The problem with tolua++ and DLLs (solved!)

Today I was going to make a tiny DLL that binds some C code with tolua++, and I ran into this error message:

lua: error loading module ‘foo’ from file ‘daisydebugfoo.dll’:

        The specified procedure could not be found.

That looks like my DLL isn’t exporting the luaopen_foo function correctly. That is the function lua calls to initialize the package it just opened, and tolua++ was not declaring it properly:

TOLUA_API int luaopen_foo (lua_State* tolua_S) {
  return tolua_foo_open(tolua_S);

TOLUA_APIis defined toextern, which doesn’t mean that it will be exported by the DLL, because on windows, the magic incantation for that is__declspec(dllexport). The tolua++ header has no special treatment for Windows, so I’m guessing that problem has just never come up for them.

Once the problem is understood, the solution is easy: I added another function to dllmain.cpp that has the correct export declaration and calls the generated one.

extern "C" {
  int tolua_bar_open(lua_State*);
  int __declspec(dllexport) luaopen_foo (lua_State* L) {
    return tolua_bar_open(L);

There’s one caveat, because tolua++ has already created a function named luaopen_foo, so I had to tell it to name things differently, for which there is a command-line argument:

tolua++ -n bar foo.pkg > foo.c


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s