CODEWITHSUNDEEP
memorycompiler-constructiongarbage-collection
Raouf
Raouf

Reputation: 58

Can a garbage collected language compile to a non-garbage collected one without including a garbage collector in the runtime?

As I understand it, when a managed language (like Haxe) can and wants to compiles to a non-managed language (like C++), it includes some form of garbage collector in the runtime.

I was wondering if it would be possible to completely abstract away memory management in the intermediate representation / abstract syntax tree, so that a garbage collector would not be needed and the default behavior (stack allocations live until end of scope and heap allocations live until freed) could be used?

Thank you!

Upvotes: 2

Views: 471

Answers (1)

sepp2k
sepp2k

Reputation: 370162

If I understood you correctly, you're asking whether it's possible to take a garbage collected language and compile it to an equivalent program in a non-garbage collected language without introducing memory errors or leaks, just by adding frees in the right places (i.e. no reference counting or otherwise keeping track of references or implementing a garbage collection algorithm in anyway or doing anything else at run time that could be considered garbage collection).

No, that is not possible. To do something like this, you'd have to be able to statically answer the question "What's the point in the program, after which a given object is no longer referenced", which is a non-trivial semantic property and thus undecidable per Rice's theorem.

You could define a sufficiently restricted subset of the language (something like "only one live variable may hold a strong reference to an object at a time and anything else must use weak references"), but programming in that subset would be so different from programming in the original language¹ that there wouldn't be much of a point in doing that.

¹ And perhaps more importantly: it would be highly unlikely that existing code would conform to that subset. So if there's a compiler that can compile my code to efficient GC-free native code, but only if I completely re-write my code to fit an awkward subset of the language, why wouldn't I just re-write the project in Rust instead? Especially since interop with libraries that aren't written in the subset would probably be infeasible as well.

Upvotes: 3

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