Fix sorting tied arrays
This commit is contained in:
Petr Písař
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5b4184a6e3
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From 3eb35b099f783db0ec40f0ca9f20fd1666c54cdb Mon Sep 17 00:00:00 2001
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From: Yves Orton <demerphq@gmail.com>
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Date: Thu, 30 Jan 2020 09:36:37 +0100
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Subject: [PATCH] perltie.pod: rework example code so EXTEND is a no-op
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Most tied array implementations can and should NO-OP the EXTEND
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method, and the sample code should not conflate EXTEND with STORESIZE.
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EXTEND is actually less usefully used by the core than it could be
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as AvMAX() does not have an equivalent tied method. So we cannot
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check if we need to extend for a tied array.
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This is related to [rt.cpan.org #39196] / Issue #17496.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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pod/perltie.pod | 18 +++++++++++++-----
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1 file changed, 13 insertions(+), 5 deletions(-)
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diff --git a/pod/perltie.pod b/pod/perltie.pod
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index 2d433e8204..1bb220691b 100644
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--- a/pod/perltie.pod
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+++ b/pod/perltie.pod
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@@ -301,7 +301,7 @@ spaces so we have a little more work to do here:
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croak "length of $value is greater than $self->{ELEMSIZE}";
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}
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# fill in the blanks
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- $self->EXTEND( $index ) if $index > $self->FETCHSIZE();
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+ $self->STORESIZE( $index ) if $index > $self->FETCHSIZE();
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# right justify to keep element size for smaller elements
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$self->{ARRAY}->[$index] = sprintf "%$self->{ELEMSIZE}s", $value;
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}
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@@ -351,16 +351,24 @@ X<EXTEND>
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Informative call that array is likely to grow to have I<count> entries.
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Can be used to optimize allocation. This method need do nothing.
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-In our example, we want to make sure there are no blank (C<undef>)
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-entries, so C<EXTEND> will make use of C<STORESIZE> to fill elements
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-as needed:
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+In our example there is no reason to implement this method, so we leave
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+it as a no-op. This method is only relevant to tied array implementations
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+where there is the possibility of having the allocated size of the array
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+be larger than is visible to a perl programmer inspecting the size of the
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+array. Many tied array implementations will have no reason to implement it.
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sub EXTEND {
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my $self = shift;
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my $count = shift;
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- $self->STORESIZE( $count );
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+ # nothing to see here, move along.
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}
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+B<NOTE:> It is generally an error to make this equivalent to STORESIZE.
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+Perl may from time to time call EXTEND without wanting to actually change
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+the array size directly. Any tied array should function correctly if this
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+method is a no-op, even if perhaps they might not be as efficient as they
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+would if this method was implemented.
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+
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=item EXISTS this, key
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X<EXISTS>
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--
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2.21.1
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@ -0,0 +1,142 @@
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From 2b301921ff7682e54ab74ad30dbf2ce1c9fc24b1 Mon Sep 17 00:00:00 2001
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From: Yves Orton <demerphq@gmail.com>
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Date: Fri, 31 Jan 2020 15:34:48 +0100
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Subject: [PATCH] pp_sort.c: fix fencepost error in call to av_extend()
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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In [rt.cpan.org #39196] issue #17496 there is a report
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that Tie::File produced spurious blank lines in the file
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after
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@tied= sort @tied;
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it turns out that this is because Tie::File treats
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EXTEND similarly to STORESIZE (which is arguably not
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entirely correct, but also not that weird) coupled
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with an off by one error in the calls to av_extend()
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in pp_sort.
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This patch fixes the fencepost error, adds some comments
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to av_extend() to make it clear what it is doing, and
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adds a test that EXTEND is called by this code with
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correct argument.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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av.c | 18 ++++++++++++++++--
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pp_sort.c | 5 +++--
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t/op/sort.t | 23 +++++++++++++++++++++--
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3 files changed, 40 insertions(+), 6 deletions(-)
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diff --git a/av.c b/av.c
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index 918844c376..27b2f12032 100644
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--- a/av.c
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+++ b/av.c
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@@ -55,8 +55,13 @@ Perl_av_reify(pTHX_ AV *av)
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/*
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=for apidoc av_extend
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-Pre-extend an array. The C<key> is the index to which the array should be
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-extended.
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+Pre-extend an array so that it is capable of storing values at indexes
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+C<0..key>. Thus C<av_extend(av,99)> guarantees that the array can store 100
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+elements, i.e. that C<av_store(av, 0, sv)> through C<av_store(av, 99, sv)>
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+on a plain array will work without any further memory allocation.
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+
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+If the av argument is a tied array then will call the C<EXTEND> tied
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+array method with an argument of C<(key+1)>.
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=cut
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*/
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@@ -72,6 +77,15 @@ Perl_av_extend(pTHX_ AV *av, SSize_t key)
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mg = SvTIED_mg((const SV *)av, PERL_MAGIC_tied);
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if (mg) {
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SV *arg1 = sv_newmortal();
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+ /* NOTE: the API for av_extend() is NOT the same as the tie method EXTEND.
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+ *
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+ * The C function takes an *index* (assumes 0 indexed arrays) and ensures
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+ * that the array is at least as large as the index provided.
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+ *
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+ * The tied array method EXTEND takes a *count* and ensures that the array
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+ * is at least that many elements large. Thus we have to +1 the key when
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+ * we call the tied method.
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+ */
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sv_setiv(arg1, (IV)(key + 1));
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Perl_magic_methcall(aTHX_ MUTABLE_SV(av), mg, SV_CONST(EXTEND), G_DISCARD, 1,
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arg1);
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diff --git a/pp_sort.c b/pp_sort.c
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index 0c5efb0869..4f81aaab7e 100644
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--- a/pp_sort.c
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+++ b/pp_sort.c
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@@ -1067,7 +1067,8 @@ PP(pp_sort)
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for (i = 0; i < max; i++)
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base[i] = newSVsv(base[i]);
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av_clear(av);
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- av_extend(av, max);
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+ if (max)
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+ av_extend(av, max-1);
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for (i=0; i < max; i++) {
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SV * const sv = base[i];
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SV ** const didstore = av_store(av, i, sv);
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@@ -1094,7 +1095,7 @@ PP(pp_sort)
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}
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av_clear(av);
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if (max > 0) {
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- av_extend(av, max);
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+ av_extend(av, max-1);
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Copy(base, AvARRAY(av), max, SV*);
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}
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AvFILLp(av) = max - 1;
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diff --git a/t/op/sort.t b/t/op/sort.t
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index d201f00afd..f2e139dff0 100644
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--- a/t/op/sort.t
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+++ b/t/op/sort.t
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@@ -7,7 +7,8 @@ BEGIN {
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set_up_inc('../lib');
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}
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use warnings;
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-plan(tests => 199);
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+plan(tests => 203);
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+use Tie::Array; # we need to test sorting tied arrays
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# these shouldn't hang
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{
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@@ -433,7 +434,6 @@ cmp_ok($x,'eq','123',q(optimized-away comparison block doesn't take any other ar
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@a = qw(b c a); $r1 = \$a[1]; @a = sort mysort @a; $r2 = \$a[0];
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is "$$r1-$$r2-@a", "c-c-c b a", "inplace sort with function of lexical";
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- use Tie::Array;
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my @t;
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tie @t, 'Tie::StdArray';
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@@ -494,6 +494,25 @@ cmp_ok($x,'eq','123',q(optimized-away comparison block doesn't take any other ar
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is ("@a", "3 4 5", "RT #128340");
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}
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+{
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+ @Tied_Array_EXTEND_Test::ISA= 'Tie::StdArray';
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+ my $extend_count;
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+ sub Tied_Array_EXTEND_Test::EXTEND {
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+ $extend_count= $_[1];
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+ return;
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+ }
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+ my @t;
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+ tie @t, "Tied_Array_EXTEND_Test";
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+ is($extend_count, undef, "test that EXTEND has not been called prior to initialization");
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+ $t[0]=3;
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+ $t[1]=1;
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+ $t[2]=2;
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+ is($extend_count, undef, "test that EXTEND has not been called during initialization");
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+ @t= sort @t;
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+ is($extend_count, 3, "test that EXTEND was called with an argument of 3 by pp_sort()");
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+ is("@t","1 2 3","test that sorting the tied array worked even though EXTEND is a no-op");
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+}
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+
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# Test optimisations of reversed sorts. As we now guarantee stability by
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# default, # optimisations which do not provide this are bogus.
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--
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2.21.1
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@ -318,6 +318,10 @@ Patch78: perl-5.31.8-perlio.c-make-unix-close-method-call-underlaying-lay
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# in upstream after 5.31.8
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Patch79: perl-5.31.8-only-install-ExtUtils-XSSymSet-man-page-on-VMS.patch
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# Fix sorting tied arrays, GH#17496, in upstream after 5.31.8
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Patch80: perl-5.31.8-perltie.pod-rework-example-code-so-EXTEND-is-a-no-op.patch
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Patch81: perl-5.31.8-pp_sort.c-fix-fencepost-error-in-call-to-av_extend.patch
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# Link XS modules to libperl.so with EU::CBuilder on Linux, bug #960048
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Patch200: perl-5.16.3-Link-XS-modules-to-libperl.so-with-EU-CBuilder-on-Li.patch
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@ -4383,6 +4387,8 @@ you're not running VMS, this module does nothing.
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%patch77 -p1
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%patch78 -p1
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%patch79 -p1
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%patch80 -p1
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%patch81 -p1
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%patch200 -p1
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%patch201 -p1
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@ -4455,6 +4461,8 @@ perl -x patchlevel.h \
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'Fedora Patch77: Fix thread-safety of IO::Handle (GH#14816)' \
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'Fedora Patch78: Close :unix PerlIO layers properly' \
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'Fedora Patch79: Only install ExtUtils::XSSymSet manual page on VMS (GH#17424)' \
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'Fedora Patch80: Fix sorting tied arrays (GH#17496)' \
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'Fedora Patch81: Fix sorting tied arrays (GH#17496)' \
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'Fedora Patch200: Link XS modules to libperl.so with EU::CBuilder on Linux' \
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'Fedora Patch201: Link XS modules to libperl.so with EU::MM on Linux' \
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%{nil}
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@ -7216,6 +7224,7 @@ popd
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- Prevent from an integer overflow in POSIX::SigSet()
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- Fix thread-safety of IO::Handle (GH#14816)
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- Close :unix PerlIO layers properly
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- Fix sorting tied arrays (GH#17496)
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* Mon Mar 16 2020 Jitka Plesnikova <jplesnik@redhat.com> - 4:5.30.2-452
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- 5.30.2 bump (see <https://metacpan.org/pod/release/SHAY/perl-5.30.2/pod/perldelta.pod>
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