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Re: Bug in eval in pre-5.14

by $h4X4_|=73}{ (Monk)
on Aug 13, 2016 at 15:27 UTC ( [id://1169712]=note: print w/replies, xml ) Need Help??


in reply to Bug in eval in pre-5.14

When I add control over die() and exit() I can make the code stop right at the first die on any version. Tested on 5.8 and 5.22.

#!/usr/bin/perl use warnings; use strict; BEGIN { # control eval's bypass of die $SIG{__DIE__} = \&Splacker; } print $], "\n"; { package My::Obj; sub new { my $class = shift; bless {@_}, $class } sub DESTROY { my $self = shift; eval { 1 } if ! $self->{finished}; } } my $o1 = 'My::Obj'->new(finished => 1); undef $o1; # Exception overlooked. eval { my $o2 = 'My::Obj'->new; die "Exception!"; }; if ($@) { warn "Caught with \$\@: $@"; } # Exception details lost. eval { my $o2 = 'My::Obj'->new; die "Exception!"; 1 } or do { warn "Caught with or: $@"; }; # Same as above. use Try::Tiny; try { my $o3 = 'My::Obj'->new; die "Exception!"; } catch { warn "Caught with Try::Tiny: $_"; }; sub Splacker { my $error = shift; print $error; CORE::exit(1); }

Output:
5.008008 Exception! at C:\xampp\cgi-bin\Test\tester.pl line 32.


Update: And if you comment out CORE::exit(1); the output is.
Caught with or: at C:\xampp\cgi-bin\Test\tester.pl line 44. Caught with Try::Tiny: at C:\xampp\cgi-bin\Test\tester.pl line 55. 5.008008 Exception! at C:\xampp\cgi-bin\Test\tester.pl line 32. Exception! at C:\xampp\cgi-bin\Test\tester.pl line 42. Exception! at C:\xampp\cgi-bin\Test\tester.pl line 53.

Update 2: Forgot about STDERR. If used in print like so.
sub Splacker { my $error = shift; print STDERR $error; }

The Output is...
Exception! at C:\xampp\cgi-bin\Test\tester.pl line 32. Exception! at C:\xampp\cgi-bin\Test\tester.pl line 42. Caught with or: at C:\xampp\cgi-bin\Test\tester.pl line 44. Exception! at C:\xampp\cgi-bin\Test\tester.pl line 53. Caught with Try::Tiny: at C:\xampp\cgi-bin\Test\tester.pl line 55. 5.008008

Replies are listed 'Best First'.
Re^2: Bug in eval in pre-5.14
by choroba (Cardinal) on Aug 13, 2016 at 17:59 UTC
    The point of try/catch is not to stop on the first error (or print it), but to process it and decide to rethrow or continue.

    ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord }map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

      With a little tweaking of the code it can be done. I was playing around with it so there is more code in Splacker then needed.

      #!/usr/bin/perl use warnings; use strict; BEGIN { # control eval's bypass of die $SIG{__DIE__} = \&Splacker; } my $error_log = ''; print $], "\n"; { package My::Obj; sub new { my $class = shift; bless {@_}, $class } sub DESTROY { my $self = shift; eval { 1 } if ! $self->{finished}; } } my $o1 = 'My::Obj'->new(finished => 1); undef $o1; # Exception Found. eval { my $o2 = 'My::Obj'->new; die "Exception 0!"; }; # And Caught if (Splacker()) { warn 'Caught with Splacker: '.Splacker(); } # Give back die control if you want... $SIG{__DIE__} = \&CORE::die; # Exception overlooked. eval { my $o2 = 'My::Obj'->new; die "Exception 1!"; }; if ($@) { warn "Caught with \$\@: $@"; } # Exception details lost. eval { my $o2 = 'My::Obj'->new; die "Exception 2!"; 1 } or do { warn "Caught with or: $@"; }; # Same as above. use Try::Tiny; try { my $o3 = 'My::Obj'->new; die "Exception 3!"; } catch { warn "Caught with Try::Tiny: $_"; }; sub Splacker { my $error = shift || ''; if ($error eq 'DIE') { print STDERR $error.' '.$error_log; CORE::exit(1); } elsif ($error) { $error_log = $error; # print STDERR $error; } else { return $error_log; } }
      Output:
      Caught with Splacker: Exception 0! at C:\xampp\cgi-bin\Test\tester.pl +line 33. Caught with or: at C:\xampp\cgi-bin\Test\tester.pl line 56. Caught with Try::Tiny: at C:\xampp\cgi-bin\Test\tester.pl line 67. 5.008008

        OK, and now change {1} in the object's destructor to { die 'inside' } - all other cases still catch the Exception #, but Splacker catches the inner one.

        ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord }map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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