On Sat, Jun 15, 2013 at 02:15:04PM +0200, Laurent wrote: > On Sat, Jun 15, 2013 at 1:55 PM, Roman Klochkov <[email protected]> wrote: > > > What about > > > > (define-lib foo (fun _string -> _void)) > > > > (foo "Test") > > > > ? > > > > Will be the pointer from string "Test" freed? > > > > I *think* Racket will garbage collect the "Test" value when it is not used > anymore on the Racket side, but it won't know what happens on the ffi C > side (hence the "ffi/unsafe"). > So I think the lib may point to a freed value if you're not cautious. > > > > And how to make it retain, if I need to save it on the foreign side? > > > > You can probably at least simply store it in a global variable. There may > be a better way to do it though. > For example (not tested) : > #lang racket > (define dontfreethem '()) > (define (dontfreeme x) > (set! dontfreethem (cons x dontfreethem)) > x) > > (foo (dontfreeme "Test")) > > Laurent
But the garbage collector can still move the string when collecting, so protecting it from being freed isn't enough. Isn't there some way to declare an object immovable? -- hendrik > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
