Re: Smashing the Stack?

[Dan Kaminsky <dan () doxpara com>]

> the real question is how did the gcc developers come to this solution ?
> I mean ... it looks pretty stupid. for a 3 chars buffer the compiler 
> alocates 24 bytes and for a 4 chars buff only 4 bytes ?!?!?!
> the same problem you encounter if you go further with your exploration:
> for a 7 chars buff -> 24 bytes
> for a 8 chars buff -> 8 bytes :)))))))))))
>
> isn't it dumb ? it's been allready a pretty long time since I keep 
> looking for somebody to explain why does the gcc alocate space in this 
> manner.
>
>  
4 chars = 4 bytes = 32 bits
8 chars = 8 bytes = 64 bits

Unsurprisingly, it looks like GCC is trying to be more efficient when 
operating on variables or structures that align across 2^n (hardware 
boundries / programmer fetish).  My guess, completely pulled out of my 
ass, is that non-2^n stuff is thrown on the stack inline with all 
metadata, while 2^n stuff has all the metadata piled on in the beginning 
with pointers to actual data.  So to read a bunch of vars, you just do a 
mass copy, instead of repeatedly skipping around.

I don't do much with stacksmashing, but that's what I assume is going on.

--Dan