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It had always been intended that this already works correctly as pg_unreachable() uses __assume(0) on MSVC, and that directs the compiler in a way so it knows that a given function won't return. However, with ereport_domain(), it didn't work... It's now understood that the failure to determine that elog(ERROR) does not return comes from the inability of the MSVC compiler to detect the "const int elevel_" is the same as the "elevel" macro parameter. MSVC seems to be unable to make the "if (elevel_ >= ERROR) branch constantly-true when the macro is used with any elevel >= ERROR, therefore the pg_unreachable() is seen to only be present in a *conditional* branch rather than present *unconditionally*. While there seems to be no way to force the compiler into knowing that elevel_ is equal to elevel within the ereport_domain() macro, there is a way in C11 to determine if the elevel parameter is a compile-time constant or not. This is done via some hackery using the _Generic() intrinsic function, which gives us functionality similar to GCC's __builtin_constant_p(), albeit only for integers. Here we define pg_builtin_integer_constant_p() for this purpose. Callers can check for availability via HAVE_PG_BUILTIN_INTEGER_CONSTANT_P. ereport_domain() has been adjusted to use pg_builtin_integer_constant_p() instead of __builtin_constant_p(). It's not quite clear at this stage if this now allows us to forego doing the likes of "return NULL; /* keep compiler quiet */" as there may be other compilers in use that have similar struggles. It's just a matter of time before someone commits a function that does not "return" a value after an elog(ERROR). Let's make time and lack of complaints about said commit be the judge of if we need to continue the "/* keep compiler quiet */" palaver. Author: David Rowley <drowleyml@gmail.com> Reviewed-by: Peter Eisentraut <peter@eisentraut.org> Discussion: https://postgr.es/m/CAApHDvom02B_XNVSkvxznVUyZbjGAR+5myA89ZcbEd3=PA9UcA@mail.gmail.com
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.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.