[gambit-list] How to pass a Scheme string to a const char*?

Sascha Ziemann ceving at gmail.com
Mon Dec 19 12:30:29 EST 2011

2011/12/14 Marc Feeley <feeley at 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?

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?


(let ((ident "A"))
  (openlog ident ...)
  (syslog "a")
  (set! ident "B")
  (syslog "b"))

Will the output be

A: a
B: b


A: a
A: b


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