Re: [Chicken-hackers] CHICKEN in production

[John Cowan]

Peter Bex scripsit:

> It was discussed before on this list, and I shot it down due to
> the danger, however I think it may be possible to change the string
> representation to always include a \0 at the end, so that passing it
> to C will simply be a matter of passing a pointer.

+1 to that.

> The danger could be avoided by a taint bit: if the string is known
> to not contain \0, it can be passed directly.  Otherwise, it needs to
> be checked and marked if it's safe.  If it's unsafe, an exception can
> be thrown.

IMO the better approach is simply to forbid NUL in strings altogether.
It has no semantics as a character: there is never any situation in which
you need the NUL character as opposed to the 0 byte in a bytevector.
The R7RS was worded to allow implementations to do this.

> The upshot of this is that a string will need to be checked at most
> once, and never copied (except as is done normally, by the GC).

Well, string-set! and string-fill! and the like would have to check
for inserting NUL and either set the taint bit (if you really want
to keep such strings available) or barf.

-- 
John Cowan          http://www.ccil.org/~cowan        address@hidden
If [Tim Berners-Lee] has seen farther than others,
        it is because he is standing on a stack of dwarves.  --Mike Champion