From ambrus@math.bme.hu

Created by ambrus@math.bme.hu

After the statements '*x=*y; @x=8; @y=@x;', the array @x should still
contain a single element whose value is 8. In all perl versions I tried,
this leaves a single element in @x that is undefined, which is definitely an
incorrect result. Further, some older perl versions give a semi-panic
warning.

$ perl5.12.2 -we '*x=*y; @x=8; @y=@x; warn @x;'
semi-panic: attempt to dup freed string at -e line 1.
Use of uninitialized value within @x in warn at -e line 1.
Warning: something's wrong at -e line 1.
$ perl5.13.11 -we '*x=*y; @x=8; @y=@x; warn @x;'
Use of uninitialized value $x[0] in warn at -e line 1.
Warning: something's wrong at -e line 1.

Perl 5.14.0RC1 still behaves the same as 5.13.11: $x[0] becomes undefined,
but there's no semi-panic.

Thanks,

Ambrus

Perl Info


Flags:
    category=core
    severity=low

Site configuration information for perl 5.12.3:

Configured by ambrus at Tue Jan 25 14:12:12 CET 2011.

Summary of my perl5 (revision 5 version 12 subversion 3) configuration:

  Platform:
    osname=linux, osvers=2.6.34.1, archname=x86_64-linux
    uname='linux king 2.6.34.1 #1 smp sat jul 10 18:21:56 cest 2010
x86_64 gnulinux '
    config_args='-Dinc_version_list=5.12.2/x86_64-linux 5.12.2
5.12.1/x86_64-linux 5.12.1 5.12.0/x86_64-linux 5.12.0 -d'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-strict-aliasing -pipe -fstack-protector
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2',
    cppflags='-fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
    ccversion='', gccversion='4.5.1', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    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 -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64 /usr/local/lib64
    libs=-lnsl -ldl -lm -lcrypt -lutil -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=/lib/libc-2.7.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.7'
  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'

Locally applied patches:



@INC for perl 5.12.3:
    /usr/local/lib/perl5/site_perl/5.12.3/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.12.3
    /usr/local/lib/perl5/5.12.3/x86_64-linux
    /usr/local/lib/perl5/5.12.3
    /usr/local/lib/perl5/site_perl/5.12.2/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.12.2
    /usr/local/lib/perl5/site_perl/5.12.1/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.12.1
    /usr/local/lib/perl5/site_perl/5.12.0/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.12.0
    /usr/local/lib/perl5/site_perl
    .


Environment for perl 5.12.3:
    HOME=/home/ambrus
    LANG (unset)
    LANGUAGE (unset)
    LC_CTYPE=hu_HU
    LD_LIBRARY_PATH=/home/ambrus/local/lib/
    LOGDIR (unset)
    PATH=/home/ambrus/local/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games
    PERL_BADLANG (unset)
    SHELL=/usr/local/bin/bash

Uh oh!

exchange value of $a,$b without $temporary variable #5788

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