Why use LuaJIT over plain Lua here? I can't imagine that you need the extra speed in a text editor. The ffi is available for normal lua too: https://github.com/facebook/luaffifb/
So here's something to pop up a message box on Windows:
local ffi = require("ffi")
ffi.cdef[[
int MessageBoxA(void *w, const char *txt, const char *cap, int type);
]]
ffi.C.MessageBoxA(nil, "Hello world!", "Test", 0)
Compare this with the effort required to bind that function using the classic Lua/C API: create an extra C file, add a C function that retrieves and checks the argument types passed from Lua and calls the actual C function, add a list of module functions and their names, add a luaopen_* function and register all module functions, compile and link it into a shared library (DLL), move it to the proper path, add Lua code that loads the module aaaand ... finally call the binding function. Phew!
I think the main argument against Lua + luaffifb is that it might require an external dependency: luarocks. Whereas if someone were to theoretically provide Lua integration with emacs, it might be a good idea to offer the ffi library as a baseline feature.
This is a weak argument, because it should be possible to embed luaffifb plus Lua inside of a linked library, with no need to depend on luarocks.
It's probably best to explore both options.
On the down side, TCC doesn't support all the architectures I use, so I mostly use it for proof-of-concept and throw away code.
One thing I keep thinking is to possibly use TCC (or parts of it) to parse C header files directly, so it would be easier to use an FFI in Lua.
[1] https://github.com/spc476/lua-conmanorg/blob/master/src/tcc....
[2] https://github.com/spc476/lua-conmanorg/blob/master/lua/cc.l...
[3] https://github.com/spc476/LPeg-Parsers/blob/json-1.0.0/json....
My mouth was hanging open when I discovered that you could literally a verbatim header with packed structs and use it and it would work. Then I looked at the source to find out what they were using as a compiler frontend; it's all hand written. Incredible.