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A majority of callers seem to have believed that this was the API spec already, because they omitted any check for a NULL result, and hence would crash on an out-of-shared-memory failure. The original proposal was to just add such error checks everywhere, but that does nothing to prevent similar omissions in future. Instead, let's make ShmemAlloc() throw the error (so we can remove the caller-side checks that do exist), and introduce a new function ShmemAllocNoError() that has the previous behavior of returning NULL, for the small number of callers that need that and are prepared to do the right thing. This also lets us remove the rather wishy-washy behavior of printing a WARNING for out-of-shmem, which never made much sense: either the caller has a strategy for dealing with that, or it doesn't. It's not ShmemAlloc's business to decide whether a warning is appropriate. The v10 release notes will need to call this out as a significant source-code change. It's likely that it will be a bug fix for extension callers too, but if not, they'll need to change to using ShmemAllocNoError(). This is nominally a bug fix, but the odds that it's fixing any live bug are actually rather small, because in general the requests being made by the unchecked callers were already accounted for in determining the overall shmem size, so really they ought not fail. Between that and the possible impact on extensions, no back-patch. Discussion: <24843.1472563085@sss.pgh.pa.us> |
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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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.