From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Thai <thomas.t.thai@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: PostgreSQL 18 beta1 - Segmentation fault on custom type casting
Date: Thu, 10 Jul 2025 10:55:13 -0400
Message-ID: <1525420.1752159313@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+ywuyaRRX6N5Kh16vMWoXEJxct+fEKQCk-8OKUswepYi2r-yg@mail.gmail.com>
References: <CA+ywuyaRRX6N5Kh16vMWoXEJxct+fEKQCk-8OKUswepYi2r-yg@mail.gmail.com>
Thomas Thai <thomas.t.thai@gmail.com> writes:
> PostgreSQL 18 beta crashes with a segmentation fault when casting strings
> to custom types. The crash occurs specifically in PostgreSQL's type-casting
> system, not in extension code.
The reason you're having a problem is that this is not a valid way to
store a custom type. The representation has to be a single blob of
memory [1], and it has to be represented in a way that lets
type-independent code determine its length. Typically that means
following the varlena-header rules.
regards, tom lane
[1] Well, there is a notion of an "expanded" representation that
doesn't have to be a flat blob. But you're not following the
rules for that either.
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, thomas.t.thai@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: PostgreSQL 18 beta1 - Segmentation fault on custom type casting
In-Reply-To: <1525420.1752159313@sss.pgh.pa.us>
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