converting a relative stack index into an absolute stack index: a little someting missing in the C API?

[Benoit Germain <bgermain@...>]

Hello,

 

When I code a binding, I find myself having helper functions manipulating items on the stack whose index is provided by the caller. Often enough, this index is relative to the stack top.

It happens that I found a bug where the called function used this top-relative index after having itself pushed an item on the stack, thus causing the reference to something unexpected.

I therefore found myself in the need, for the called function, to ensure that the provided stack index is valid whenever it is used. So I coded this awesome piece of software:

 

__inline int lua_absindex( lua_State * const L, int const _idx)

{

       // positive or pseudo-index: return the index, else convert to absolute stack index

       return (_idx > 0) ? _idx : (_idx <= LUA_REGISTRYINDEX) ? _idx : (lua_gettop( L) + 1 + _idx);

}

 

Now, maybe the equivalent already exists in the current API (5.1.4), but I missed it. And in the event it is not the case, maybe this could be considered a useful addition to 5.2 (provided it properly covers all cases, of course)?

 

Best,

 

 

Benoit.