From @jimav

An exception thrown from a tied variable handler can not be caught.
The application is unconditionally terminated.
At least so it seems!

If true, it is a severe limitation on the possible robustness
of applications which use tied variables to access something
which might encounter an error or timeout.

#!/usr/bin/perl
use strict; use warnings;

package Tie​::MyTie;
sub TIESCALAR { my $class=shift; return bless [], $class; }
sub FETCH { die "FETCH throwing an error" }

package main;

our $x;
tie $x, 'Tie​::MyTie', 42;

# This eval should catch the exception, no?
my $val = eval '$x'; # dies here (really dead)
warn "caught exception​:$@​" if $@​;

warn "Expecting to get here\n";

Flags​:
  category=core
  severity=medium

Site configuration information for perl 5.14.2​:

Configured by Debian Project at Fri Aug 10 21​:43​:06 UTC 2012.

Summary of my perl5 (revision 5 version 14 subversion 2) configuration​:
 
  Platform​:
  osname=linux, osvers=2.6.42-26-generic, archname=x86_64-linux-gnu-thread-multi
  uname='linux allspice 2.6.42-26-generic #41-ubuntu smp thu jun 14 17​:49​:24 utc 2012 x86_64 x86_64 x86_64 gnulinux '
  config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.14 -Darchlib=/usr/lib/perl/5.14 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.14.2 -Dsitearch=/usr/local/lib/perl/5.14.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.14.2 -des'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=define, usemultiplicity=define
  useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
  use64bitint=define, use64bitall=define, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
  optimize='-O2 -g',
  cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing -pipe -fstack-protector -I/usr/local/include'
  ccversion='', gccversion='4.6.3', 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/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /usr/lib
  libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
  perllibs=-ldl -lm -lpthread -lc -lcrypt
  libc=, so=so, useshrplib=true, libperl=libperl.so.5.14.2
  gnulibc_version='2.15'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
  cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib -fstack-protector'

Locally applied patches​:
 

@​INC for perl 5.14.2​:
  /home/jima/local/lib/perl/5.14.2
  /home/jima/local/lib/perl
  /home/jima/local/share/perl/5.14.2
  /home/jima/local/share/perl
  /home/jima/lib/perl
  /etc/perl
  /usr/local/lib/perl/5.14.2
  /usr/local/share/perl/5.14.2
  /usr/lib/perl5
  /usr/share/perl5
  /usr/lib/perl/5.14
  /usr/share/perl/5.14
  /usr/local/lib/site_perl
  .

Environment for perl 5.14.2​:
  HOME=/home/jima
  LANG=en_US.UTF-8
  LANGUAGE=
  LD_LIBRARY_PATH=/home/jima/local/lib
  LOGDIR (unset)
  PATH=/home/jima/bin​:/home/jima/local/bin​:/home/jima/jima_tools/bin​:/opt/libreoffice3.6/program​:/usr/bin​:/bin​:/usr/sbin​:/sbin​:/usr/bin/X11​:/usr/local/bin​:/usr/local/sbin​:/usr/games​:.
  PERL5LIB=/home/jima/local/lib/perl​:/home/jima/local/share/perl​:/home/jima/lib/perl
  PERL_BADLANG (unset)
  SHELL=/bin/bash

From @cpansprout

On Thu Aug 30 21​:45​:36 2012, jimav wrote​:

-----------------------------------------------------------------
An exception thrown from a tied variable handler can not be caught.
The application is unconditionally terminated.
At least so it seems!

If true, it is a severe limitation on the possible robustness
of applications which use tied variables to access something
which might encounter an error or timeout.

#!/usr/bin/perl
use strict; use warnings;

package Tie​::MyTie;
sub TIESCALAR { my $class=shift; return bless [], $class; }
sub FETCH { die "FETCH throwing an error" }

package main;

our $x;
tie $x, 'Tie​::MyTie', 42;

# This eval should catch the exception, no?
my $val = eval '$x'; # dies here (really dead)
warn "caught exception​:$@​" if $@​;

warn "Expecting to get here\n";

Try​:

  my $val;
  eval '$val = $x';

The eval is returning the $x itself, and the assignment outside the eval
is calling FETCH.

However, there is something fishy going on, as eval does appear to
return a different value here​:

$ perl -le' print \$x; print \do{$x}; print \eval{$x}; print \eval q|$x|'
SCALAR(0x826d90)
SCALAR(0x826d90)
SCALAR(0x8039f0)
SCALAR(0x826db0)

So I suspect something needs fixing, but I’m not sure exactly what.

This may be related to #105910.

--

Father Chrysostomos

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