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POPerl: $SIG{__DIE__}, eval { } and stack trace
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copied!<p>I have a piece of Perl code somewhat like the following (strongly simplified): There are some levels of nested subroutine calls (actually, methods), and some of the inner ones do their own exception handling:</p> <pre><code>sub outer { middle() } sub middle { eval { inner() }; if ( my $x = $@ ) { # caught exception if (ref $x eq 'ARRAY') { print "we can handle this ..."; } else { die $x; # rethrow } } } sub inner { die "OH NOES!" } </code></pre> <p>Now I want to change that code so that it does the following:</p> <ul> <li><p>print a full stack trace for every exception that "bubbles up" all the way to the outermost level (<code>sub outer</code>). Specifically, the stack trace should <strong>not</strong> stop at the first level of "<code>eval { }</code>".</p></li> <li><p>Not having to change the the implementation of any of the inner levels.</p></li> </ul> <p>Right now, the way I do this is to install a localized <code>__DIE__</code> handler inside the <code>outer</code> sub:</p> <pre><code>use Devel::StackTrace; sub outer { local $SIG{__DIE__} = sub { my $error = shift; my $trace = Devel::StackTrace->new; print "Error: $error\n", "Stack Trace:\n", $trace->as_string; }; middle(); } </code></pre> <p>[<strong>EDIT</strong>: I made a mistake, the code above actually <em>doesn't</em> work the way I want, it actually bypasses the exception handling of the <code>middle</code> sub. So I guess the question should really be: Is the behaviour I want even possible?]</p> <p><del>This works perfectly</del>, the only problem is that, if I understand the docs correctly, it relies on behaviour that is explicitly deprecated, namely the fact that <code>__DIE__</code> handlers are triggered even for "<code>die</code>"s inside of "<code>eval { }</code>"s, which they really shouldn't. Both <code>perlvar</code> and <code>perlsub</code> state that this behaviour might be removed in future versions of Perl.</p> <p>Is there another way I can achieve this without relying on deprecated behaviour, or is it save to rely on even if the docs say otherwise?</p>

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