They don't per se need to renumber system calls, but for the most part the NT kernel developers saw little reason to enforce syscall number stability. Use of D

They don't per se need to renumber system calls, but for the most part the NT kernel developers saw little reason to enforce syscall number stability. Use of DLLs is baked VERY deeply into windows. The kernel is not even a monolithic file. It is an exe like most others pulling in dlls that implement other functionality. It even features like API-set DLL redirections which mean the bootloader for the kernel needs to implement a fair bit of the PE loader functionality of the kernel just to load the kernel. (I've no real clue if there is shared code between the two loaders, or if they are two separate loaders that implement similar things. Many of the options/features of the full kernel executable loader are not really needed in the bootloader.) So it is not much of a surprise that making the numbers stable to support fully statically linked executables was not really something they cared about. From their perspective you could always just pull in the ntdll.dll for your syscalls like they intended (or more likely a higher level win32 dll that uses the syscall).