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Date: Fri, 3 Sep 2021 17:15:49 +0100
Message-ID: <CADJ56BRYYFx6w=88m+=XYX7xXNQR=N27DhE9q_3yKb2F2doTwQ@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Christian Schneider <cschneid@cschneid.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Adding a way to disable the stat cache
From: kevin@lyda.ie (Kevin Lyda)

On Fri, Sep 3, 2021 at 4:24 PM Nikita Popov <nikita.ppv@gmail.com> wrote:
> Just to throw it out there: Maybe we should clear the stat cache when fun=
ctions in the exec family are used? Even if we allow disabling the stat cac=
he, I think we can easily avoid that particular footgun. And if calls to ex=
ternal binaries are involved we likely don't have to worry about stat overh=
ead.

This code also breaks:

<?php

$testfile=3D 'bug28790.write.out';

function print_stat($filename) {
    $s =3D @stat($filename);
    echo "$filename: ".$s['size']."\n";
}

$f =3D fopen($testfile, "a");
print_stat($testfile);
fwrite($f, "five\n");
print_stat($testfile);
fclose($f);

So you'd need to add fwrite and a number of other functions to the ones man=
aging
this cache. And after all that, external programs (or forked children)
can ruin your
day. One could argue that making a bug more arcane is a form of cruelty.

Kevin