2011/12/19 Sascha Ziemann
<ceving@gmail.com>
2011/12/14 Marc Feeley <feeley@iro.umontreal.ca>:
>
> When a Scheme string is "converted" to a C string by the C-interface, it is a newly allocated object on the C heap. In other words, the object that C is receiving is unrelated to the Scheme object managed by the Gambit garbage-collector. The C string will *not* be moved around, but it does have a reference count which allows more control over the reclaiming of that string from the C side.
So there are two strings: one on the Scheme side and one on the C
side. The one on the Scheme side probably does not have any Scheme
references any more but has one reference coming from the C side.
Isn't this a bit much overhead to keep the string on the Scheme side,
only to have a reference to the copy of the string on the C side?
You can access the Scheme string's content "raw" as well from C. The point with the conveniency wrapper into char* etc. in C, is to give you a latin1/utf8/etc. encoded character sequence rather than the internal 32bit/etc. unicode form.
And another question: if there are also references on the Scheme side
to the string which get used to modify the string: will the C side
know about the modification?
No afaik
Example:
(let ((ident "A"))
(openlog ident ...)
(syslog "a")
(set! ident "B")
(syslog "b"))
Will the output be
A: a
B: b
or
A: a
A: b