Previously this was mixed with vcruntime, with some objects being shared. But this is messy. Instead use a separate library and link ucrtbase to this as well. This also matches more closely how native libraries are organized, where vcstartup is merged into the CRT import libraries, while vcruntime is merged into the static CRT libraries.
Note: On Windows, where a long double is the same as a double, nextafterl is the same as nextafter, nexttowardl is the same as nexttoward.
Also nexttoward is the same as nextafter.
Windows ships ucrtbase without debug exports and ucrtbased with debug exports. The wine test tests ucrtbase and loads it dynamically in some cases. Compiling it with _DEBUG requires it to be linked to ucrtbased, which causes problems, because it also dynamically loads ucrtbase, which will cause it to crash.
Some old names redirect to functions that are not exported by ucrtbase. Place them into a seperate asm file, so that they don't get pulled in, when any of the other ones is referenced.
Previously sprintf and _vsnprintf were imported from ntdll. These functions are defined as inline functions in ucrt headers, but linked directly by legacy CRT code.
vcruntime contains the code that is linked into ucrtbase (in VS it is also provided as vcruntime140.dll)
vcstartup contains the code that is statically linked into executables that link to ucrtbase.dll. In Visual Studio this is part of msvcrt.lib (the import library for msvcrt), similar to our current msvcrtex, and it gets linked when you link to ucrtbase as well. The name is based on the folder name in the library.
Both libraries share some code, but each file is only compiled once.
Timo Kreuzer