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[perl #96942] [PATCH] Propagate lvalue context only to children of list ops which are not in void context.

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From:
Gerard Goossen
Date:
August 14, 2011 03:45
Subject:
[perl #96942] [PATCH] Propagate lvalue context only to children of list ops which are not in void context.
Message ID:
rt-3.6.HEAD-31297-1313318720-1386.96942-75-0@perl.org
# New Ticket Created by  Gerard Goossen 
# Please include the string:  [perl #96942]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=96942 >



This is a bug report for perl from gerard@ggoossen.net,
generated with the help of perlbug 1.39 running under perl 5.15.1.

>From b6d8ec44ecd2370b1cbebf8e0ea399594475cd7d Mon Sep 17 00:00:00 2001
From: Gerard Goossen <gerard@ggoossen.net>
Date: Sat, 13 Aug 2011 18:38:13 +0200
Subject: [PATCH] Propagate lvalue context only to children of list ops which
 are not in void context.

Children list ops might be in void context because the list is in scalar
context. A test that discarded elements in a list are not assigned lvalue
context is added.
Children of a list op might also be in void context because they are
special entersub ops for attributes. This patch makes the
OPpENTERSUB_NOMOD flag redundant.
---
 op.c        |    7 ++++++-
 t/op/list.t |    9 ++++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/op.c b/op.c
index 3d16001..3f5313d 100644
--- a/op.c
+++ b/op.c
@@ -1718,6 +1718,8 @@ Perl_op_lvalue_flags(pTHX_ OP *o, I32 type, U32 flags)
 	return o;
     }
 
+    assert( (o->op_flags & OPf_WANT) != OPf_WANT_VOID );
+
     switch (o->op_type) {
     case OP_UNDEF:
 	localize = 0;
@@ -2016,7 +2018,10 @@ Perl_op_lvalue_flags(pTHX_ OP *o, I32 type, U32 flags)
     case OP_LIST:
 	localize = 0;
 	for (kid = cLISTOPo->op_first; kid; kid = kid->op_sibling)
-	    op_lvalue(kid, type);
+	    /* elements might be in void context because the list is
+	       in scalar context or because they are attribute sub calls */
+	    if ( (kid->op_flags & OPf_WANT) != OPf_WANT_VOID )
+		op_lvalue(kid, type);
 	break;
 
     case OP_RETURN:
diff --git a/t/op/list.t b/t/op/list.t
index c6a0a9a..87045fc 100644
--- a/t/op/list.t
+++ b/t/op/list.t
@@ -6,7 +6,7 @@ BEGIN {
 }
 
 require "test.pl";
-plan( tests => 63 );
+plan( tests => 64 );
 
 @foo = (1, 2, 3, 4);
 cmp_ok($foo[0], '==', 1, 'first elem');
@@ -175,3 +175,10 @@ cmp_ok(join('',(1,2),3,(4,5)),'eq','12345','list (..).(..)');
     my @b = qw();
     is($#b, -1);
 }
+
+{
+    # comma operator with lvalue only propagates the lvalue context to
+    # the last operand.
+    ("const", my $x) ||= 1;
+    is( $x, 1 );
+}
-- 
1.7.5.4

---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.15.1:

Configured by gerard at Sun Aug 14 12:21:38 CEST 2011.

Summary of my perl5 (revision 5 version 15 subversion 1) configuration:
  Commit id: 699e6d637d01cb2033f3acfaf1d8ad76daf1227b
  Platform:
    osname=linux, osvers=2.6.39-2-686-pae, archname=i686-linux
    uname='linux zeus 2.6.39-2-686-pae #1 smp tue jul 5 03:48:49 utc 2011 i686 gnulinux '
    config_args='-des -DDEBUGGING -Doptimize=-O3 -g3 -Dusedevel -Dprefix=/home/gerard/perl/inst/blead-codegen'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=undef, use64bitall=undef, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O3 -g3',
    cppflags='-DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.6.1', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /usr/lib/i386-linux-gnu /usr/lib64
    libs=-lnsl -ldb -ldl -lm -lcrypt -lutil -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.13'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O3 -g3 -L/usr/local/lib -fstack-protector'

Locally applied patches:
    

---
@INC for perl 5.15.1:
    lib
    /home/gerard/perl/inst/blead-codegen/lib/site_perl/5.15.1/i686-linux
    /home/gerard/perl/inst/blead-codegen/lib/site_perl/5.15.1
    /home/gerard/perl/inst/blead-codegen/lib/5.15.1/i686-linux
    /home/gerard/perl/inst/blead-codegen/lib/5.15.1
    /home/gerard/perl/inst/blead-codegen/lib/site_perl
    .

---
Environment for perl 5.15.1:
    HOME=/home/gerard
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/gerard/bin:/usr/local/bin:/usr/bin:/bin:/usr/games
    PERL_BADLANG (unset)
    SHELL=/bin/bash


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