On scope end, delete localized array elements that should not exist anymore, so that...

diff --git a/pp.c b/pp.c
index bdbe010..aacb789 100644 (file)
--- a/pp.c
+++ b/pp.c
@@ -3912,7 +3912,17 @@ PP(pp_aslice)
 
     if (SvTYPE(av) == SVt_PVAV) {
        const I32 arybase = CopARYBASE_get(PL_curcop);
-       if (lval && PL_op->op_private & OPpLVAL_INTRO) {
+       const bool localizing = PL_op->op_private & OPpLVAL_INTRO;
+       bool can_preserve = FALSE;
+
+       if (localizing) {
+           MAGIC *mg;
+           HV *stash;
+
+           can_preserve = SvCANEXISTDELETE(av);
+       }
+
+       if (lval && localizing) {
            register SV **svp;
            I32 max = -1;
            for (svp = MARK + 1; svp <= SP; svp++) {
@@ -3923,18 +3933,32 @@ PP(pp_aslice)
            if (max > AvMAX(av))
                av_extend(av, max);
        }
+
        while (++MARK <= SP) {
            register SV **svp;
            I32 elem = SvIV(*MARK);
+           bool preeminent = TRUE;
 
            if (elem > 0)
                elem -= arybase;
+           if (localizing && can_preserve) {
+               /* If we can determine whether the element exist,
+                * Try to preserve the existenceness of a tied array
+                * element by using EXISTS and DELETE if possible.
+                * Fallback to FETCH and STORE otherwise. */
+               preeminent = av_exists(av, elem);
+           }
+
            svp = av_fetch(av, elem, lval);
            if (lval) {
                if (!svp || *svp == &PL_sv_undef)
                    DIE(aTHX_ PL_no_aelem, elem);
-               if (PL_op->op_private & OPpLVAL_INTRO)
-                   save_aelem(av, elem, svp);
+               if (localizing) {
+                   if (preeminent)
+                       save_aelem(av, elem, svp);
+                   else
+                       SAVEADELETE(av, elem);
+               }
            }
            *MARK = svp ? *svp : &PL_sv_undef;
        }

diff --git a/pp_hot.c b/pp_hot.c
index 88fe838..66c36cb 100644 (file)
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2913,6 +2913,8 @@ PP(pp_aelem)
     AV *const av = MUTABLE_AV(POPs);
     const U32 lval = PL_op->op_flags & OPf_MOD || LVRET;
     const U32 defer = (PL_op->op_private & OPpLVAL_DEFER) && (elem > av_len(av));
+    const bool localizing = PL_op->op_private & OPpLVAL_INTRO;
+    bool preeminent = TRUE;
     SV *sv;
 
     if (SvROK(elemsv) && !SvGAMAGIC(elemsv) && ckWARN(WARN_MISC))
@@ -2923,6 +2925,19 @@ PP(pp_aelem)
        elem -= CopARYBASE_get(PL_curcop);
     if (SvTYPE(av) != SVt_PVAV)
        RETPUSHUNDEF;
+
+    if (localizing) {
+       MAGIC *mg;
+       HV *stash;
+
+       /* If we can determine whether the element exist,
+        * Try to preserve the existenceness of a tied array
+        * element by using EXISTS and DELETE if possible.
+        * Fallback to FETCH and STORE otherwise. */
+       if (SvCANEXISTDELETE(av))
+           preeminent = av_exists(av, elem);
+    }
+
     svp = av_fetch(av, elem, lval && !defer);
     if (lval) {
 #ifdef PERL_MALLOC_WRAP
@@ -2952,8 +2967,12 @@ PP(pp_aelem)
            PUSHs(lv);
            RETURN;
        }
-       if (PL_op->op_private & OPpLVAL_INTRO)
-           save_aelem(av, elem, svp);
+       if (localizing) {
+           if (preeminent)
+               save_aelem(av, elem, svp);
+           else
+               SAVEADELETE(av, elem);
+       }
        else if (PL_op->op_private & OPpDEREF)
            vivify_ref(*svp, PL_op->op_private & OPpDEREF);
     }

diff --git a/t/op/local.t b/t/op/local.t
index 5bf56af..24acbff 100755 (executable)
--- a/t/op/local.t
+++ b/t/op/local.t
@@ -5,7 +5,7 @@ BEGIN {
     @INC = qw(. ../lib);
     require './test.pl';
 }
-plan tests => 123;
+plan tests => 183;
 
 my $list_assignment_supported = 1;
 
@@ -96,6 +96,58 @@ ok(!defined $a[0]);
 
 @a = ('a', 'b', 'c');
 {
+    local($a[4]) = 'x';
+    ok(!defined $a[3]);
+    is($a[4], 'x');
+}
+is(scalar(@a), 3);
+ok(!exists $a[3]);
+ok(!exists $a[4]);
+
+@a = ('a', 'b', 'c');
+{
+    local($a[5]) = 'z';
+    $a[4] = 'y';
+    ok(!defined $a[3]);
+    is($a[4], 'y');
+    is($a[5], 'z');
+}
+is(scalar(@a), 5);
+ok(!defined $a[3]);
+is($a[4], 'y');
+ok(!exists $a[5]);
+
+@a = ('a', 'b', 'c');
+{
+    local(@a[4,6]) = ('x', 'z');
+    ok(!defined $a[3]);
+    is($a[4], 'x');
+    ok(!defined $a[5]);
+    is($a[6], 'z');
+}
+is(scalar(@a), 3);
+ok(!exists $a[3]);
+ok(!exists $a[4]);
+ok(!exists $a[5]);
+ok(!exists $a[6]);
+
+@a = ('a', 'b', 'c');
+{
+    local(@a[4,6]) = ('x', 'z');
+    $a[5] = 'y';
+    ok(!defined $a[3]);
+    is($a[4], 'x');
+    is($a[5], 'y');
+    is($a[6], 'z');
+}
+is(scalar(@a), 6);
+ok(!defined $a[3]);
+ok(!defined $a[4]);
+is($a[5], 'y');
+ok(!exists $a[6]);
+
+@a = ('a', 'b', 'c');
+{
     local($a[1]) = "X";
     shift @a;
 }
@@ -145,6 +197,8 @@ is($m, 5);
     sub TIEARRAY { bless [], $_[0] }
     sub STORE { print "# STORE [@_]\n"; $_[0]->[$_[1]] = $_[2] }
     sub FETCH { my $v = $_[0]->[$_[1]]; print "# FETCH [@_=$v]\n"; $v }
+    sub EXISTS { print "# EXISTS [@_]\n"; exists $_[0]->[$_[1]]; }
+    sub DELETE { print "# DELETE [@_]\n"; delete $_[0]->[$_[1]]; }
     sub CLEAR { print "# CLEAR [@_]\n"; @{$_[0]} = (); }
     sub FETCHSIZE { scalar(@{$_[0]}) }
     sub SHIFT { shift (@{$_[0]}) }
@@ -169,6 +223,60 @@ ok(!defined $a[0]);
     is("@a", $d);
 }
 
+# local() should preserve the existenceness of tied array elements
+@a = ('a', 'b', 'c');
+{
+    local($a[4]) = 'x';
+    ok(!defined $a[3]);
+    is($a[4], 'x');
+}
+is(scalar(@a), 3);
+ok(!exists $a[3]);
+ok(!exists $a[4]);
+
+@a = ('a', 'b', 'c');
+{
+    local($a[5]) = 'z';
+    $a[4] = 'y';
+    ok(!defined $a[3]);
+    is($a[4], 'y');
+    is($a[5], 'z');
+}
+is(scalar(@a), 5);
+ok(!defined $a[3]);
+is($a[4], 'y');
+ok(!exists $a[5]);
+
+@a = ('a', 'b', 'c');
+{
+    local(@a[4,6]) = ('x', 'z');
+    ok(!defined $a[3]);
+    is($a[4], 'x');
+    ok(!defined $a[5]);
+    is($a[6], 'z');
+}
+is(scalar(@a), 3);
+ok(!exists $a[3]);
+ok(!exists $a[4]);
+ok(!exists $a[5]);
+ok(!exists $a[6]);
+
+@a = ('a', 'b', 'c');
+{
+    local(@a[4,6]) = ('x', 'z');
+    $a[5] = 'y';
+    ok(!defined $a[3]);
+    is($a[4], 'x');
+    is($a[5], 'y');
+    is($a[6], 'z');
+}
+is(scalar(@a), 6);
+ok(!defined $a[3]);
+ok(!defined $a[4]);
+is($a[5], 'y');
+ok(!exists $a[6]);
+
+# see if localization works on tied hashes
 {
     package TH;
     sub TIEHASH { bless {}, $_[0] }
@@ -181,7 +289,6 @@ ok(!defined $a[0]);
     sub NEXTKEY { print "# NEXTKEY [@_]\n"; each %{$_[0]} }
 }
 
-# see if localization works on tied hashes
 tie %h, 'TH';
 %h = ('a' => 1, 'b' => 2, 'c' => 3);