Re: RES: C++ Typecast - so far newbie question

[Rici Lake <lua@...>]

On 2-Jul-07, at 4:08 PM, Patrick Donnelly wrote:

> > On 2-Jul-07, at 2:40 PM, SosCpdTerra wrote:
> >
> > > Did someone know a better way to typecast a const char * (that is 
> about
> > > lua_tostring(L, n)) into a char * then vector or c_str()? I'm 
> fighting
> > > with
> > > that...
> >
> > Strings returned by lua_tostring *must not be modified*.
> >
> > So don't cast them to char* or evil things will happen.
>
> I'm curious about the technical reasons/consequences for this. 
> Naturally lua strings are meant to be immutable. I'm betting this has 
> something to do with their hash value changing, and thus their index 
> to the global environment (or whatever table they're in) being lost 
> because the hash changes? I assume this would cause not only losing 
> your string in the table but some segmentation faults if one attempts 
> to access them? Would the garbage collector lose sight of these 
> strings, or collect it almost immediately?

Lua interns strings; there is only one instance of each string. So if 
you changed, say, "print" to "prbnt", you'd end up changing every usage 
of "print" in the lua environment, including constants in programs and 
keys in hash tables.

After that, it gets really confusing. But it won't segfault afaik.