Re^2: 5.10 shows uninitialized $@ warning

Thank for your post, when I understand it correctly I would recommend the use of eval in a destructor as not so good practice. But the handler in general are not the problem. The code runs without a exception and no handler is called. What I dislike is the warning. I found a way to reproduce the warning (a local $@), but I have no idea where this happend in the program. Here is a longer code snippet which reproduces the warnings:

use warnings;use strict;

package What::Ever;

$@=undef;

$SIG{'__DIE__'} = sub { die "My global die: $@" }

; sub divide { 
  local $SIG{'__DIE__'} = sub { die $@ };
  eval { 
     print STDERR 1/$_[0] , "\n";
  }
}

; { local $@; 
    print STDERR "No exception:\n";
    divide(1);
    print STDERR "Throw...\n";
    divide(0);    
  };

warn $@; # with this the warnings are shown // without none
[download]

but this produces the warning in 5.8 too. So I do not really know what introduces the real problem.

Comment on Re^2: 5.10 shows uninitialized $@ warning Download Code

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Re^3: 5.10 shows uninitialized $@ warning by starbolin (Hermit) on May 16, 2008 at 17:14 UTC
Except I doubt your code snippet is representative of your actual code and thus of little use in the discussion. Reading through the discussion I kept getting confused as to where the problem lay. This is why we need code that is representative of your code and which demonstrates the problem. First, can you verify that your current code runs without warning under 5.8 so that were sure some change didn't slip into the code? Next you're going to have to start paring things from your code until the warning goes away. I'm sorry we can't do this for you. You're going to have to be the one to do this. Once you find the offending bit of code then we can put more that one set of eyes on it and try to determine whether it is the code or whether something's not right in 5.10. pmSwim writes: "The code runs without a exception and no handler is called." Are you sure? The warning is a runtime message. This appears to be confirmed in your latest code snippet as you have to issue warn $@ to generate the message. I guess you could also sprinkle $@=''; throughout your code until the warning goes away. s//----->\t/;$~="JAPH";s//\r<$~~/;{s\|~$~-\|-~$~\|\|\|s \|-$~~\|$~~-\|\|\|s,<$~~,<~$~,,s,~$~>,$~~>,, $\|=1,select$,,$,,$,,1e-1;print;redo}	[reply]
Re^4: 5.10 shows uninitialized $@ warning by pmSwim (Acolyte) on May 16, 2008 at 17:59 UTC
Thanks starbolin, to fix the cause of the problem is for me the the best solution. Your doubts are right. Between my "global" sig `die` handler and the one shown was a place where I make `local $SIG{'__DIE__'};` [download] As I removed this, the real error message occurs from "global" handler and was fixed easily.	[reply] [d/l]
Re^3: 5.10 shows uninitialized $@ warning by ikegami (Patriarch) on May 16, 2008 at 18:52 UTC
when I understand it correctly `{ package Foo; sub new { bless({}, $_[0]) } DESTROY { eval { die "Woof\n"; }; } } eval { my $foo = Foo->new(); die "Meow\n"; }; print($@); # Woof` [download] I would recommend the use of eval in a destructor as not so good practice. There's no alternative. The bad practice is relying on $@ telling you if an exception occurred or not. But the handler in general are not the problem If that's true, you wouldn't have to add `local $SIG{'__DIE__'} = sub { die $@ };` in every `eval`. Seeing as you don't control all the `eval`s in your program, a better solution to your initial problem (your handler misbehaving when you are in an `eval`) is to check `$^S` in the global handler but this produces the warning in 5.8 too. So I do not really know what introduces the real problem. As it should. The `local $@;` restores `$@` to its previous value (undef) once the scope in which `local $@;` resides is exited (no matter how its exited). `$@=undef; { local $@; ... } # $@ is undef here, no matter what "..." is.` [download]	[reply] [d/l] [select]