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Date: Wed, 29 May 2024 19:05:57 +0100 (BST)
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>
cc: Ilija Tovilo <tovilo.ilija@gmail.com>, 
    PHP internals <internals@lists.php.net>
Subject: Re: [PHP-DEV] [RFC] Transform exit() from a language construct into
 a standard function
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From: derick@php.net (Derick Rethans)

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On Tue, 28 May 2024, Tim D=C3=BCsterhus wrote:

> On 5/28/24 16:26, Derick Rethans wrote:
>
> > I have just checked this for Xdebug, and you're definitely right=20
> > with that. With the removal of the ZEND_EXIT opcode, it can not now=20
> > detect a scope/function exit now.
>=20
> Can you clarify why ZEND_EXIT is special for Xdebug when compared to=20
> any other function that unconditionally throws or unconditionally=20
> calls exit(); by itself, i.e. any other function with a `never` return=20
> type?

For each op_array, Xdebug tries to figure out every possible path by=20
following jumps. Certain opcodes, such as GENERATOR_RETURN, THROW,=20
RETURN, and EXIT [1] are considered as an exit point out of the=20
function. A path ends there.

If there is a function call to a function with a 'never' return type,=20
then that function will potentially throw, or exit.

But that's not relevant for the analysis, as these userland functions=20
will have their own oparrays with their entry and exit points.

I can't through this mechanism know when an *internal* function does=20
something similar, as it looks like just a normal function call (unless=20
I hard code the check for a call to 'exit').

[1] https://github.com/xdebug/xdebug/blob/master/src/coverage/code_coverage=
=2Ec#L348

> > It also breaks my "do tasks on ZEND_EXIT" with the profiler. It is=20
> > used to always write the closing profiling footer to the files.=20
> > Without me being able to overload thati opcode, data would not be=20
> > complete. I even have two bugs (with tests) for this:
> >=20
> > - https://bugs.xdebug.org/68
> > - https://bugs.xdebug.org/631
>=20
> Likewise, how is ZEND_EXIT special here? How does it work differently tha=
n a
> script that runs to completion without calling exit(); or a script that f=
ails,
> e.g. due to an uncaught exception or due to reaching the memory limit?

I overload EXIT so that I can flush the profile file before the script=20
actually fully ends. This is useful for testing through phpt tests. It=20
looks like I might be able to use existing function observers for this,=20
but I haven't fully made that work yet.

cheers,
Derick

--=20
https://derickrethans.nl | https://xdebug.org | https://dram.io

Author of Xdebug. Like it? Consider supporting me: https://xdebug.org/suppo=
rt

mastodon: @derickr@phpc.social @xdebug@phpc.social
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