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To: internals@lists.php.net, bishop@php.net
Message-ID: <20160805000817.998351A80123@dd1730.kasserver.com>
Date: Fri,  5 Aug 2016 02:08:17 +0200 (CEST)
Subject: Re: [PHP-DEV] Tracing exit()
From: mails@thomasbley.de ("Thomas Bley")

Hi!

having a complete trace from an exception would be great:

function shutdown() {
  $e = new Exception();
  echo $e->getTraceAsString();
}
function test() {
  exit;
}

register_shutdown_function('shutdown');
test();

gives:
#0 [internal function]: shutdown()
#1 {main}

Regards
Thomas


Bishop Bettini wrote on 04.08.2016 20:10:

> Hi!
> 
> exit (and its doppelganger die) is a hard stop to the engine and there is
> little telemetry provided about the circumstances (file, line, message, and
> code). In source I control, exit is no big deal: I don't use exit! But in
> library code, exit can be frustrating.
> 
> register_shutdown_function + debug_backtrace doesn't help, because the
> trace doesn't flow out of the shutdown function. xdebug helps to find the
> exit frame, but cannot pinpoint the exact line. It seems like the engine
> could help with a little extra telemetry.
> 
> I'm wondering if the shutdown functions could access telemetry:
> 
> <?php
> register_shutdown_function(function () {
> 
>    $context = shutdown_get_context();
> 
>    /** array ( 'exit' => array ('file' => '/path/to/Foo.php', 'line' =>
> 242, 'message' => "Calling exit() because...", 'code' => 0)) */
>    // different SAPI may expand on this context
> });
> 
> require 'vendor/autoload.php';
> \Vendor\Package\Class::callsExit();
> ?>
> 
> Or, alternatively, I wonder if a method to convert an exit to an exception
> would be better:
> 
> <?php
> echo ini_get('zend.exit_exception'); // "1"
> 
> try {
>    require 'vendor/autoload.php';
>    \Vendor\Package\Class::callsExit();
> } catch (\ExitException $ex) { // extends \RuntimeException
>    echo 'Stop that!';
> }
> ?>
> 
> (In all these examples, "callsExit" is vendor code that performs an
> undesirable exit();)
> 
> This latter approach feels more modern, at least from a user perspective,
> but it has the side effect of making exit recoverable. IMO, that's a good
> thing, because the conditions under which libraries exit may merely be
> exceptional for consuming applications.
> 
> However, I'm uncertain of an "exit exception" implementation. Perhaps when
> INI enabled, zend_compile_exit could rewrite to emit ZEND_THROW with a
> synthetic node. Or all the ZEND_EXIT could be updated to throw instead of
> bailout. Don't know.
> 
> TL;DR: Engine support for tracing/trapping/debugging exit helps developers
> find and avoid hard exits in dependent code they don't control. Thoughts on
> proceeding with an RFC?
> 
> bishop
>