lua5.2's error: multiple Lua VMs detected - lua

Question

I use 5.2 for learning recently, what I want to try like this:
Step 1, build a c module for lua:
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
#include <stdlib.h>
static int add(lua_State *L) {
int x = luaL_checkint(L, -2);
int y = luaL_checkint(L, -1);
lua_pushinteger(L, x + y);
return 1;
}
static const struct luaL_Reg reg_lib[] = {
{"add", add}
};
int luaopen_tool(lua_State *L) {
luaL_newlib(L, reg_lib);
lua_setglobal(L, "tool");
return 0;
}
I compile and link it with liblua.a, and I'm sure it works well in lua script like "require("tool") tool.add(1, 2)"
Step 2, I write another C program that wants to require my c module in step 1 like this:
#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
#include <stdlib.h>
int main(int argc, char* const argv[]) {
lua_State *L = luaL_newstate();
luaL_requiref(L, "base", luaopen_base, 1);
luaL_requiref(L, "package", luaopen_package, 1);
lua_getglobal(L, "require");
if (!lua_isfunction(L, -1)) {
printf("require not found\n");
return 2;
}
lua_pushstring(L, "tool");
if (lua_pcall(L, 1, 1, 0) != LUA_OK) {
printf("require_fail=%s\n", lua_tostring(L, -1));
return 3;
}
lua_getfield(L, -1, "add");
lua_pushinteger(L, 2);
lua_pushinteger(L, 3);
lua_pcall(L, 2, 1, 0);
int n = luaL_checkint(L, -1);
printf("n=%d\n", n);
return 0;
}
I also compile & link with liblua.a, but error occurs when I run it:
"require_fail=multiple Lua VMs detected"
Someone's blog said that in lua5.2, you should link c module and c host program both dynamicly, but not staticly.
is there someone that has the same problem, or is there somehing wrong in my code, thanks.
NOTICE:
the problem has been solved by compile main program with -Wl,-E, thanks a lot for all your help ^^.

Answer 1

Don't link your C module with liblua.a when you create a .so from it. For examples, see my page of Lua libraries: http://www.tecgraf.puc-rio.br/~lhf/ftp/lua/ . You can link liblua.a statically into your main program but you have to export its symbols by adding -Wl,-E at link time. That's how the Lua interpreter is built in Linux.