Compatibility with FILE* metatype broken on LuaJIT

[jgmdev]

The following code causes an overwrite of the file metatype from FILE* to userdata which breaks compatibility with native C functions that expect a FILE* when performing something like luaL_checkudata(L, 1, LUA_FILEHANDLE);

lua-compat-5.3/compat53/module.lua

Lines 829 to 881 in dfd83b4

	if is_luajit then
	local compat_file_meta = {}
	local compat_file_meta_loaded = 0
	local function load_compat_file_meta(file_meta)
	-- fill compat_file_meta with original entries
	for k, v in pairs(file_meta) do
	compat_file_meta[k] = v
	end
	compat_file_meta.__index = {}
	for k, v in pairs(file_meta.__index) do
	compat_file_meta.__index[k] = v
	end
	compat_file_meta_loaded = 1
	-- update it with compatibility functions
	local file_mt_ok, file_mt = pcall(require, "compat53.file_mt")
	if file_mt_ok then
	file_mt.update_file_meta(compat_file_meta, is_luajit52)
	compat_file_meta_loaded = 2
	end
	end
	local function return_fd(fd, err, code)
	if not fd then
	return fd, err, code
	end
	if fd and debug_setmetatable then
	if compat_file_meta_loaded == 0 then
	local file_meta = gmt(fd)
	load_compat_file_meta(file_meta)
	end
	if compat_file_meta_loaded == 2 then
	debug_setmetatable(fd, compat_file_meta)
	end
	end
	return fd
	end
	function M.io.open(...)
	return return_fd(io_open(...))
	end
	function M.io.popen(...)
	return return_fd(io_popen(...))
	end
	function M.io.tmpfile(...)
	return return_fd(io_tmpfile(...))
	end
	end

I don't know what is the motive for this code but from my quick testing this change doesn't seems needed since the lines() and read() methods are properly overwritten from here for all subsequently created file objects:

lua-compat-5.3/compat53/init.lua

Lines 26 to 29 in dfd83b4

	if type(file_meta) == "table" and type(file_meta.__index) == "table" then
	local file_mt = require("compat53.file_mt")
	file_mt.update_file_meta(file_meta, is_luajit52)
	end -- got a valid metatable for file objects

For reference: pragtical/pragtical#228