Re: [PATCH] Re: Storing &PL_sv_undef as a hash key with perl-5.8.x

From: "Marcus Holland-Moritz" <mhx-perl@gmx.net>
Message-ID: <006801c34efe$8aac1920$0c2f1fac@R2D2>

p4raw-id: //depot/perl@20224

diff --git a/dump.c b/dump.c
index d6b6558..52a43a9 100644 (file)
--- a/dump.c
+++ b/dump.c
@@ -160,7 +160,7 @@ Perl_sv_peek(pTHX_ SV *sv)
        sv_catpv(t, "WILD");
        goto finish;
     }
-    else if (sv == &PL_sv_undef || sv == &PL_sv_no || sv == &PL_sv_yes) {
+    else if (sv == &PL_sv_undef || sv == &PL_sv_no || sv == &PL_sv_yes || sv == &PL_sv_placeholder) {
        if (sv == &PL_sv_undef) {
            sv_catpv(t, "SV_UNDEF");
            if (!(SvFLAGS(sv) & (SVf_OK|SVf_OOK|SVs_OBJECT|
@@ -178,7 +178,7 @@ Perl_sv_peek(pTHX_ SV *sv)
                SvNVX(sv) == 0.0)
                goto finish;
        }
-       else {
+       else if (sv == &PL_sv_yes) {
            sv_catpv(t, "SV_YES");
            if (!(SvFLAGS(sv) & (SVf_ROK|SVf_OOK|SVs_OBJECT|
                                 SVs_GMG|SVs_SMG|SVs_RMG)) &&
@@ -189,6 +189,13 @@ Perl_sv_peek(pTHX_ SV *sv)
                SvNVX(sv) == 1.0)
                goto finish;
        }
+       else {
+           sv_catpv(t, "SV_PLACEHOLDER");
+           if (!(SvFLAGS(sv) & (SVf_OK|SVf_OOK|SVs_OBJECT|
+                                SVs_GMG|SVs_SMG|SVs_RMG)) &&
+               SvREADONLY(sv))
+               goto finish;
+       }
        sv_catpv(t, ":");
     }
     else if (SvREFCNT(sv) == 0) {

diff --git a/embedvar.h b/embedvar.h
index 98d8b21..2fe4840 100644 (file)
--- a/embedvar.h
+++ b/embedvar.h
@@ -396,6 +396,7 @@
 #define PL_sv_count            (vTHX->Isv_count)
 #define PL_sv_no               (vTHX->Isv_no)
 #define PL_sv_objcount         (vTHX->Isv_objcount)
+#define PL_sv_placeholder      (vTHX->Isv_placeholder)
 #define PL_sv_root             (vTHX->Isv_root)
 #define PL_sv_undef            (vTHX->Isv_undef)
 #define PL_sv_yes              (vTHX->Isv_yes)
@@ -700,6 +701,7 @@
 #define PL_Isv_count           PL_sv_count
 #define PL_Isv_no              PL_sv_no
 #define PL_Isv_objcount                PL_sv_objcount
+#define PL_Isv_placeholder     PL_sv_placeholder
 #define PL_Isv_root            PL_sv_root
 #define PL_Isv_undef           PL_sv_undef
 #define PL_Isv_yes             PL_sv_yes

diff --git a/ext/Storable/Storable.xs b/ext/Storable/Storable.xs
index 19470cb..055aefc 100644 (file)
--- a/ext/Storable/Storable.xs
+++ b/ext/Storable/Storable.xs
@@ -1237,13 +1237,13 @@ static void clean_store_context(stcxt_t *cxt)
        if (cxt->hseen) {
                hv_iterinit(cxt->hseen);
                while ((he = hv_iternext(cxt->hseen)))  /* Extra () for -Wall, grr.. */
-                       HeVAL(he) = &PL_sv_undef;
+                       HeVAL(he) = &PL_sv_placeholder;
        }
 
        if (cxt->hclass) {
                hv_iterinit(cxt->hclass);
                while ((he = hv_iternext(cxt->hclass))) /* Extra () for -Wall, grr.. */
-                       HeVAL(he) = &PL_sv_undef;
+                       HeVAL(he) = &PL_sv_placeholder;
        }
 
        /*
@@ -2208,7 +2208,11 @@ static int store_hash(stcxt_t *cxt, HV *hv)
                             = (((hash_flags & SHV_RESTRICTED)
                                 && SvREADONLY(val))
                                ? SHV_K_LOCKED : 0);
+#ifdef PL_sv_placeholder
+                        if (val == &PL_sv_placeholder)
+#else
                         if (val == &PL_sv_undef)
+#endif
                             flags |= SHV_K_PLACEHOLDER;
 
                        keyval = SvPV(key, keylen_tmp);
@@ -2304,7 +2308,11 @@ static int store_hash(stcxt_t *cxt, HV *hv)
                             = (((hash_flags & SHV_RESTRICTED)
                                 && SvREADONLY(val))
                                              ? SHV_K_LOCKED : 0);
+#ifdef PL_sv_placeholder
+                        if (val == &PL_sv_placeholder)
+#else
                         if (val == &PL_sv_undef)
+#endif
                             flags |= SHV_K_PLACEHOLDER;
 
                         hek = HeKEY_hek(he);
@@ -4896,7 +4904,7 @@ static SV *retrieve_flag_hash(stcxt_t *cxt, char *cname)
 
             if (flags & SHV_K_PLACEHOLDER) {
                 SvREFCNT_dec (sv);
-                sv = &PL_sv_undef;
+                sv = &PL_sv_placeholder;
                store_flags |= HVhek_PLACEHOLD;
            }
             if (flags & SHV_K_UTF8) {

diff --git a/hv.c b/hv.c
index 0bbebc6..78082d0 100644 (file)
--- a/hv.c
+++ b/hv.c
@@ -312,7 +312,7 @@ S_hv_fetch_flags(pTHX_ HV *hv, const char *key, I32 klen, I32 lval, int flags)
         if (flags & HVhek_FREEKEY)
             Safefree(key);
        /* if we find a placeholder, we pretend we haven't found anything */
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
            break;
        return &HeVAL(entry);
 
@@ -482,7 +482,7 @@ Perl_hv_fetch_ent(pTHX_ HV *hv, SV *keysv, I32 lval, register U32 hash)
        if (key != keysave)
            Safefree(key);
        /* if we find a placeholder, we pretend we haven't found anything */
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
            break;
        return entry;
     }
@@ -645,7 +645,7 @@ Perl_hv_store_flags(pTHX_ HV *hv, const char *key, I32 klen, SV *val,
            continue;
        if ((HeKFLAGS(entry) ^ flags) & HVhek_UTF8)
            continue;
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
            xhv->xhv_placeholders--; /* yes, can store into placeholder slot */
        else
            SvREFCNT_dec(HeVAL(entry));
@@ -653,7 +653,7 @@ Perl_hv_store_flags(pTHX_ HV *hv, const char *key, I32 klen, SV *val,
             /* We have been requested to insert a placeholder. Currently
                only Storable is allowed to do this.  */
             xhv->xhv_placeholders++;
-            HeVAL(entry) = &PL_sv_undef;
+            HeVAL(entry) = &PL_sv_placeholder;
         } else
             HeVAL(entry) = val;
 
@@ -696,7 +696,7 @@ Perl_hv_store_flags(pTHX_ HV *hv, const char *key, I32 klen, SV *val,
         /* We have been requested to insert a placeholder. Currently
            only Storable is allowed to do this.  */
         xhv->xhv_placeholders++;
-        HeVAL(entry) = &PL_sv_undef;
+        HeVAL(entry) = &PL_sv_placeholder;
     } else
         HeVAL(entry) = val;
     HeNEXT(entry) = *oentry;
@@ -820,7 +820,7 @@ Perl_hv_store_ent(pTHX_ HV *hv, SV *keysv, SV *val, U32 hash)
            continue;
        if ((HeKFLAGS(entry) ^ flags) & HVhek_UTF8)
            continue;
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
            xhv->xhv_placeholders--; /* yes, can store into placeholder slot */
        else
            SvREFCNT_dec(HeVAL(entry));
@@ -964,7 +964,7 @@ Perl_hv_delete(pTHX_ HV *hv, const char *key, I32 klen, I32 flags)
        if (k_flags & HVhek_FREEKEY)
            Safefree(key);
        /* if placeholder is here, it's already been deleted.... */
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
        {
            if (SvREADONLY(hv))
                return Nullsv;  /* if still SvREADONLY, leave it deleted. */
@@ -994,7 +994,7 @@ Perl_hv_delete(pTHX_ HV *hv, const char *key, I32 klen, I32 flags)
            sv = Nullsv;
        else {
            sv = sv_2mortal(HeVAL(entry));
-           HeVAL(entry) = &PL_sv_undef;
+           HeVAL(entry) = &PL_sv_placeholder;
        }
 
        /*
@@ -1004,7 +1004,7 @@ Perl_hv_delete(pTHX_ HV *hv, const char *key, I32 klen, I32 flags)
         * an error.
         */
        if (SvREADONLY(hv)) {
-           HeVAL(entry) = &PL_sv_undef;
+           HeVAL(entry) = &PL_sv_placeholder;
            /* We'll be saving this slot, so the number of allocated keys
             * doesn't go down, but the number placeholders goes up */
            xhv->xhv_placeholders++; /* HvPLACEHOLDERS(hv)++ */
@@ -1123,7 +1123,7 @@ Perl_hv_delete_ent(pTHX_ HV *hv, SV *keysv, I32 flags, U32 hash)
             Safefree(key);
 
        /* if placeholder is here, it's already been deleted.... */
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
        {
            if (SvREADONLY(hv))
                return Nullsv; /* if still SvREADONLY, leave it deleted. */
@@ -1152,7 +1152,7 @@ Perl_hv_delete_ent(pTHX_ HV *hv, SV *keysv, I32 flags, U32 hash)
            sv = Nullsv;
        else {
            sv = sv_2mortal(HeVAL(entry));
-           HeVAL(entry) = &PL_sv_undef;
+           HeVAL(entry) = &PL_sv_placeholder;
        }
 
        /*
@@ -1162,7 +1162,7 @@ Perl_hv_delete_ent(pTHX_ HV *hv, SV *keysv, I32 flags, U32 hash)
         * an error.
         */
        if (SvREADONLY(hv)) {
-           HeVAL(entry) = &PL_sv_undef;
+           HeVAL(entry) = &PL_sv_placeholder;
            /* We'll be saving this slot, so the number of allocated keys
             * doesn't go down, but the number placeholders goes up */
            xhv->xhv_placeholders++; /* HvPLACEHOLDERS(hv)++ */
@@ -1271,7 +1271,7 @@ Perl_hv_exists(pTHX_ HV *hv, const char *key, I32 klen)
        if (k_flags & HVhek_FREEKEY)
            Safefree(key);
        /* If we find the key, but the value is a placeholder, return false. */
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
            return FALSE;
 
        return TRUE;
@@ -1376,7 +1376,7 @@ Perl_hv_exists_ent(pTHX_ HV *hv, SV *keysv, U32 hash)
        if (k_flags & HVhek_FREEKEY)
            Safefree(key);
        /* If we find the key, but the value is a placeholder, return false. */
-       if (HeVAL(entry) == &PL_sv_undef)
+       if (HeVAL(entry) == &PL_sv_placeholder)
            return FALSE;
        return TRUE;
     }
@@ -1713,7 +1713,7 @@ Perl_hv_clear(pTHX_ HV *hv)
            entry = ((HE**)xhv->xhv_array)[i];
            for (; entry; entry = HeNEXT(entry)) {
                /* not already placeholder */
-               if (HeVAL(entry) != &PL_sv_undef) {
+               if (HeVAL(entry) != &PL_sv_placeholder) {
                    if (HeVAL(entry) && SvREADONLY(HeVAL(entry))) {
                        SV* keysv = hv_iterkeysv(entry);
                        Perl_croak(aTHX_
@@ -1721,7 +1721,7 @@ Perl_hv_clear(pTHX_ HV *hv)
                                   keysv);
                    }
                    SvREFCNT_dec(HeVAL(entry));
-                   HeVAL(entry) = &PL_sv_undef;
+                   HeVAL(entry) = &PL_sv_placeholder;
                    xhv->xhv_placeholders++; /* HvPLACEHOLDERS(hv)++ */
                }
            }
@@ -1875,9 +1875,8 @@ Returns entries from a hash iterator.  See C<hv_iterinit> and C<hv_iternext>.
 The C<flags> value will normally be zero; if HV_ITERNEXT_WANTPLACEHOLDERS is
 set the placeholders keys (for restricted hashes) will be returned in addition
 to normal keys. By default placeholders are automatically skipped over.
-Currently a placeholder is implemented with a value that is literally
-<&Perl_sv_undef> (a regular C<undef> value is a normal read-write SV for which
-C<!SvOK> is false). Note that the implementation of placeholders and
+Currently a placeholder is implemented with a value that is
+C<&Perl_sv_placeholder>. Note that the implementation of placeholders and
 restricted hashes may change, and the implementation currently is
 insufficiently abstracted for any change to be tidy.
 
@@ -1946,7 +1945,7 @@ Perl_hv_iternext_flags(pTHX_ HV *hv, I32 flags)
              * Skip past any placeholders -- don't want to include them in
              * any iteration.
              */
-            while (entry && HeVAL(entry) == &PL_sv_undef) {
+            while (entry && HeVAL(entry) == &PL_sv_placeholder) {
                 entry = HeNEXT(entry);
             }
        }
@@ -1966,7 +1965,7 @@ Perl_hv_iternext_flags(pTHX_ HV *hv, I32 flags)
         if (!(flags & HV_ITERNEXT_WANTPLACEHOLDERS)) {
             /* If we have an entry, but it's a placeholder, don't count it.
               Try the next.  */
-           while (entry && HeVAL(entry) == &PL_sv_undef)
+           while (entry && HeVAL(entry) == &PL_sv_placeholder)
                entry = HeNEXT(entry);
        }
        /* Will loop again if this linked list starts NULL

diff --git a/intrpvar.h b/intrpvar.h
index 6a34ea4..dbb9a12 100644 (file)
--- a/intrpvar.h
+++ b/intrpvar.h
@@ -531,6 +531,9 @@ PERLVAR(IDBassertion,   SV *)
 
 PERLVARI(Icv_has_eval, I32, 0) /* PL_compcv includes an entereval or similar */
 
+/* Restricted hashes placeholder value */
+PERLVAR(Isv_placeholder, SV)
+
 /* New variables must be added to the very end, before this comment,
  * for binary compatibility (the offsets of the old members must not change).
  * (Don't forget to add your variable also to perl_clone()!)

diff --git a/perl.c b/perl.c
index 0968e26..eb86c72 100644 (file)
--- a/perl.c
+++ b/perl.c
@@ -181,6 +181,9 @@ perl_construct(pTHXx)
            SvNV(&PL_sv_yes);
            SvREADONLY_on(&PL_sv_yes);
            SvREFCNT(&PL_sv_yes) = (~(U32)0)/2;
+
+           SvREADONLY_on(&PL_sv_placeholder);
+           SvREFCNT(&PL_sv_placeholder) = (~(U32)0)/2;
        }
 
        PL_sighandlerp = Perl_sighandler;
@@ -783,6 +786,9 @@ perl_destruct(pTHXx)
     SvREFCNT(&PL_sv_undef) = 0;
     SvREADONLY_off(&PL_sv_undef);
 
+    SvREFCNT(&PL_sv_placeholder) = 0;
+    SvREADONLY_off(&PL_sv_placeholder);
+
     Safefree(PL_origfilename);
     Safefree(PL_reg_start_tmp);
     if (PL_reg_curpm)

diff --git a/perlapi.h b/perlapi.h
index 524e84b..9af1ede 100644 (file)
--- a/perlapi.h
+++ b/perlapi.h
@@ -550,6 +550,8 @@ END_EXTERN_C
 #define PL_sv_no               (*Perl_Isv_no_ptr(aTHX))
 #undef  PL_sv_objcount
 #define PL_sv_objcount         (*Perl_Isv_objcount_ptr(aTHX))
+#undef  PL_sv_placeholder
+#define PL_sv_placeholder      (*Perl_Isv_placeholder_ptr(aTHX))
 #undef  PL_sv_root
 #define PL_sv_root             (*Perl_Isv_root_ptr(aTHX))
 #undef  PL_sv_undef

diff --git a/sv.c b/sv.c
index c31ada7..45d09d0 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -10913,6 +10913,11 @@ perl_clone_using(PerlInterpreter *proto_perl, UV flags,
     SvNVX(&PL_sv_yes)          = 1;
     ptr_table_store(PL_ptr_table, &proto_perl->Isv_yes, &PL_sv_yes);
 
+    SvANY(&PL_sv_placeholder)  = NULL;
+    SvREFCNT(&PL_sv_placeholder)= (~(U32)0)/2;
+    SvFLAGS(&PL_sv_placeholder)        = SVf_READONLY|SVt_NULL;
+    ptr_table_store(PL_ptr_table, &proto_perl->Isv_placeholder, &PL_sv_placeholder);
+
     /* create (a non-shared!) shared string table */
     PL_strtab          = newHV();
     HvSHAREKEYS_off(PL_strtab);

diff --git a/universal.c b/universal.c
index 9ee3e21..6ba5a13 100644 (file)
--- a/universal.c
+++ b/universal.c
@@ -755,7 +755,7 @@ XS(XS_Internals_hv_clear_placehold)
             && items) {
             SV *val = hv_iterval(hv, entry);
 
-            if (val == &PL_sv_undef) {
+            if (val == &PL_sv_placeholder) {
 
                 /* It seems that I have to go back in the front of the hash
                    API to delete a hash, even though I have a HE structure