memory address search
I'm wondering whether it's possible to somehow search for a specific object instance by checking every possible (used, if that's checkable) memory address. The object wouldn't be accessible otherwise but this way (or it's stored in some unknown instance or class).
Would some Unsafe magic work for that?
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Unknown User•3mo ago
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What if I'm sure that this object isn't garbage-collected
For example because it's handling incoming connections
Wouldn't that prevent it from being garbage-collected as it's method's bytecode is used?
Or if you just once started a new thread
And it always does something but the reference to it is lost
Wouldn't it still be stored as an object in memory somewhere?
Unknown User•3mo ago
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I'd say that running threads are GC roots and therefore not GCed
So I COULD perform a search by like Unsafe#getObject(long address) and check every address to get for example a thread?
That makes me wonder
If I were to replace that memory address with another object
Could I somehow update the thread-cached values
And therefore completly override any object I want?
Even if it's not stored anywhere as a variable
Unknown User•3mo ago
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It does wonders for fast modifying of basically anything
I just don't know about this
what?
you cannot rely on objects being stored at a specific address, objects may be moved at any time
It is a JDK internal class giving you somewhat low level access to more or less raw memory. The memory access methods are deprecated for removal in favor of the Foreign Function and Memory API and
VarHandlesSo it isn't likely that I can find any object by searching through all addresses?
It's deprecated since java 23
But I honestly don't see the reason behind that
ig it would probably work
Unsafe can offer better performance to VarHandles
depends how you are using it
And even if that's not the main concern or the difference isn't significant
VarHandles' main features were added in java 9
So they pretty much are saying "more work if you wanna support all java versions"
Well
Unsafe stuff is probably gonna get removed at some point