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lvalue+signature example: should not return read-only value #16389

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p5pRT opened this issue Jan 28, 2018 · 4 comments
Closed

lvalue+signature example: should not return read-only value #16389

p5pRT opened this issue Jan 28, 2018 · 4 comments

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@p5pRT
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@p5pRT p5pRT commented Jan 28, 2018

Migrated from rt.perl.org#132776 (status was 'resolved')

Searchable as RT132776$

@p5pRT
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@p5pRT p5pRT commented Jan 28, 2018

From @eserte

This is a bug report for perl from slaven@​rezic.de,
generated with the help of perlbug 1.41 running under perl 5.27.8.


A minor nit in perl5.27.8's perldelta.pod​: the two examples

  sub f :lvalue ($a, $b) { 1 }; # 5.20; 5.28 onwards
  sub f ($a, $b) :lvalue { 1 }; # 5.22 - 5.26

don't work because a read-only value is returned. A complete test script​:

#!/usr/bin/perl
use strict;
use feature 'signatures';
no warnings 'experimental';
sub f :lvalue ($a, $b) { 1 };
f(1,2) = 123;
__END__

Output is​:

Can't return a readonly value from lvalue subroutine at signatures.pl line 5.

Probably using a variable here would be better.



Flags​:
  category=docs
  severity=low


Site configuration information for perl 5.27.8​:

Configured by eserte at Sat Jan 20 09​:22​:10 CET 2018.

Summary of my perl5 (revision 5 version 27 subversion 8) configuration​:
 
  Platform​:
  osname=linux
  osvers=3.16.0-4-amd64
  archname=x86_64-linux
  uname='linux cabulja 3.16.0-4-amd64 #1 smp debian 3.16.51-3 (2017-12-13) x86_64 gnulinux '
  config_args='-ds -e -Dprefix=/opt/perl-5.27.8 -Dusedevel -Dusemallocwrap=no -Dcf_email=srezic@​cpan.org'
  hint=recommended
  useposix=true
  d_sigaction=define
  useithreads=undef
  usemultiplicity=undef
  use64bitint=define
  use64bitall=define
  uselongdouble=undef
  usemymalloc=n
  default_inc_excludes_dot=define
  bincompat5005=undef
  Compiler​:
  cc='cc'
  ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
  optimize='-O2'
  cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
  ccversion=''
  gccversion='4.9.2'
  gccosandvers=''
  intsize=4
  longsize=8
  ptrsize=8
  doublesize=8
  byteorder=12345678
  doublekind=3
  d_longlong=define
  longlongsize=8
  d_longdbl=define
  longdblsize=16
  longdblkind=3
  ivtype='long'
  ivsize=8
  nvtype='double'
  nvsize=8
  Off_t='off_t'
  lseeksize=8
  alignbytes=8
  prototype=define
  Linker and Libraries​:
  ld='cc'
  ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
  libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
  perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.19.so
  so=so
  useshrplib=false
  libperl=libperl.a
  gnulibc_version='2.19'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs
  dlext=so
  d_dlsymun=undef
  ccdlflags='-Wl,-E'
  cccdlflags='-fPIC'
  lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'


@​INC for perl 5.27.8​:
  /opt/perl-5.27.8/lib/site_perl/5.27.8/x86_64-linux
  /opt/perl-5.27.8/lib/site_perl/5.27.8
  /opt/perl-5.27.8/lib/5.27.8/x86_64-linux
  /opt/perl-5.27.8/lib/5.27.8


Environment for perl 5.27.8​:
  HOME=/home/eserte
  LANG=en_US.UTF-8
  LANGUAGE (unset)
  LD_LIBRARY_PATH (unset)
  LOGDIR (unset)
  PATH=/usr/local/bin​:/usr/bin​:/bin​:/usr/local/sbin​:/usr/sbin​:/sbin​:/home/eserte/bin/linux-gnu​:/home/eserte/bin/sh​:/home/eserte/bin​:/home/eserte/bin/pistachio-perl/bin​:/usr/games​:/home/eserte/devel
  PERLDOC=-MPod​::Perldoc​::ToTextOverstrike
  PERL_BADLANG (unset)
  SHELL=/bin/zsh

@p5pRT
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@p5pRT p5pRT commented Feb 20, 2018

From @iabyn

On Sun, Jan 28, 2018 at 01​:39​:13AM -0800, slaven@​rezic.de wrote​:

A minor nit in perl5.27.8's perldelta.pod​: the two examples

sub f :lvalue \($a\, $b\) \{ 1 \}; \# 5\.20; 5\.28 onwards
sub f \($a\, $b\) :lvalue \{ 1 \}; \# 5\.22 \- 5\.26

don't work because a read-only value is returned. A complete test script​:

Fixed with v5.27.8-346-g2a71223

--
"There's something wrong with our bloody ships today, Chatfield."
  -- Admiral Beatty at the Battle of Jutland, 31st May 1916.

@p5pRT
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@p5pRT p5pRT commented Feb 20, 2018

The RT System itself - Status changed from 'new' to 'open'

@p5pRT
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@p5pRT p5pRT commented Feb 20, 2018

@iabyn - Status changed from 'open' to 'resolved'

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