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Fetch the next-item pointer before the call not after, so that we aren't dereferencing a dangling pointer if the callback deregistered itself during the call. The risky coding pattern appears in CallXactCallbacks, CallSubXactCallbacks, and ResourceOwnerReleaseInternal. (There are some other places that might be at hazard if they offered deregistration functionality, but they don't.) I (tgl) considered back-patching this, but desisted because it wouldn't be very safe for extensions to rely on this working in pre-v16 branches. Hao Wu Discussion: https://postgr.es/m/CAH+9SWXTiERkmhRke+QCcc+jRH8d5fFHTxh8ZK0-Yn4BSpyaAg@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/.