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Is it possible for a Non-Interpreted language to have a Garbage collector. Interpreted languages have the Interpretor executing the Program line by line so the Interpretor might just as well provide a runtime with a GC. But is it possible to have a Garbage collector for any other language without building the GC in your code itself ?

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    I wonder if you're assuming a false dichotomy between "interpreted" and "native". Java and C#, for example, are neither "interpreted" nor "native" - they run (essentially) in a VM, but from an IL. Commented May 6, 2009 at 10:31
  • Can you please Explain more :? Commented May 6, 2009 at 10:36
  • For that conversation, see the comments on my reply. Commented May 6, 2009 at 10:51

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Garbage collection only requires the pointer variables be marked special way so that the runtime can identify them and use for garbage collection. It has nothing to do with interpretation/compilation, but instead requires special runtime and storing additional data with each variable.

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Well Interpreted languages give you a Run-Time. Atleast it is easier for the Interpretor to work as a Run-Time and run a garbage collector too. Any Native language will have the OS as the runtime ? And hence no GC ?
GC and interpretation are unrelated to each other. Yes, it's potentially easier for an interpreted language to have garbage collection, but non-interpreted languages can do this too. OSes usually don't have embedded support for garbage collection, but many language runtimes have.
And even without marking the pointer variables in a special way you can have so-called conservative GC that treats all memory contents as potential pointers. See Boehm's GC in the other answer.
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Well, .NET languages (that emit to IL - C#, VB.NET, MC++, etc) aren't interpreted (especially if you use NGEN) - and has full garbage collection.

Likewise, Java.

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I believe HotSpot interprets for the first pass (unless it sees a loop, or something like that) but will then JIT compile. At that point it's definitely not interpreted.
@Marc: I'd say that Java source code is never interpreted, but Java bytecode may be. In real life it's interpreted briefly and then JIT compiled. In .NET, IL is never interpreted - but Mono has an IL interpreter. Note that JavaScript isn't always interpreted either - modern JS engines do JIT compilation.
@Jon - cheers for the clarification (although see JET/gcj). Actually, MS .NET has an interpreter too - Micro Framework.
So to summarise: Java/C# is compiled to bytecode/IL. That bytecode/IL is usually (most of the execution time, most environments) JIT compiled; occasionally it's interpreted. Calling Java and C# "interpreted languages" is a mistake though.
Sometimes it's interpreted. But not very often. The bare statement of "Java is interpreted" is very misleading.
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Yes - http://www.hpl.hp.com/personal/Hans_Boehm/gc/

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For an actual implementation in a compiled language, in this case C and/or C++, see the Boehm GC at http://www.hpl.hp.com/personal/Hans_Boehm/gc/

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Haskell has garbage collection, whether it's compiled to native code or interpreted.

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The new C++0x includes features that make implementation of garbage collection easier. See this interview for example.

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Yes.

C++ with a smart pointer implementation will garbage collect as the smart pointer reference counts go to zero.

You have garbage collection. You did not build it yourself.

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I think that the question is about tracing garbage collection, and refcount is not a substitute.
That's not garbage collection. Connect several objects such way that they have a cycle and they are never destroyed unless you break the cycle manually.
@sharptooth: take it up with the rest of the world, not me: codeproject.com/KB/cpp/automatic_gc_using_sp.aspx
@dmitry-vk: The question asked about writing a GC, not about "tracing" vs. "refcount" as a technique for detecting unused pointers.
@sharptooth -- smart pointers have limitations. However, they are garbage collection and they are code you don't write. Again, if you don't like this definition, you'll have to take it up with a lot of people. Search for smart pointer garbage collection and you get a lot of hits.
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Objective-C 2 has garbage collection now, and there are garbage collection libraries available for C++ as well.

I think it's possible as long as there is it the language allows you to inspect objects so you can traverse the object tree.

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Can you please explain how it works. This is like attaching a GC Thread alongwith your program isn't it ?
Separate thread is unrelated to GC -- that just happens to be the way Java does it. Most C++ (and Objective-C) handle it at delete time when the ref count goes to zero.
Objective-C 2 has real garbage collection; the runtime traverses the object tree. Refcounts are ignored when garbage collection is enabled. I believe it's part of the event loop, but I'm not sure.

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