in reply to Re3: How to detect a die() without catching it?
in thread How to detect a die() without catching it?

Mid-air collision of update and reply! Eee gads. Ok, I see what you mean about not needing to die() from &$SIG{__DIE__}. (Although, BTW, this recursion isn't "bad" - it's actually recommended in the die() docs as the way to change the error message!)

But I think my concern about the call stack still stands. How can a single global handler be enough?

UPDATE: To clarify, here's an example of how $SIG{__DIE__} doesn't behave the way I think I would need it to: 

sub catcher {
    local $SIG{__DIE__} = sub { print "Caught 1!\n"; };
    catcher2();
}

sub catcher2 {
    local $SIG{__DIE__} = sub { print "Caught 2!\n"; };
    sub_that_dies();
}

sub sub_that_dies {
    die "Foo";
}

catcher();

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Now, I'd like that code to print both "Caught 1!" and "Caught 2!". But what it actually does is less useful: 

$ perl bomb.pl 
Caught 2!
Foo at bomb.pl line 30.

[download]

Does that make it clear what I mean?

-sam

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Re: Re: Re3: How to detect a die() without catching it?
by belg4mit (Prior) on May 17, 2002 at 23:37 UTC
    Well I was a bit hasty in calling it recursion, as it isn't really.

    So actually you want the opposite (in a manner of speaking) of what you said, you wish to artificially enforce inheritance of die as *exceptions*. The code you give does exactly what it is supposed to, there is no die called within catcher, and $SIG{__DIE__} is re-localed to the catcher2 scope.

    I think Exception::Class is what you want for that. Alternatively, here's some ugly code 

    local @stack;
$SIG{__DIE__} = sub { die(@stack, @_); };
catcher();

sub catcher {
    local @stack = (@stack, "Caught 1!\n");
    catcher2();
}

sub catcher2 {
    local @stack = (@stack, "Caught 2!\n");
    sub_that_dies();
}

sub sub_that_dies {
    die "Foo";
}

    [download]

    If, on the other hand, you actually want what's in yor original code, which is just to do something before (outter) dieing then I stand by the original suggestions, and also add END to the list; END output comes last though. 

    #=begin a
require 'b';
print "Hello World\n";
#This die can also be replaced with print && exit
$SIG{__DIE__} = sub { print "BOB!\n"; die(@_); };
a::a();
END{ print "Waka waka\n";
#=end a
#=begin b
package a;
sub a{
die("A!"); }
1;
#=end b
__END__
Hello World
BOB!
A! at /tmp/b line 3.
Waka waka

    [download]

    --
    perl -pew "s/\b;([mnst])/'$1/g"

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[d/l]
[select]
      You're probably correct that what I want are exceptions, but I don't think I can get them. I'm writing a profiler and it's supposed to work with a wide range of code, most of which will be using straight die()s.

      Thanks for the help!
      -sam

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