[Chicken-hackers] Only specialize string-length if type is definitely known

[Christian Kellermann]

Hi Hackers,

as Mario pointed out the previously commited fix for #855 was only the
sympthom not the cause of the troubles. The real cause has been the
unconditionally specialization of string-length to ##sys#size which
will segfault if given immediate types (since it is only a wrapper for
C_block_size).

So the attached patch removes #:enforce from its types.db entry.

You can test it for yourself with the following example code:

(define (t l)
  (let ((s1 (car l)))
    (zero? (string-length s1))))

(t '(1))

I am not fully sure whether I have understood the purpose of #:enforce
correctly. As I understood it signals the compiler to carry on even if
it does not know for sure which type it is, as the specialization code
will handle type errors by itself. Is that correct? Who can enlighten
me?

Cheers,

Christian

--
9 out of 10 voices in my head say, that I am crazy,
one is humming.

0001-Only-specialize-string-length-if-type-is-definitely-.patch
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