5c9d17e94c
This macro cast the result to BlockNumber after shifting, not before, which is the wrong thing. Per the C spec, the uint16 fields would promote to int not unsigned int, so that (for 32-bit int) the shift potentially shifts a nonzero bit into the sign position. I doubt there are any production systems where this would actually end with the wrong answer, but it is undefined behavior per the C spec, and clang's -fsanitize=undefined option reputedly warns about it on some platforms. (I can't reproduce that right now, but the code is undeniably wrong per spec.) It's easy to fix by casting to BlockNumber (uint32) in the proper places. It's been wrong for ages, so back-patch to all supported branches. Report and patch by Zhihong Yu (cosmetic tweaking by me) Discussion: https://postgr.es/m/CALNJ-vT9r0DSsAOw9OXVJFxLENoVS_68kJ5x0p44atoYH+H4dg@mail.gmail.com
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/.