Re: Caveat with lua_pushlightuserdata(L, (void *)&key)

["Julien Cugnière" <julien.cugniere@...>]

2006/6/24, Mike Pall <mikelu-0606@mike.de>:
> static const int regkey_foo = 1;
> static const int regkey_bar = 1;
> [...]
> The problem is that the compiler/linker may decide to join
> constants with identical _values_. Unfortunately this makes the
> _addresses_ the same, too.

Wow, that's interesting.

> Solution:
> - Or use the addresses of non-const static variables.

Hmm, pushing the idea further, couldn't a smart optimizing compiler
automatically constify non-const variables that the code does not
modify ? You would then have to use volatile non-const static
variables...

Or is the compiler able to make any assumptions about constness once
you take the address of a variable and cast it to (void*) ?

Anyway, here is a simple way to ensure that your constants are unique
(assuming this legal C):

   static const void* regkey1 = &regkey1;
   static const void* regkey2 = &regkey2;

--
Julien Cugnière