Re: Replaced print function return stack getting emptied
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- Subject: Re: Replaced print function return stack getting emptied
- From: Steven Johnson <steve@...>
- Date: Sun, 6 May 2012 15:37:33 -0500
> 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
(UNTESTED!):
// Before your loadstring / pcall
lua_newtable(luaVM);
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);