[Date Prev][Date Next][Thread Prev][Thread Next]
- Subject: Re: PATCH: How to handle CallInfo func field safely?
- From: Hugo Musso Gualandi <hgualandi@...>
- Date: Wed, 21 Apr 2021 01:28:29 -0300
I analyzed the use of CallInfo func field,
then I figured out that the field is used as either CClosure or
There are actually 3 kinds of functions:
- Lua closures
- C closures
- Light C functions
The Lua calling convention is to push the function object to the Lua
stack, followed by the function arguments. The `func` field refers to
this function object, which can be any of the 3 function types.
First, at the entry of the VM dispatch loop (Lua 5.4.3),
the CallInfo func field is cast as LClosure as follows:
The VM dispatch loop only makes sense for Lua closures. It's only
called in situations where it's known that it's a Lua closure.
That said, now that you mention it really is a bit strange that it does
a straight cast with clLvalue, without any checking. I wonder if it
would make sense to have the `cl` be one of the parameters to
luaV_execute. The places that call luaV_execute are all places that
have checked the type tag of the function object and have the `cl` at
Furthermore, the function index2value (./src/lapi.c) assumes that
ci->func is type of either CClosure or LClosure implicitly as follows:
I think you might mean "light C function" instead of "Lua closure". The
C API stuff is only accessible to C functions.