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858fb27b69
A negative n means "return all but the first |n| characters", so
text_right() negates n before clipping. Negating PG_INT32_MIN
overflows; with -fwrapv the result is PG_INT32_MIN again, still
negative, and pg_mbcharcliplen() then returns an offset of zero,
so the whole string is returned where the correct answer is an
empty string:
SELECT right('abcdef', (-2147483648)::int4); -- 'abcdef', want ''
SELECT right('abcdef', -2147483647); -- '', correct
Clamp to PG_INT32_MAX instead. Any n whose absolute value is at
least the string's length skips all of it, and a text value cannot
be longer than PG_INT32_MAX, so this gives the same answer for every
other input. Erroring out, as text_format_string_conversion() does
for a width of INT_MIN, would not be correct here: unlike a format
width, an out-of-range skip count has a well-defined result.
Using pg_neg_s32_overflow() would be a slightly more optimal fix but
as it's only available in PostgreSQL 18 and later the decision was
taken to apply the same fix to all backbranches.
Backpatch to all supported versions.
Author: Ewan Young <kdbase.hack@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CAON2xHNnBz-AcPJgDmd5_39+8qR5AUKEZk4X3ZM-0zdsATn8kQ@mail.gmail.com
Backpatch-through: 14
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.