If the default memory manager for FP creates a heap for each thread, what happens if an object is created in one thread and freed by another ? Also, do calls to New () allocate space on the thread heap or just allocated by the OS ?

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Terry Mead schrieb am So., 17. Juni 2018, 07:45:

If the default memory manager for FP creates a heap for each thread, what happens if an object is created in one thread and freed by another ?

If I remember correctly the memory becomes part of the thread's free list that freed the memory. (Though I could be wrong here)

Also, do calls to New () allocate space on the thread heap or just

allocated by the OS ?

All Pascal memory functions are handled by the heap manager. So yes, it's the thread's heap.

Regards,
Sven

Terry Mead wrote

If the default memory manager for FP creates a heap for each thread,

Define "a heap for each thread".

what happens if an object is created in one thread and freed by another ?

It causes a slight performance penalty and memory usage increased as the memory block is available later for re-use.

No. It is added to the "wait for free" queue of the thread which initially allocated it.

Florian Klämpfl schrieb am So., 17. Juni 2018,
10:47:

Ah! That's how it was! 🤦‍♀️

Regards,
Sven

So, excluding the performance penalty, this is not a problem?

Why should it be a problem?

It is not a problem it just makes it a bit tricky tracking memory usage because of the delay between releasing the memory and it the reported heap usage decreasing.  I haven't had a good look at the source but maybe there is some way to take these pending releases into account. Thanks for your input.

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Terry Mead wrote

It is not a problem it just makes it a bit tricky tracking memory usage because of the delay between releasing the memory and it the reported heap usage decreasing.

Just install your own heap manager which is a wrapper around the current one and track allocations/deallocations. FPC does not do this because these values have no real meaning on a multi threaded/multi process system and because it must be done by atomic operations which slow down things.

I haven't had a good look at the source but maybe there is some way to take these pending releases into account.