Re: C under Lua

[herviou <herviou@...>]

Lisa Parratt wrote:

> Ryanne Thomas Dolan wrote:
>
> > hmm...  It seems to me that this could be used to easily generate 
> > glue functions on the fly.  For example, consider a Lua function:
> >
> > wrap (f, r, [p1, p2, ..])
> >
> > which returned a glue function for C function f with parameter types 
> > p1, p2, ... and return type r.  For example, if I wanted to use 
> > OpenGL's glTranslated:
> >
> > glTranslated = wrap ("glTranslated", "void", "number", "number", 
> > "number");
> >
> > This would generate and compile something like the following in tcc:
> >
> > LUALIB_API int glue_glTranslated (lua_State *L)
> > {
> >         glTranslated (lua_tonumber (L, 1), lua_tonumber (L, 2), 
> > lua_tonumber (L, 3));
> >
> >         return 0;
> > }
> >
> > Obviously I am leaving out a lot of details such as external 
> > libraries but I think this general idea could prove very useful for 
> > exporting C libraries to Lua /without ever writing C code/.  It would 
> > not be hard to optimize it to compile the tcc code upon the first 
> > call of the function (kinda like LuaJIT).
> >
> > By the way, it seems to me that this should be possible using just 
> > gcc (though much slower of course).  It should be possible to 
> > implement such a system that falls back on gcc if tcc is not installed.
>
>
> All of this can be achieved in a much more compact manner by using a 
> compiler to extract a decorated syntax tree and by maintaining the 
> symbol table. In addition to this, all you require is a short routine 
> that prepares translates a Lua stack frame into a Native stack frame, 
> performs the call, and then converts it back.

Yep but...All depends the usage you want to have for this. If its just 
generating stub for lua, tools already exist. I think the use for such a 
compiler in the Lua context is to generate simple function with 
"classic" args (you're right for data model.) for fast prototyping 
issues (Sometimes it's a little bit "mean" to wrapp by hand one or two 
functions in C ;-). If we need more complicated wrapped functions I 
think an offline tools is better.

> The *main* issue with automatic binding generation for Lua is that 
> it's data model is wildly different from Cs. Since data massaging has 
> to be done to make things work smoothly, it's far more efficient to do 
> it on the C side. The only other option is to introduce funny 
> functions for manipulating C data, or to do some major surgery to Lua 
> to make it compatible.
Right.

dh.

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