Re: [Proposal] Load module symbols from main program

[Xavier Wang <weasley.wx@...>]

2016-03-21 3:04 GMT+08:00 Hisham <h@hisham.hm>:
> On 20 March 2016 at 06:38, Xavier Wang <weasley.wx@gmail.com> wrote:
>> 2016-03-20 9:24 GMT+08:00 Luiz Henrique de Figueiredo <lhf@tecgraf.puc-rio.br>:
>>> I'm probably missing something but doesn't package.loadlib do what you want?
>>> It'll find any symbol you ask but of course you can only use those that
>>> are lua_CFunctions.
>>>
>>
>> Sorry for my misunderstand words. I'm not want to *load* a module and
>> find a symbol as a Lua C function, I want just *find* symbol from
>> currently loaded modules!
>>
>> e.g. I have build a custom lua.exe by only build it with extra C
>> sources, say path.c, miniz.c, and boot.c. they all export luaopen_
>> functions. after that, when my script run require "path", Lua will
>> find preload "path" module, and Lua module path.lua, and C module
>> path.so/dll, after all, it finds luaopen_path in currenty host
>> program, and it finds out it. so the module is loaded.
>>
>> or, my project has severals lua script embedded into my program, I
>> just compile these into .c file:
>> #define LUA_LIB
>> #include <lua.h>
>> LUALIB_API int luaopen_<scriptname>(lua_State *L) {
>>   size_t chunksize = <chunksize>;
>>   const char *chunk = ".....";
>>   luaL_loadbuffer(....)
>> }
>>
>> you can just build this .c file into your host program, you can use
>> require to load this embedded Lua module, not need any register
>> things. because the symbol luaopen_<scriptname> is already in your
>> namespace!
>>
>> In this way, if you want debug module not loaded defaultly, just
>> remove it out of linit.c list, and you can require "debug" to load it,
>> not modify any other things.
>>
>> to load these functions, you should use GetModuleHandle(NULL) or
>> dlopen(NULL) on Windows or Linux, but we can not do this by loadlib or
>> require.
>>
>> what I want is when I compile a exe, I just add a source file that
>> export a Lua library function (luaopen_whatever), and I can require
>> it.
>
> ...without having to edit linit.c. That's the point, right?
>
> I'm afraid there's no way to do this in ANSI C (or even in POSIX,
> according to my reading of the dlfcn.h functions in `man dlopen`).
>
> You might be able to implement this yourself in a Linux-specific
> manner using the functions from link.h, but I never tried.
>
> -- Hisham
>

loadlib itself is not ANSI C, but you can do it in POSIX, see[1]:

The function dlopen() loads the dynamic library file named by the
null-terminated string filename and returns an opaque "handle" for the
dynamic library. If filename is NULL, then the returned handle is for
the main program. If filename contains a slash ("/"), then it is
interpreted as a (relative or absolute) pathname. Otherwise, the
dynamic linker searches for the library as follows (see ld.so(8) for
further details)

[1]: http://linux.die.net/man/3/dlopen

-- 
regards,
Xavier Wang.