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[perl #21979] Modifying an alias to a read-only item of an argument list of a subroutine works, while it's expected to fail

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From:
perlbug-followup
Date:
April 16, 2003 18:39
Subject:
[perl #21979] Modifying an alias to a read-only item of an argument list of a subroutine works, while it's expected to fail
Message ID:
rt-21979-55284.17.4791040781834@bugs6.perl.org
# New Ticket Created by  trivizki@bigfoot.com 
# Please include the string:  [perl #21979]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=21979 >


This is a bug report for perl from trivizki@bigfoot.com,
generated with the help of perlbug 1.34 running under perl v5.8.0.

sub subname{
 *_=\$_[0];
 s///;
}
subname("string");


Runs with no errors and even modifies $_, although it should not run, as it tries to modify
An alias to (an alias to) a read only value.
Actually, the above should give exactly the same error message the code below gives:

sub subname{
 $_[0]=~s///;
}
subname("string");

"Modification of a read-only value attempted" as the codes should act the same - $_ is just an
alias to $_[0].

Perl 5.6.1 behaved as I expected, while 5.8 did run the code on my system as well as 
on a friend's who's running a *nix based system(Mandrake).

Thanks,
Ido
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl v5.8.0:

Configured by ActiveState at Tue Feb  4 18:07:44 2003.

Summary of my perl5 (revision 5 version 8 subversion 0) configuration:
  Platform:
    osname=MSWin32, osvers=4.0, archname=MSWin32-x86-multi-thread
    uname=''
    config_args='undef'
    hint=recommended, useposix=true, d_sigaction=undef
    usethreads=undef use5005threads=undef useithreads=define usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cl', ccflags ='-nologo -Gf -W3 -MD -Zi -DNDEBUG -O1 -DWIN32 -D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT  -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -DPERL_MSVCRT_READFIX',
    optimize='-MD -Zi -DNDEBUG -O1',
    cppflags='-DWIN32'
    ccversion='', gccversion='', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='__int64', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='link', ldflags ='-nologo -nodefaultlib -debug -opt:ref,icf  -libpath:"C:\Perl\lib\CORE"  -machine:x86'
    libpth="C:\Perl\lib\CORE"
    libs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib  comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib  netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  version.lib odbc32.lib odbccp32.lib msvcrt.lib
    perllibs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib  comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib  netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  version.lib odbc32.lib odbccp32.lib msvcrt.lib
    libc=msvcrt.lib, so=dll, useshrplib=yes, libperl=perl58.lib
    gnulibc_version='undef'
  Dynamic Linking:
    dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
    cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -debug -opt:ref,icf  -libpath:"C:\Perl\lib\CORE"  -machine:x86'

Locally applied patches:
    ACTIVEPERL_LOCAL_PATCHES_ENTRY

---
@INC for perl v5.8.0:
    C:/Perl/lib
    C:/Perl/site/lib
    .

---
Environment for perl v5.8.0:
    HOME (unset)
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=C:\Program Files\Borland\Delphi7\Bin;C:\Program Files\Borland\Delphi7\Projects\Bpl\;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program Files\Common Files\Ulead Systems\MPEG;C:\Perl\bin
    PERL_BADLANG (unset)
    SHELL (unset)



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