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Date: Mon, 05 Aug 2024 21:02:39 +0200
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>,
 "Derick Rethans" <derick@php.net>
Cc: "Ilija Tovilo" <tovilo.ilija@gmail.com>,
 "PHP internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Transform exit() from a language construct into a standard
 function
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From: rob@bottled.codes ("Rob Landers")

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On Mon, Aug 5, 2024, at 19:03, Tim D=C3=BCsterhus wrote:
> >>> If there is a function call to a function with a 'never' return
> >>> type, then that function will potentially throw, or exit.
> >>>
> >>> But that's not relevant for the analysis, as these userland
> >>> functions will have their own oparrays with their entry and exit
> >>> points.
> >>
> >> The compiler has the function table available. It is used to optimi=
ze
> >> specific functions into dedicated Opcodes. Thus you should be able =
to
> >> look up the function within the function table and then check its
> >> return type.
> >=20
> > Yes, but functions that call exit are not required to have the 'neve=
r'
> > return type, so that's not useful.
>=20
> The `exit()` function as implemented in Gina's PR has the `never` retu=
rn=20
> type, thus the situation is no worse than the current situation. Inste=
ad=20
> of checking for the ZEND_EXIT opcode, you check for a function call an=
d=20
> if the function has the `never` return type (which `exit()` is=20
> guaranteed to have), then you can treat it as a path ending there. Or=20
> you can just hardcode a check for a call to the `exit()` function, as=20
> outlined above.

Just to clarify: a never return type doesn't mean execution ends there.

throwing:
https://3v4l.org/s3KDM

infinite loop:
https://3v4l.org/Lpbtt

=E2=80=94 Rob
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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}</style></head><body><div><br></div><div>=
<br></div><div>On Mon, Aug 5, 2024, at 19:03, Tim D=C3=BCsterhus wrote:<=
br></div><blockquote type=3D"cite" id=3D"qt" style=3D""><div>&gt;&gt;&gt=
; If there is a function call to a function with a 'never' return<br></d=
iv><div>&gt;&gt;&gt; type, then that function will potentially throw, or=
 exit.<br></div><div>&gt;&gt;&gt;<br></div><div>&gt;&gt;&gt; But that's =
not relevant for the analysis, as these userland<br></div><div>&gt;&gt;&=
gt; functions will have their own oparrays with their entry and exit<br>=
</div><div>&gt;&gt;&gt; points.<br></div><div>&gt;&gt;<br></div><div>&gt=
;&gt; The compiler has the function table available. It is used to optim=
ize<br></div><div>&gt;&gt; specific functions into dedicated Opcodes. Th=
us you should be able to<br></div><div>&gt;&gt; look up the function wit=
hin the function table and then check its<br></div><div>&gt;&gt; return =
type.<br></div><div>&gt;&nbsp;<br></div><div>&gt; Yes, but functions tha=
t call exit are not required to have the 'never'<br></div><div>&gt; retu=
rn type, so that's not useful.<br></div><div><br></div><div>The `exit()`=
 function as implemented in Gina's PR has the `never` return&nbsp;<br></=
div><div>type, thus the situation is no worse than the current situation=
. Instead&nbsp;<br></div><div>of checking for the ZEND_EXIT opcode, you =
check for a function call and&nbsp;<br></div><div>if the function has th=
e `never` return type (which `exit()` is&nbsp;<br></div><div>guaranteed =
to have), then you can treat it as a path ending there. Or&nbsp;<br></di=
v><div>you can just hardcode a check for a call to the `exit()` function=
, as&nbsp;<br></div><div>outlined above.<br></div></blockquote><div><br>=
</div><div>Just to clarify: a never return type doesn't mean execution e=
nds there.<br></div><div><br></div><div>throwing:</div><div><a href=3D"h=
ttps://3v4l.org/s3KDM">https://3v4l.org/s3KDM</a><br></div><div><br></di=
v><div>infinite loop:</div><div><a href=3D"https://3v4l.org/Lpbtt">https=
://3v4l.org/Lpbtt</a><br></div><div><br></div><div id=3D"sig121229152">=E2=
=80=94 Rob<br></div></body></html>
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