local external = {}

function system.DebugJIT(b)
    if b then
        jit.attach(function(what, tr, func, pc, otr, oex)
            if what == "abort" then
                setlogfile("jit_trace_debug")

                -- try to translate the external function to a name
                local ext_name = external[oex]

                if not ext_name then
                    -- try once if it doesn't exist, maybe it'sa module
                    for k, v in pairs(_G) do
                        if type(v) == "function" then
                            external[v] = k
                        elseif type(v) == "table" then
                            for k2, v in pairs(v) do
                                if type(v) == "function" then
                                    external[v] = k .. "." .. k2
                                end
                            end
                        end
                    end
                    ext_name = external[oex] or tostring(oex)
                end

                -- try to figure out a better name for the function that couldn't be jit compiled
                local lua_name = func
                local info = debug.getinfo(func)

                if info.source then
                    local lua = vfs.Read(info.source:sub(2))
                    if lua then
                        lua_name = lua:explode("\n")[info.linedefined]
                    end
                end

                if lua_name then
                    lua_name = lua_name:explode("\n")[1]
                    lua_name = lua_name:trim()
                else
                    lua_name = func
                end

                if not ext_name then
                    ext_name = table.concat({tostringargs(what, tr, func, pc, otr, oex)}, ", ")
                end

                logf("could not jit compile %q because of the external function %s", lua_name, ext_name)

                setlogfile()
            end
        end, "trace")
    else
        -- how to disable?
        jit.attach(function() end, "trace")
    end
end