Re: Strange behaviour of custom lua_gettop

[Roberto Ierusalimschy <roberto@...>]

> On Fri, Jul 12, 2013 at 5:05 PM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> > 2013/7/12 lua 4web <lua4web@gmail.com>:
> >
> >> This is strange considering my_gettop is a copy of lua_gettop.
> >> I have noticed a pattern in seemingly random numbers produced by
> >> my_gettop(i.e. 1431655765 = 0x55555555), but I have no idea why it
> >> produces them instead of correct results.
> >>
> >> I'm sure I've made a simple mistake somewhere, can anybody help me find it?
> >
> > Your code works on the current version 5.2.2 on my system.
> >
> 
> I suspect that within the Lua core, TValue is defined to be an 8-byte
> NaN packed value, whereas in your test.c, TValue is defined to be a
> 16-byte structure.
> 
> In a 64-bit environment, TValue is a 16-byte structure within the Lua
> core, so the code will only break in a 32-bit environment.

You have to define LUA_CORE in any file that uses Lua internals. (Some
#defines in luaconf.h only work inside Lua core.)

-- Roberto