lua-users home
lua-l archive

[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index] [Thread Index]

> I'm confused then. My loadString chunk is, for instance: print ("hello")
> If I enter: return ("hello") then the stack does have a string - hello on it.
> How do I call a C function and get return results if that doesn't work?

It isn't that you're not getting results, they just aren't going anywhere. :)

The chunk is itself a Lua function (thus the pcall()), so you return
values from it
like any other. Thus a return ("hello") works, but not a naked print().

> As a workaround, I see what you mean. But not being able to get return values is confusing me. It feels like I'm doing something wrong. If 'return "hello"' works, it feels like a C function that returns values should too.

It wasn't even a workaround, really. Once you go beyond simple
one-liners (e.g. two print() statements in a row), you'd end up
needing something similar, most likely. Perhaps something like this

// Before your loadstring / pcall
lua_setglobal(luaVM, "MyTable");

// Somewhere near the end of print()
lua_getglobal(luaVM, "MyTable"); // items, table

if (!lua_isnil(luaVM, -1))
  int base = -nreturns - 1;

  for (int i = 0; i < nreturns; ++i)
    lua_pushvalue(luaVM, base + i); // items, table, items[i + 1]
    lua_rawseti(luaVM, -2, i + 1); // items, table

  lua_pushinteger(luaVM, nreturns); // Save number of items (there may be nils)
  lua_setfield(luaVM, -1, "n");

lua_pop(luaVM, 1); // items

// After your pcall, non-error case:
lua_getglobal(luaVM, "MyTable); // table
lua_getfield(luaVM, -1, "n"); // table, n

for (int i = 0, n = luaL_tointeger(luaVM, -1); i < n; ++i)
  lua_rawgeti(luaVM, -2, i + 1); // table, n, item[i]

 // DO STUFF with item on top of stack

  lua_pop(luaVM, 1); // table, n

lua_pop(luaVM, 2);