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0 pointspjmlp9y ago0 comments

> Doesn't that effectively amount to manual memory management?

Not really, example in Active Oberon:

    TYPE
      point = RECORD x, y : INTEGER; END;

    VAR
      staticPoint : point; (* On the stack or global *)
      gcPoint     : POINTER TO point; (* GC pointer *)
      noGCPoint   : POINTER(UNTRACED) TO point; (* pointer not traced by the GC *)

> What particular languages are you referring to?

Mesa/Cedar, Oberon, Oberon-2, Active Oberon, Component Pascal, Modula-2+, Modula-3, D, Oberon-07, Eiffel, BETA.

There are probably a few other ones.

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fauigerzigerk9y ago

>noGCPoint : POINTER(UNTRACED) TO point;

That's fine for one point. How about N points where N varies at runtime?

If I allocate memory dynamically outside the GC's remit, I'm going to have to release that memory somehow.

pjmlpOP9y ago

Depends on the specifics of the language.

On Active Oberon's case, those pointers are still safe. They can only point to valid memory regions, think of them as weak pointers that can also point to data on the stack or global memory.

This in safe code.

If the package imports SYSTEM, it becomes an unsafe package, and then just like e.g. Rust's unsafe, the rules are bended a bit and usage with SYSTEM.NEW() SYSTEM.DISPOSE() is allowed.

Just like any safe systems programming language, it is up to the programmer to ensure this pointer doesn't escape the unsafe package.

fauigerzigerk9y ago

I still don't get how you can say that this memory is not under the GC's control but it's "not really" manual memory management either. Is it reference counting then? How does that memory get released?

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0 pointspjmlp9y ago0 comments

> Doesn't that effectively amount to manual memory management?

Not really, example in Active Oberon:

    TYPE
      point = RECORD x, y : INTEGER; END;

    VAR
      staticPoint : point; (* On the stack or global *)
      gcPoint     : POINTER TO point; (* GC pointer *)
      noGCPoint   : POINTER(UNTRACED) TO point; (* pointer not traced by the GC *)

> What particular languages are you referring to?

Mesa/Cedar, Oberon, Oberon-2, Active Oberon, Component Pascal, Modula-2+, Modula-3, D, Oberon-07, Eiffel, BETA.

There are probably a few other ones.

0 comments

fauigerzigerk9y ago

>noGCPoint : POINTER(UNTRACED) TO point;

That's fine for one point. How about N points where N varies at runtime?

If I allocate memory dynamically outside the GC's remit, I'm going to have to release that memory somehow.

pjmlpOP9y ago

Depends on the specifics of the language.

On Active Oberon's case, those pointers are still safe. They can only point to valid memory regions, think of them as weak pointers that can also point to data on the stack or global memory.

This in safe code.

If the package imports SYSTEM, it becomes an unsafe package, and then just like e.g. Rust's unsafe, the rules are bended a bit and usage with SYSTEM.NEW() SYSTEM.DISPOSE() is allowed.

Just like any safe systems programming language, it is up to the programmer to ensure this pointer doesn't escape the unsafe package.

fauigerzigerk9y ago

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