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From: Ayush Tiwari <ayushtiwari.slg01@gmail.com>
Date: Fri, 15 May 2026 09:12:11 +0530
Message-ID: 
 <CAJTYsWVg5j_UA8mcNTWcQnhePxyd_DLZT7QDQv54dvcG=900Jg@mail.gmail.com>
Subject: Re: Add a guard against uninitialized default locale
To: Jeff Davis <pgsql@j-davis.com>
Cc: pgsql-hackers@postgresql.org
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Hi,

On Fri, 15 May 2026 at 03:30, Jeff Davis <pgsql@j-davis.com> wrote:

> On Fri, 2026-04-24 at 15:44 -0700, Jeff Davis wrote:
> > Not known to be reachable after dbf217c1c7, but defend against
> > similar
> > issues in the future. For instance, an extension might encounter the
> > problem by calling pg_newlocale_from_collation(DEFAULT_COLLATION_OID)
> > from _PG_init(), and end up with a NULL pointer dereference.
> >
> > Backport through 17, though patch is different in 17 (also attached).
>
> I plan to commit and backport this soon.
>
>
The patch looks good to me as it is.

Just one nit in PG 17 patch:

   The provider == '\0' sentinel is correct (valid
   providers are 'b'/'c'/'i'/'d', all nonzero) and the three guarded
   sites (lc_collate_is_c, lc_ctype_is_c, pg_newlocale_from_collation)
   cover the direct consumers symmetrically.  The only thing maybe
   consider is replacing the bare /* should not happen */ above the
   '\0' test with something like /* provider unset; init_database_-
   collation() not yet run */ -- the literal '\0' check reads as a bit
   magical otherwise, but maybe you are doing that to have same
   comment throughout.

Regards,
Ayush

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<div dir=3D"ltr"><div dir=3D"ltr">Hi,</div><br><div class=3D"gmail_quote gm=
ail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Fri, 15 May 2=
026 at 03:30, Jeff Davis &lt;<a href=3D"mailto:pgsql@j-davis.com">pgsql@j-d=
avis.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D=
"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-le=
ft:1ex">On Fri, 2026-04-24 at 15:44 -0700, Jeff Davis wrote:<br>
&gt; Not known to be reachable after dbf217c1c7, but defend against<br>
&gt; similar<br>
&gt; issues in the future. For instance, an extension might encounter the<b=
r>
&gt; problem by calling pg_newlocale_from_collation(DEFAULT_COLLATION_OID)<=
br>
&gt; from _PG_init(), and end up with a NULL pointer dereference.<br>
&gt; <br>
&gt; Backport through 17, though patch is different in 17 (also attached).<=
br>
<br>
I plan to commit and backport this soon.<br><br></blockquote><div><br></div=
><div>The patch looks good to me as it is.</div><div><br></div><div>Just on=
e nit in PG 17 patch:<br><br>=C2=A0 =C2=A0The provider =3D=3D &#39;\0&#39; =
sentinel is correct (valid<br>=C2=A0 =C2=A0providers are &#39;b&#39;/&#39;c=
&#39;/&#39;i&#39;/&#39;d&#39;, all nonzero) and the three guarded<br>=C2=A0=
 =C2=A0sites (lc_collate_is_c, lc_ctype_is_c, pg_newlocale_from_collation)<=
br>=C2=A0 =C2=A0cover the direct consumers symmetrically.=C2=A0 The only th=
ing maybe<br>=C2=A0 =C2=A0consider is replacing the bare /* should not happ=
en */ above the<br>=C2=A0 =C2=A0&#39;\0&#39; test with something like /* pr=
ovider unset; init_database_-<br>=C2=A0 =C2=A0collation() not yet run */ --=
 the literal &#39;\0&#39; check reads as a bit<br>=C2=A0 =C2=A0magical othe=
rwise, but maybe you are doing that to have same</div><div>=C2=A0 =C2=A0com=
ment throughout.</div></div><div class=3D"gmail_quote gmail_quote_container=
"><br></div><div class=3D"gmail_quote gmail_quote_container">Regards,<br>Ay=
ush</div></div>

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