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c6e0fe1f2 added a new pointer field to SlabBlock to make it 4 bytes larger on 32-bit machines. Prior to that commit, the size of that struct was a multiple of 8, which meant that MAXALIGN(sizeof(SlabBlock)) was the same as sizeof(SlabBlock), however, after c6e0fe1f2, due to the addition of the new pointer field to store a pointer to the owning context, that was no longer true on builds with sizeof(void *) == 4. This problem was highlighted by an Assert failure which was checking that the pointer given to pfree() was MAXALIGNED. Various 32-bit ARM buildfarm animals were failing. These have MAXIMUM_ALIGNOF of 8. The only 32-bit testing I'd managed to do on c6e0fe1f2 had been on x86, which has a MAXIMUM_ALIGNOF of 4, therefore did not exhibit this issue. Here we define Slab_BLOCKHDRSZ and copy what is being done in aset.c and generation.c for doing calculations based on the size of the context's block type. This means that SlabAlloc() will now always return a MAXALIGNed pointer. This also fixes an incorrect sentinel_ok() check in SlabCheck() which was incorrectly checking the wrong sentinel byte. This must have previously not caused any issues due to the fullChunkSize never being large enough to store the sentinel byte. Diagnosed-by: Tomas Vondra, Tom Lane Author: Tomas Vondra, David Rowley Discussion: https://postgr.es/m/CAA4eK1%2B1JyW5TiL%3DyV-3Uq1CrfnTyn0Xrk5uArt31Z%3D8rgPhXQ%40mail.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/.