Re: Adding module+DLL to Lua for Windows (LfW)

[Joshua Jensen <jjensen@...>]

----- Original Message -----
From: steve donovan
Date: 12/9/2009 5:02 AM
> On another note, the Windows .dll model is irritating because an
> extension must be compiled to link against a specific .dll, unlike
> with Unix where the extension finds its dependencies dynamically from
> its link context.  This makes it trivial to have both luajit and lua
> executables together on Linux, but this would be a bitch to get right
> on Windows.
>    
What I would like to see (and experimented with once) is for Lua to load 
the Lua module and call the luaopen_ function by passing in a structure 
of pointers to all the exported Lua functions.

struct lua_Exports
{
    ...
    void  (*lua_pushvalue) (lua_State *L, int idx);
};

int luaopen_mymodule(lua_State *L, lua_Exports *exports);

A helper function called by luaopen_mymodule could be made available to 
expand that structure into global variables:

/* lua_exportglobals.h */
void (*lua_pushvalue)(lua_State *L, int idx);

void lua_copyexportstoglobals(lua_Exports *exports)
{
    lua_pushvalue = exports->lua_pushvalue;
}

Then all other Lua use is the same.

There are important benefits to this approach.  The Lua module would 
never need to link against the Lua DLL.  An embedded static Lua 
distribution in an executable could load any Lua module as easily as 
lua5.1.dll; this can't happen right now as the Lua module .dll/.so 
embeds the Lua DLL name.  Worse, on Mac OS X, the full path to the Lua 
shared library is embedded in the module.  The shared library MUST be at 
that location.  To run a Lua distribution local to my application, I 
have to recompile everything and use @executable_path (which isn't 
always convenient).

Thoughts?

Josh