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expression_tree_walker and allied functions have traditionally declared their callback functions as, say, "bool (*walker) ()" to allow for variation in the declared types of the callback functions' context argument. This is apparently going to be forbidden by the next version of the C standard, and the latest version of clang warns about that. In any case it's always been pretty poor for error-detection purposes, so fixing it is a good thing to do. What we want to do is change the callback argument declarations to be like "bool (*walker) (Node *node, void *context)", which is correct so far as expression_tree_walker and friends are concerned, but not change the actual callback functions. Strict compliance with the C standard would require changing them to declare their arguments as "void *context" and then cast to the appropriate context struct type internally. That'd be very invasive and it would also introduce a bunch of opportunities for future bugs, since we'd no longer have any check that the correct sort of context object is passed by outside callers or internal recursion cases. Therefore, we're just going to ignore the standard's position that "void *" isn't necessarily compatible with struct pointers. No machine built in the last forty or so years actually behaves that way, so it's not worth introducing bug hazards for compatibility with long-dead hardware. Therefore, to silence these compiler warnings, introduce a layer of macro wrappers that cast the supplied function name to the official argument type. Thanks to our use of -Wcast-function-type, this will still produce a warning if the supplied function is seriously incompatible with the required signature, without going as far as the official spec restriction does. This method fixes the problem without any need for source code changes outside nodeFuncs.h/.c. However, it is an ABI break because the physically called functions now have names ending in "_impl". Hence we can only fix it this way in HEAD. In the back branches, we'll have to settle for disabling -Wdeprecated-non-prototype. Discussion: https://postgr.es/m/CA+hUKGKpHPDTv67Y+s6yiC8KH5OXeDg6a-twWo_xznKTcG0kSA@mail.gmail.com |
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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: 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/.