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Commitc6f7f11d8intended to prevent leaking any PyObject reference counts in edge cases (such as out-of-memory during string construction), but actually it introduced a leak in the normal case. Repeating an error-trapping operation often enough would lead to session-lifespan memory bloat. The problem is that I failed to think about the fact that PyObject_GetAttrString() increments the refcount of the returned PyObject, so that simply walking down the list of error frame objects causes all but the first one to have their refcount incremented. I experimented with several more-or-less-complex ways around that, and eventually concluded that the right fix is simply to drop the newly-obtained refcount as soon as we walk to the next frame object in PLy_traceback. This sounds unsafe, but it's perfectly okay because the caller holds a refcount on the first frame object and each frame object holds a refcount on the next one; so the current frame object can't disappear underneath us. By the same token, we can simplify the caller's cleanup back to simply dropping its refcount on the first object. Cleanup of each frame object will lead in turn to the refcount of the next one going to zero. I also added a couple of comments explaining why PLy_elog_impl() doesn't try to free the strings acquired from PLy_get_spi_error_data() or PLy_get_error_data(). That's because I got here by looking at a Coverity complaint about how those strings might get leaked. They are not leaked, but in testing that I discovered this other leak. Back-patch, asc6f7f11d8was. It's a bit nervous-making to be putting such a fix into v13, which is only a couple weeks from its final release; but I can't see that leaving a recently-introduced leak in place is a better idea. Author: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/1203918.1761184159@sss.pgh.pa.us Backpatch-through: 13
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/.