Q:

compile lua shared object into embeded c

i have this code (zstring.c)
#include "lua.h"
#include "lualib.h"
#include "lauxlib.h"
#include <string.h>

static int zst_strlen(lua_State *L)
{
    size_t len;
    len = strlen(lua_tostring(L, 1));
    lua_pushnumber(L, len);
    return 1;
}

int luaopen_zstring(lua_State *L) 
{
    lua_register(L,"zst_strlen", zst_strlen);
    return 0;
}

and this is my lua embedded
int main (){
    L = luaL_newstate();
    luaL_openlibs(L);
    luaL_dofile(L, "test.lua");
    lua_close(L);
    return 0;
}

i do not want compile zstring.c to zstring.so object
i want zstring.c compile into my embedded lua then i can call zstring from test.lua and use it
how to do it?

A:

You can accomplish this by including the zstring source file then calling luaopen_zstring after initializing Lua:
#include "zstring.c"

int main (){
    L = luaL_newstate();
    luaL_openlibs(L);
    lua_pushcfunction(L, luaopen_zstring);
    lua_call(L, 0, 0);
    luaL_dofile(L, "test.lua");
    lua_close(L);
    return 0;
}

It should be noted that even if you do not want to generate a shared library, you can still create an object file for zstring (by using the -c flag with gcc, for example). You can then link that object file with your main source. 
The steps for doing this are roughly:

Compile zstring.c to an object file (e.g. gcc -c -o zstring.o zstring.c)
Create a header file named zstring.h:
#ifndef ZSTRING_H
#define ZSTRING_H
int luaopen_zstring(lua_State *L);
#endif

Include the header in your main source file: 
#include "zstring.h"

int main (){
    L = luaL_newstate();
    luaL_openlibs(L);
    lua_pushcfunction(L, luaopen_zstring);
    lua_call(L, 0, 0);
    luaL_dofile(L, "test.lua");
    lua_close(L);
    return 0;
}

Compile the main file with the zstring.o object file linked (e.g. gcc -o myprogram main.c zstring.o)

