (HE*)NULL);
 	    }
 	    /* Record stashes for possible cloning in Perl_clone(). */
 	    if(hvname)
diff --git a/sv.h b/sv.h
index a8dcc5bffb..15d90a9e06 100644
--- a/sv.h
+++ b/sv.h
@@ -225,7 +225,10 @@ perform the upgrade if necessary.  See C<svtype>.
 #define SVf_ROK		0x00080000	/* has a valid reference pointer */
 
 #define SVf_FAKE	0x00100000	/* glob or lexical is just a copy */
-#define SVf_OOK		0x00200000	/* has valid offset value */
+#define SVf_OOK		0x00200000	/* has valid offset value
+					   For a PVHV this means that a
+					   hv_aux struct is present after the
+					   main array  */
 #define SVf_BREAK	0x00400000	/* refcnt is artificially low - used
 					 * by SV's in final arena  cleanup */
 #define SVf_READONLY	0x00800000	/* may not be modified */
diff --git a/t/op/magic.t b/t/op/magic.t
index 4e735414c2..dccb5634d5 100755
--- a/t/op/magic.t
+++ b/t/op/magic.t
@@ -358,7 +358,7 @@ if ($Is_miniperl) {
 
 # Make sure Errno hasn't been prematurely autoloaded
 
-   ok !defined %Errno::;
+   ok !keys %Errno::;
 
 # Test auto-loading of Errno when %! is used