Horton

Fix various instances of undefined behavior

John Naylor <john.naylor@postgresql.org>

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Commit: 176dffdf7d2a0ea2615c4e390a2ab7e69d14f90f
Author: John Naylor <john.naylor@postgresql.org>
Date: 2026-02-04T11:09:35Z
Releases: 19 (unreleased) 
Fix various instances of undefined behavior

Mostly this involves checking for NULL pointer before doing operations
that add a non-zero offset.

The exception is an overflow warning in heap_fetch_toast_slice(). This
was caused by unneeded parentheses forcing an expression to be
evaluated to a negative integer, which then got cast to size_t.

Per clang 21 undefined behavior sanitizer.

Backpatch to all supported versions.

Co-authored-by: Alexander Lakhin <exclusion@gmail.com>
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/777bd201-6e3a-4da0-a922-4ea9de46a3ee@gmail.com
Backpatch-through: 14

Files

PathChange+/−
contrib/pg_trgm/trgm_gist.c modified +4 −1
src/backend/access/heap/heaptoast.c modified +1 −1
src/backend/utils/adt/multirangetypes.c modified +3 −2
src/backend/utils/sort/sharedtuplestore.c modified +2 −1

Discussion