Fix handling left-hand-side undef when assigning a list

perl-5.33.0-list-assign-in-list-context-honour-LHS-undef.patch

@@ -0,0 +1,71 @@
+From 282d9dfeb4cea3c2d0335ba78faa3a9db931f1ec Mon Sep 17 00:00:00 2001
+From: David Mitchell <davem@iabyn.com>
+Date: Tue, 11 Aug 2020 13:58:51 +0100
+Subject: [PATCH] list assign in list context: honour LHS undef
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+GH #16685
+
+In
+
+    @a = ($x, undef, undef) = (1))
+
+@a should have 3 elements. v5.25.6-79-gb09ed995ad broke this and was
+returning one element.
+
+The fix is simple: that previous commit made it so that elements were
+pushed back onto the stack only if they weren't immortal, so
+&PL_sv_undef was getting skipped. Make it so they always are.
+
+Signed-off-by: Petr Písař <ppisar@redhat.com>
+---
+ pp_hot.c       |  2 +-
+ t/op/aassign.t | 10 +++++++++-
+ 2 files changed, 10 insertions(+), 2 deletions(-)
+
+diff --git a/pp_hot.c b/pp_hot.c
+index e9f1ffe7a4..3564dd7e12 100644
+--- a/pp_hot.c
++++ b/pp_hot.c
+@@ -2743,8 +2743,8 @@ PP(pp_aassign)
+ 	    if (!SvIMMORTAL(lsv)) {
+                 sv_set_undef(lsv);
+                 SvSETMAGIC(lsv);
+-                *relem++ = lsv;
+             }
++            *relem++ = lsv;
+ 	    break;
+         } /* switch */
+     } /* while */
+diff --git a/t/op/aassign.t b/t/op/aassign.t
+index 9128f9fd98..aa1f2c722c 100644
+--- a/t/op/aassign.t
++++ b/t/op/aassign.t
+@@ -595,7 +595,7 @@ SKIP: {
+ }
+ 
+ {
+-    # GH #17816
++    # GH #16685
+     # don't use the "1-arg on LHS can't be common" optimisation
+     # when there are undef's there
+     my $x = 1;
+@@ -603,5 +603,13 @@ SKIP: {
+     is("@a", "2 1", "GH #17816");
+ }
+ 
++{
++    # GH #17816
++    # honour trailing undef's in list context
++    my $x = 1;
++    my @a = (($x, undef, undef) = (1));
++    is(scalar @a, 3, "GH #17816");
++}
++
+ 
+ done_testing();
+-- 
+2.25.4
+

perl.spec

@@ -221,6 +221,10 @@ Patch30:        perl-5.33.0-fix-C-i-obj-where-obj-is-a-lexical.patch
 # in upstream after 5.33.0
 Patch31:        perl-5.33.0-list-assign-in-list-context-was-over-optimising.patch
 
+# Fix handling left-hand-side undef when assigning a list, GH#16685,
+# in upstream after 5.33.0
+Patch32:        perl-5.33.0-list-assign-in-list-context-honour-LHS-undef.patch
+
 # Link XS modules to libperl.so with EU::CBuilder on Linux, bug #960048
 Patch200:       perl-5.16.3-Link-XS-modules-to-libperl.so-with-EU-CBuilder-on-Li.patch
 
@@ -4239,6 +4243,7 @@ you're not running VMS, this module does nothing.
 %patch29 -p1
 %patch30 -p1
 %patch31 -p1
+%patch32 -p1
 %patch200 -p1
 %patch201 -p1
 
@@ -4277,6 +4282,7 @@ perl -x patchlevel.h \
     'Fedora Patch29: Fix an IO::Handle spurious error reported for regular file handles (GH#18019)' \
     'Fedora Patch30: Fix inheritance resolution of lexial objects in a debugger (GH#17661)' \
     'Fedora Patch31: Fix a misoptimization when assignig a list in a list context (GH#17816)' \
+    'Fedora Patch32: Fix handling left-hand-side undef when assigning a list (GH#16685)' \
     'Fedora Patch200: Link XS modules to libperl.so with EU::CBuilder on Linux' \
     'Fedora Patch201: Link XS modules to libperl.so with EU::MM on Linux' \
     %{nil}
@@ -6993,6 +6999,7 @@ popd
 * Thu Aug 27 2020 Petr Pisar <ppisar@redhat.com> - 4:5.32.0-462
 - Fix inheritance resolution of lexial objects in a debugger (GH#17661)
 - Fix a misoptimization when assignig a list in a list context (GH#17816)
+- Fix handling left-hand-side undef when assigning a list (GH#16685)
 
 * Fri Aug 21 2020 Jeff Law <law@redhat.com> - 4:5.32.0-461
 - Re-enable LTO