| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Thomas Thai <thomas(dot)t(dot)thai(at)gmail(dot)com> |
| Cc: | pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: PostgreSQL 18 beta1 - Segmentation fault on custom type casting |
| Date: | 2025-07-10 14:55:13 |
| Message-ID: | 1525420.1752159313@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
Thomas Thai <thomas(dot)t(dot)thai(at)gmail(dot)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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