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 <CAMW7n8CNTwOtsUbAbH-0Kk1Ck3DZ1fKF=P9GfctwDk9KmCr2XQ@mail.gmail.com> <64f44c6f-a1ef-4a26-9063-d4d90fdf678c@app.fastmail.com>
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Date: Sun, 27 Apr 2025 20:12:35 +0300
Message-ID: <CAMW7n8CY-d=8MG5663AbuWqyuK8=tRLgksnv3PbHwDy-VZ_aow@mail.gmail.com>
Subject: Re: [PHP-DEV] Concept: Lightweight error channels
To: Rob Landers <rob@bottled.codes>
Cc: Larry Garfield <larry@garfieldtech.com>, php internals <internals@lists.php.net>
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From: edmond.ht@gmail.com (Edmond Dantes)

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The HHVM project suggests an interesting Lazy backtrace generation
mechanism based on stack unwinding.


   1.

   An exception is generated.
   2.

   The stack enters an unwinding mode. In this mode, PHP gradually collects
   information into the backtrace.
   3.

   Each frame exit contributes a part of the backtrace.
   4.

   Once the exception is caught, the unwinding process stops.
   5.

    Now a decision can be made: either generate the full backtrace or
   suppress the exception.


Advantages:

   1.

   Allows deferring backtrace generation until the exception is caught.
   2.

   Allows suppressing exceptions without a backtrace, making their creation
   cost cheap.
   3.

   Allows preserving exceptions with a backtrace only when necessary.

Disadvantages: requires added complexity.

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<div dir=3D"ltr"><div dir=3D"ltr"><p class=3D"gmail-">The HHVM project sugg=
ests an interesting Lazy backtrace generation mechanism based on stack unwi=
nding.</p><p class=3D"gmail-">
</p><ol>
<li class=3D"gmail-">
<p class=3D"gmail-">An exception is generated.</p>
</li>
<li class=3D"gmail-">
<p class=3D"gmail-">The stack enters an unwinding mode. In this mode, PHP g=
radually collects information into the backtrace.</p>
</li>
<li class=3D"gmail-">
<p class=3D"gmail-">Each frame exit contributes a part of the backtrace.</p=
>
</li>
<li class=3D"gmail-">
<p class=3D"gmail-">Once the exception is caught, the unwinding process sto=
ps.</p></li><li class=3D"gmail-"><p class=3D"gmail-">=C2=A0Now a decision c=
an be made: either generate the full backtrace or suppress the exception.</=
p></li></ol>=C2=A0=C2=A0</div><div dir=3D"ltr">Advantages:<div>
<ol>
<li class=3D"gmail-">
<p class=3D"gmail-">Allows deferring backtrace generation until the excepti=
on is caught.</p>
</li>
<li class=3D"gmail-">
<p class=3D"gmail-">Allows suppressing exceptions without a backtrace, maki=
ng their creation cost cheap.</p>
</li>
<li class=3D"gmail-">
<p class=3D"gmail-">Allows preserving exceptions with a backtrace only when=
 necessary.</p>
</li>
</ol>
<p class=3D"gmail-">Disadvantages: requires added complexity.</p></div></di=
v></div>

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