Question

I want to call the Lua script, which require() lyamlmodule, the Lua binding for LibYAML, from C program.

I compiled Lua 5.2 from the source, and I hacked the module so that it works with Lua 5.2. It can be found on github .

The following is a Lua script, it works either with Lua 5.1, and with 5.2:

-- foo.lua
require('lyaml')

function hello ()
  res = lyaml.load("a: 4\n")
  return res.a
end

-- then calling hello() it works like a charm
print( hello() ) -> 4

Problem

I wrote a C program that should invoke hello()from a script, following Lua Programming, chapter 25 and the Lua 5.2 Reference Manual .

Program C:

/* foo.c */
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>

int main(void)
{
  double z;

  lua_State *L = luaL_newstate();
  luaL_openlibs(L);

  if (luaL_dofile(L, "foo.lua"))
    luaL_error(L, "error running script: %s", lua_tostring(L, -1));

  lua_getglobal(L, "hello");

  if (lua_pcall(L, 0, 1, 0) != 0)
    luaL_error(L, "error calling hello: %s", lua_tostring(L, -1));

  if (!lua_isnumber(L, -1))
    luaL_error(L, "result must be number");        

  z = lua_tonumber(L, -1);
  lua_pop(L, 1);

  lua_close(L);
  return 0;
}

I am compiling the release:

gcc -Wall -o foo foo.c -ldl -lm -llua

Then when I run fooat runtime, I get the following error:

PANIC: unprotected error in call tu Lua API (
    error running script: error loading module 'lyaml' from file '/path/to/lyaml.so':
       /path/to/lyaml.so: undefined symbol: lua_gettop)
Aborted

So, I tried to load lyamlfrom program C, adding the following line after the call luaL_openlibs():

luaL_requiref(L, "lyaml", luaopen_package, 1);

:

PANIC: unprotected error in call tu Lua API (
    error running script: 
       hello.lua:4: attempt to index global 'lyaml' (a nil value))
Aborted

, , lyaml , require() .

luaL_requiref(), , modname glb true:

void luaL_requiref (lua_State *L, const char *modname, 
                    lua_CFunction openf, int glb);

openf modname package.loaded[modname], require.

glb , modname.
.

require() Lua script, .

? - ?

, () / :

lua_strlen() -> luaL_len()
luaL_reg     -> luaL_Reg
luaL_getn()  -> luaL_len()

Lua lyaml , , .

lyaml Lua 5.1. , , .

UPDATE

, , C Lua 5.1. 5.2, .

lyaml = require('lyaml')