[perl #37315] 'my' with 'if 0' retains old value

# New Ticket Created by  "herington, dean" 
# Please include the string:  [perl #37315]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/rt3/Ticket/Display.html?id=37315 >


This is a bug report for perl from herington_dean@emc.com
<mailto:herington_dean@emc.com> ,
generated with the help of perlbug 1.35 running under perl v5.8.4.
 

-----------------------------------------------------------------
Running the following program outputs:
  Perl 5.008004
  undef
  undef
  undef
  2
but it should output:
  Perl 5.008004
  undef
  undef
  undef
  undef
 

#!/usr/bin/perl -w
 
print "Perl $]\n";
 
sub show {
    my ($val) = @_;
    if (! defined $val) {
        print "undef\n";
    } else {
        print "$val\n";
    }
}
 
sub sb {
 
    my $v1;
    $v1 = -1 if 0;
 
    my $v2 = -2 if 0;
 
    show $v1;
    show $v2;
 
    $v1 = 1;
    $v2 = 2;
 
}
 
sb;
sb;
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=high
---
Site configuration information for perl v5.8.4:
 
Summary of my perl5 (revision 5 version 8 subversion 4) configuration:
  Platform:
    osname=solaris, osvers=2.10, archname=sun4-solaris-64int
    uname='sunos localhost 5.10 sun4u sparc SUNW,Ultra-2'
    config_args=''
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef
usemultiplicity=undef
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=define use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -xarch=v8
-D_TS_ERRNO',
    optimize='-xO3 -xspace -xildoff',
    cppflags=''
    ccversion='Sun WorkShop', gccversion='', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=87654321
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =''
    libpth=/lib /usr/lib /usr/ccs/lib
    libs=-lsocket -lnsl -ldl -lm -lc
    perllibs=-lsocket -lnsl -ldl -lm -lc
    libc=/lib/libc.so, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-R
/usr/perl5/5.8.4/lib/sun4-solaris-64int/CORE'
    cccdlflags='-KPIC', lddlflags='-G'
 
Locally applied patches:
    22667 The optree builder was looping when constructing the ops ...
    22715 Upgrade to FileCache 1.04
    22733 Missing copyright in the README.
    22746 fix a coredump caused by rv2gv not fully converting a PV ...
    22755 Fix 29149 - another UTF8 cache bug hit by substr.
    22774 [perl #28938] split could leave an array without ...
    22775 [perl #29127] scalar delete of empty slice returned garbage
    22776 [perl #28986] perl -e \"open m\" crashes Perl
    22777 add test for change #22776 (\"open m\" crashes Perl)
    22778 add test for change #22746 ([perl #29102] Crash on assign ...
    22781 [perl #29340] Bizarre copy of ARRAY make sure a pad op's ...
    22796 [perl #29346] Double warning for int(undef) and abs(undef) ...
    22818 BOM-marked and (BOMless) UTF-16 scripts not working
    22823 [perl #29581] glob() misses a lot of matches
    22827 Smoke [5.9.2] 22818 FAIL(F) MSWin32 WinXP/.Net SP1 (x86/1 cpu)
    22830 [perl #29637] Thread creation time is hypersensitive
    22831 improve hashing algorithm for ptr tables in perl_clone: ...
    22839 [perl #29790] Optimization busted: '@a <mailto:'@a>  = \"b\", sort
@a' ...
    22850 [PATCH] 'perl -v' fails if local_patches contains code snippets
    22852 TEST needs to ignore SCM files
    22886 Pod::Find should ignore SCM files and dirs
    22888 Remove redundant %SIG assignments from FileCache
    23006 [perl #30509] use encoding and \"eq\" cause memory leak
    23074 Segfault using HTML::Entities
    23106 Numeric comparison operators mustn't compare addresses of ...
    23320 [perl #30066] Memory leak in nested shared data structures ...
    23321 [perl #31459] Bug in read()
 
---
@INC for perl v5.8.4:
    /usr/perl5/5.8.4/lib/sun4-solaris-64int
    /usr/perl5/5.8.4/lib
    /usr/perl5/site_perl/5.8.4/sun4-solaris-64int
    /usr/perl5/site_perl/5.8.4
    /usr/perl5/site_perl
    /usr/perl5/vendor_perl/5.8.4/sun4-solaris-64int
    /usr/perl5/vendor_perl/5.8.4
    /usr/perl5/vendor_perl
    .
 
---
Environment for perl v5.8.4:
    HOME=/emc/dheringt
    LANG (unset)
    LANGUAGE (unset)
    LC_COLLATE=en_US.ISO8859-1
    LC_CTYPE=en_US.ISO8859-1
    LC_MESSAGES=C
    LC_MONETARY=en_US.ISO8859-1
    LC_NUMERIC=en_US.ISO8859-1
    LC_TIME=en_US.ISO8859-1
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
 
PATH=.:/emc/dheringt/bin:/usr/local/project/pp/tools/sparc_solaris/bin:/usr/
bin:/usr/local/bin:/usr/ucb:/usr/bin:
    PERL_BADLANG (unset)
    SHELL=/bin/csh

• [perl #37315] 'my' with 'if 0' retains old value by herington, dean
• RE: [perl #37315] 'my' with 'if 0' retains old value by DeRykus, Charles E
• Re: [perl #37315] 'my' with 'if 0' retains old value by Steven Schubiger