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Because not every path through JsonbIteratorNext() sets val->type, some compilers complain that compareJsonbContainers() is comparing possibly-uninitialized values. The paths that don't set it return WJB_DONE, WJB_END_ARRAY, or WJB_END_OBJECT, so it's clear by manual inspection that the "(ra == rb)" code path is safe, and indeed we aren't seeing warnings about that. But the (ra != rb) case is much less obviously safe. In Assert-enabled builds it seems that the asserts rejecting WJB_END_ARRAY and WJB_END_OBJECT persuade gcc 15.x not to warn, which makes little sense because it's impossible to believe that the compiler can prove of its own accord that ra/rb aren't WJB_DONE here. (In fact they never will be, so the code isn't wrong, but why is there no warning?) Without Asserts, the appearance of warnings is quite unsurprising. We discussed fixing this by converting those two Asserts into pg_assume, but that seems not very satisfactory when it's so unclear why the compiler is or isn't warning: the warning could easily reappear with some other compiler version. Let's fix it in a less magical, more future-proof way by changing JsonbIteratorNext() so that it always does set val->type. The cost of that should be pretty negligible, and it makes the function's API spec less squishy. Reported-by: Erik Rijkers <er@xs4all.nl> Author: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/988bf1bc-3f1f-99f3-bf98-222f1cd9dc5e@xs4all.nl Discussion: https://postgr.es/m/0c623e8a204187b87b4736792398eaf1@postgrespro.ru 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/.