The 64-bit Windows ABI defines a generalized exception handling mechanism, which I believe is shared across C++ exceptions and structured exceptions available even in other languages such as C.
If I'm writing an x86-64 assembly routine to be compiled in nasm and linked into a C or C++ library, what accommodations do I need make on Windows in terms of generating unwind info and so on?
I'm not planning on generating any exceptions directly in the assembly code, although I suppose it is possible that the code may get an access violation if a user-supplied buffer is invalid, etc.
I'd like the write the minimum possible to get this to work, especially since it seems that nasm has poor support for generating unwind info and using MASM is not an option for this cross-platform project. I do need to use (hence save and restore) non-volatile registers.
As a general rule, Windows x64 requires all functions to provide unwind information. The only exception is for leaf functions which do not modify rsp and do not modify any nonvolatile registers.