Help, My Java Object Vanished (and the GC Is Not at Fault)

(arraying.de)

76 points by todsacerdoti 2 weeks ago|9 comments

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mands 5 days ago

Great read, both in terms of content, but also the approach to diagnosing the issue and debugging in general.

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cluckindan 6 days ago

Check your code block CSS, the font sizes are all over the place on mobile (iOS).

By ”you” I mean anyone who has a blog and uses code blocks.

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ErikCorry 2 weeks ago

Nice!

Why malloc? Surely this is an on-heap object, not malloc allocated?

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tialaramex 5 days ago

I think you've got yourself confused. The heap is what malloc is allocating. So it's like you said "Surely this is somewhere in Europe, not France?" or "Surely this is a round shape, not a circle?"

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comex 5 days ago

Not when we’re talking about a JVM, which has its own heap that does not use malloc.

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tialaramex 5 days ago

The JVM is of course just software. In this case it's mostly software written in C++ and that software allocates "its own heap" using uh... malloc

https://github.com/openjdk/jdk/blob/master/src/hotspot/share...

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ErikCorry 2 hours ago

I'm actually pretty surprised if the JVM uses malloc to allocate the heap. V8 uses mmap, never malloc.

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pjmlp 2 days ago

In the specific case of the OpenJDK, there isn't the one JVM, rather a standard[0], like in ISO languages, with a reference implementation to go along it,

https://en.wikipedia.org/wiki/List_of_Java_virtual_machines

And the list doesn't include all, e.g. PTC (https://www.ptc.com/en/products/developer-tools/perc)

[0] - https://docs.oracle.com/javase/specs/index.html

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1718627440 2 days ago

malloc is also not a specific implementation, but a standardized interface for allocating on the heap.