the foreign c-string type: what animal is that?

Hi,

c-string is a dangerous area. Witness this comment in a project where I participated, using CMUCL:

;; when I reported the :in-out c-string GC bug (1996), CMU thought it was
;; dangerous anyway and disabled :in-out c-string combination.
;; We work around the problem by not using DEF-ALIEN-ROUTINE and call
;; the function directly.
 ... (alien-funcall (extern-alien #) #)

I'm looking for advice on this topic. I really have a problem with foreign/alien c-string types.

(malloc 'c-string "abc") does in fact two allocations:
1. one for the pointer, since char* IS a pointer
2. one for the buffer contents

This problem does not arise when allocating buffers directly:
(malloc '(c-array character 13) "abcde...")
like (malloc 'int -123456789)

This is a fundamental difference!

Any ideas greatly appreciated.

I had the following idea. A malloc with initialization doesn't allocate a c-string (pointer object) and a buffer. Instead, it creates a foreign-variable of type (:array character <N>) where <N> is computed dynamically as (1+ (length init)). But I don't like exceptions to otherwise regular schemes. And it cannot handle malloc without initarg.

Commens are highly appreciated,
	Jorg Hohle.