4 ms·

It would be interesting to see a language that implements RAII but provides a GC as a fall-back.

• dmead 9y ago
  or just manual memory management with gc as a catchall..
• advisedwang 9y ago
  You might like to have fun with the Boehm GC: http://www.hboehm.info/gc/ http://www.hboehm.info/gc/.
• akvadrako 9y ago
  Python uses reference counting with GC as a fall-back. RAII is basically reference counting with destructors, but it's not very useful if the object lifetimes are not easy to reason about. The optional GC (for circular references) greatly complicates things. [1] http://arctrix.com/nas/python/gc/ http://arctrix.com/nas/python/gc/
• zokier 9y ago
  Rust went through that stage at one point. It had language-level support for GC, first by having @-pointers (e.g. @i32 would have been pointer to GC-managed int) and later when sigils were removed it had short-lived Gc<T> type. iirc GC support was finally completely removed during the crunch to 1.0. I'd point out that afaik rustc never got a proper good GC implementation (which probably weighted heavily in the decision to remove it before 1.0), so @T/Gc<T> were mostly plain old refcounted pointers with some smoke and mirrors. See http://words.steveklabnik.com/pointers-in-rust-a-guide http://words.steveklabnik.com/pointers-in-rust-a-guide for example (section "Managed pointers")
• kazinator 9y ago
  TXR Lisp supports a form of RAII: This is the TXR Lisp interactive listener of TXR 181. Quit with :quit or Ctrl-D on empty line. Ctrl-X ? for cheatsheet. 1> (defstruct raii-class nil (:init (me) (put-line "raii-class hello")) (:fini (me) (put-line "raii-class goodbye"))) #<struct-type raii-class> 2> (with-objects ((o (new raii-class))) (put-line "inside block")) raii-class hello inside block raii-class goodbye t Constructor abort via non-local transfer: 3> (defstruct ctor-throws nil (:init (me) (error "refuse to init")) (:fini (me) (put-line "ctor-throws goodbye"))) #<struct-type ctor-throws> 4> (new ctor-throws) ctor-throws goodbye ** refuse to init ** during evaluation at expr-3:2 of form (error "refuse to init") :fini called by GC: 5> (progn (new raii-class) nil) raii-class hello nil 6> (sys:gc) raii-class goodbye t with-objects is not just with structs but for anything with a GC finalizer, like the (1 2 3) list in this example: 6> (with-objects ((o (new raii-class)) (p [finalize (list 1 2 3) prinl])) (put-line "inside block")) raii-class hello inside block (1 2 3) raii-class goodbye t with-objects can't be used for defining function arguments, but it can refer to variables in scope; resource not defined in the block can be finalized: 11> (let ((x (new raii-class))) (with-objects ((x x)) (put-line "inside-block"))) raii-class hello inside-block raii-class goodbye t Parameter passing has reference semantics so the smart-pointer style RAII use of C++ across function interfaces is not really applicable. We don't want to copy a struct argument when a function is called and be incrementing refcounts on things the struct's slots point to; that's just stupid.