Function call_lua

example/lua_callback_exceptions.cpp:111–146

If do_work succeeds, we return the resulting int answer. If it fails, we'll communicate that failure to our caller.

// If do_work succeeds, we return the resulting int answer. If it fails, we'll
// communicate that failure to our caller.
int call_lua( lua_State * L )
{
    return leaf::try_catch(
        [&]
        {
            leaf::error_monitor cur_err;

            // Ask the Lua interpreter to call the global Lua function call_do_work.
            lua_getfield( L, LUA_GLOBALSINDEX, "call_do_work" );
            if( int err = lua_pcall(L, 0, 1, 0) )
            {
                std::string msg = lua_tostring(L, 1);
                lua_pop(L,1);

                // We got a Lua error which may be the error we're reporting
                // from do_work, or some other error. If it is another error,
                // cur_err.assigned_error_id() will return a new leaf::error_id,
                // otherwise we'll be working with the original error reported
                // by a C++ exception out of do_work.
                leaf::throw_exception( cur_err.assigned_error_id().load( e_lua_pcall_error{err}, e_lua_error_message{std::move(msg)} ) );
            }
            else
            {
                // Success! Just return the int answer.
                int answer = lua_tonumber(L, -1);
                lua_pop(L, 1);
                return answer;
            }
        },

        []( e_lua_exception e ) -> int
        {
            // This is the exception communicated out of wrap_lua_CFunction.
            std::rethrow_exception( e.value );
        } );
}

int main()
{