About some bugs

[Walter Bright]

bearophile wrote:
> I have studied more Linux bugs.
> 
> ----------------
> 
> An example of bug (more than 14 like this fixed in few years):
> 
> -       memset(pp, 0, sizeof(pp)); +       memset(pp, 0, sizeof(*pp));
> 
> -       memcpy((caddr_t)TstSchedTbl, (caddr_t)&vcIndex,sizeof(TstSchedTbl)); 
> +       memcpy((caddr_t)TstSchedTbl, (caddr_t)&vcIndex,
> sizeof(*TstSchedTbl));
> 
> Here the type system knows that pp is a pointer. sizeof(pp) is typically a
> word, while the correct sizeof(*pp) is often larger. A simple way to avoid
> this bug in D is to use a zerioing template function, something like
> (untested) (in GNU C there is a way to write a similar macro, I don't know
> why they don't use it, even if it's a bit less safe and much less nice
> looking):
> 
> void zeroit(T)(T* ptr) if (!IsPointer!T) { memset(ptr, 0, (*ptr).sizeof); }
> 
> Standard safer wrappers for some C functions may help low-level D coding.
> 
> If you don't want to use a zeroit() then a type system able to catch such
> bugs needs some nice annotations...

In D:
     pp[] = 0;
or:
     pp = typeof(pp).init;

etc.



> In this post I don't see any little rule worth adding to the D compiler.

Many of them are dealt with with D's scope guard, RIAA, and garbage collection 
support.