f2369bc610
Commit 5dd7fc1519 added block-level memory accounting, but used int64 variable to
track the amount of allocated memory. That is incorrect, because we have Size for
exactly these purposes, but it was mostly harmless until c477f3e449 which changed
how we handle with repalloc() when downsizing the chunk. Previously we've ignored
these cases and just kept using the original chunk, but now we need to update the
accounting, and the code was doing this:
context->mem_allocated += blksize - oldblksize;
Both blksize and oldblksize are Size (so unsigned) which means the subtraction
underflows, producing a very high positive value. On 64-bit platforms (where Size
has the same size as mem_alllocated) this happens to work because the result wraps
to the right value, but on (some) 32-bit platforms this fails.
This fixes two things - it changes mem_allocated (and related variables) to Size,
and it splits the update to two separate steps, to prevent any underflows.
Discussion: https://www.postgresql.org/message-id/15151.1570163761%40sss.pgh.pa.us
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/.