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[perl #57500] Passing object around affects += overloading
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From:
Peter Scott
Date:
August 2, 2008 04:31
Subject:
[perl #57500] Passing object around affects += overloading
Message ID:
rt-3.6.HEAD-29759-1217553044-1755.57500-75-0@perl.org
# New Ticket Created by Peter Scott
# Please include the string: [perl #57500]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=57500 >
This occurs on at least 5.8.8 and 5.10.0. Make two objects from a
package with += overloaded (and nothing else), then += them. If you do
that directly after construction, no problem. If you do that after
passing the objects through some intermediate assignment, e.g. as hash
values, the runtime error
Operation "=": no method found, argument in overloaded package
is emitted.
--cut--
my $bar_x = Bar->new;
my $bar_y = Bar->new;
# No problem:
$bar_x += $bar_y; # 42
my $x = { bar => Bar->new };
my $y = { bar => Bar->new };
my $der_x = $x->{bar};
my $der_y = $y->{bar};
# Operation "=": no method found, argument in overloaded package Bar:
$der_x += $der_y;
package Bar;
use overload '+=' => sub { 42 };
sub new { return bless {}, shift }
__END__
The objects $bar_x and $der_x look identical (pace addresses) under
Devel::Peek, and -Do prints exactly the same thing before each +=
operation. If this behavior is mentioned anywhere online or in
overload.pm documentation it eludes me. Workaround appears to be to add
'=' => sub { shift }
to the overload.
Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
Platform:
osname=linux, osvers=2.6.16-1.2133_fc5, archname=i686-linux
uname='linux tweety 2.6.16-1.2133_fc5 #1 tue jun 6 00:52:14 edt
2006 i686 athlon i386 gnulinux '
config_args='-des -DDEBUGGING'
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
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
-I/usr/include/gdbm',
optimize='-O2 -g',
cppflags='-DDEBUGGING -fno-strict-aliasing -pipe
-I/usr/local/include -I/usr/include/gdbm'
ccversion='', gccversion='4.1.1 20060525 (Red Hat 4.1.1-1)',
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 =' -L/usr/local/lib'
libpth=/usr/local/lib /lib /usr/lib
libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc
perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
libc=/lib/libc-2.4.so, so=so, useshrplib=false, libperl=libperl.a
gnulibc_version='2.4'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib'
Characteristics of this binary (from libperl):
Compile-time options: DEBUGGING PERL_DONT_CREATE_GVSV PERL_MALLOC_WRAP
USE_LARGE_FILES USE_PERLIO
Built under linux
Compiled at Dec 26 2007 19:03:58
@INC:
/usr/local/lib/perl5/5.10.0/i686-linux
/usr/local/lib/perl5/5.10.0
/usr/local/lib/perl5/site_perl/5.10.0/i686-linux
/usr/local/lib/perl5/site_perl/5.10.0
/usr/local/lib/perl5/site_perl/5.8.8
/usr/local/lib/perl5/site_perl
.
--
Peter Scott
Pacific Systems Design Technologies
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[perl #57500] Passing object around affects += overloading
by Peter Scott