So, to make string, that is freed by reciever, I should make something like
(define _string/transfer (make-ctype _bytes (λ (v) (define b (if (string? v) (string->bytes/utf-8 v) v)) (define length (bytes-length b)) (define res (malloc 'raw length)) (memcpy res b length)) (λ (v) (register-finalizer v free)))) Or finalizer will not work (because v is _pointer, but the type returns _bytes), and instead I have to make (λ (v) (define res (cast v _pointer _bytes)) (register-finalizer v free)) ? Суббота, 25 января 2014, 14:37 -05:00 от Ryan Culpepper <ry...@ccs.neu.edu>: >On 01/25/2014 01:28 PM, Roman Klochkov wrote: >> Is making bytestring from pointer adds the pointer to GC? >> >> >> > (define x (malloc 'raw 10)) >> > x >> #<cpointer> >> > (define b (make-sized-byte-string x 10)) >> > (cpointer-gcable? b) >> #t >> > (cpointer-gcable? x) >> #f >> > (cast x _pointer _int32) >> 173726656 >> > (cast b _pointer _int32) >> 173726656 >> >> So b and x points to the same block of 10 bytes, but value of b is >> GCable and value of x is not. >> I assume, that when b will be changed, then the bytestring will be >> collected and accessing x will give segfault. Am I right? > >I think it's a bug that (cpointer-gcable? b) returns true, since the FFI >generally treats bytestrings as pointers to the memory that stores their >contents, and in this case that memory is not managed by the GC. > >The bytestring object itself (which consists of a header, a pointer, and >a length, IIRC) is collectible, but then so is the cpointer object >(which consists of a header, a pointer, and some other stuff, like a tag >list). > >So no, you should not expect a segfault. On the other hand, if you free >x and use b afterwards, then you should expect a segfault or some other >form of memory corruption. > >Ryan > -- Roman Klochkov
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