[Swig-user] Swig Lua first time use issues

[Joseph T. <to...@gm...>]

Hello,
   I am trying to use SWIG to generate Lua bindings for a minimal test
case C++ program, so I can learn to use it with larger projects. I
want to learn how to call a Lua script from C/C++ and in turn I want
that Lua script to be able to call C/C++ functions.
   In my project I have created two files, test.h and test.cpp, and I
am compiling Lua 5.1 as if it were C++ (I wanted to reduce extern
statements while I learn) and statically linking against it. I have a
simple header with some basic swig commands in it. I know that
normally I would want to generate a header myself for the SWIG output,
or use a number of "extern" statements to declare the functions I
wanted to access, but for this simple test I wanted access to
everything (until I figure out what I need) so I included the swig
output as "luabinding.h".
   I can currently call Lua core functions, like print, but I cannot
load my module with require or call PrintHello. I think the module
should already be loaded because it is all statically linked, and I
was of the understanding that something in Lua or SWIG tracked that. I
have also stepped through the code enough to know that PrintHello is
being passed to Lua by the SWIG output as a CClosure, but I am not
sure how correct it is.

Any advice would be appreciated.

Here are the files and commands I used:

I ran swig on my Ubuntu machine as follows
----------
$swig2.0 -c++ -v -lua -importall -o luabinding.h test.h
----------


test.h
----------
#ifdef SWIG
    %{
        #include "test.h"
    %}
    %include stl.i
    %module testscripting
#endif

void PrintHello();
int PrintErrorMessageOrNothing(int ErrorCode);
----------


test.cpp
----------
#include "test.h"

#include "lua.h"            // Lua Core
#include "lualib.h"         // for opening the base state
#include "lauxlib.h"        // Extra Lua Goodies like lua_open()

#include "luabinding.h"
#include <iostream>

int main (int argc, char** argv)
{
    std::cout << "This program will attempt to call a lua script that
in turn runs a c function. This was output via cout streaming in C++."
<< std::endl;

    lua_State *State;           // create a pointer to Track the Lua State
    State = luaL_newstate();    // Create a Lua State
    luaopen_testscripting(State);
    luaL_openlibs(State);

    int Error = luaL_dostring(State,"print \"Hello from Lua\"");    //
run a very simple Lua script.
    PrintErrorMessageOrNothing(Error);

    //Error = luaL_dostring(State,"require \"testscripting\"");    //
does work when unremarked
    Error = luaL_dostring(State,"PrintHello");    // doesnt work either
    PrintErrorMessageOrNothing(Error);

    Error = luaL_dostring(State,"print \"Hello from Lua\"");
    PrintErrorMessageOrNothing(Error);

    lua_close(State);           // Close the Lua state

    return 0;
}

int PrintErrorMessageOrNothing(int ErrorCode)
{
    switch(ErrorCode)
    {
        case 0: // Fine
            break;
        case LUA_YIELD:
            std::cout << std::endl << "Lua Error Code(LUA_YIELD): " <<
ErrorCode << std::endl;
            break;
        case LUA_ERRRUN:
            std::cout << std::endl << "Lua Error Code(LUA_ERRRUN): "
<< ErrorCode << std::endl;
            break;
        case LUA_ERRSYNTAX:
            std::cout << std::endl << "Lua Error Code(LUA_ERRSYNTAX):
" << ErrorCode << std::endl;
            break;
        case LUA_ERRERR:
            std::cout << std::endl << "Lua Error Code(LUA_ERRERR): "
<< ErrorCode << std::endl;
            break;
        default:
            std::cout << std::endl << "Lua Error Code(Unknown Error):
" << ErrorCode << std::endl;
    }
    return ErrorCode;
}

void PrintHello()
{
    std::cout << "Hello world! From PrintHello()" << std::endl;
}
----------


Output From my program Currently
----------
This program will attempt to call a lua script that in turn runs a c
function. This was output via cout streaming in C++.
Hello from Lua

Lua Error Code(LUA_YIELD): 1
Hello from Lua
---------



-- 
- Joe Toppi
(402) 714-7539
To...@gm...