builtin: Fix `print` crashing on nil "holes".

The engine implementation of `print` packs the varargs into a
table and passes the table directly to `table.concat`. If you
pass any value not supported by `table.concat` (particularly
`nil`), the server crashes. This is unexpected behavior, as
`print` is supposed to be able to work with anything.

This patch changes the implementation so it first converts
all arguments using `tostring`, which fixes the issue and
makes the custom `print` function compatible with the stock
Lua behavior.

diff --git a/builtin/init.lua b/builtin/init.lua
index b3004468e5efd5ce853d6f942181ba5ccd9d516c..6b27cf76e16d99694165da80d2a3eddb4f4c68ff 100644 (file)
--- a/builtin/init.lua
+++ b/builtin/init.lua
@@ -12,7 +12,11 @@ if core.print then
        -- Override native print and use
        -- terminal if that's turned on
        function print(...)
-               core_print(table.concat({...}, "\t"))
+               local n, t = select("#", ...), { ... }
+               for i = 1, n do
+                       t[i] = tostring(t[i])
+               end
+               core_print(table.concat(t, "\t"))
        end
        core.print = nil -- don't pollute our namespace
 end