A new warning in MSVC 19.44.35207.1 (Visual Studio 17.14, released May 13, 2025) breaks the Fossil build from current trunk:

...\extsrc\shell.c(25640): error C2220: the following warning is treated as an error
...\extsrc\shell.c(25640): warning C5287: operands are different enum types 'HelpWanted' and 'HelpHave'; use an explicit cast to silence this warning
...\extsrc\shell.c(25640): note: to simplify migration, consider the temporary use of /Wv:18 flag with the version of the compiler with which you used to build without warnings

The build succeeds with the suggested /Wv:18 option added to CFLAGS, but this is probably not backwards compatible.