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How to determine how many heap is left?

Posted by Willem on November 30, 2008
Is there a way for me to determine how many heap is available?

I frequently kill and start threads. I know that (if the scheduler is already running) when i give a command to start a task and there is not enough heap, the OS would not start the task and just continues (what is fine).

But i noticed that sometimes there is enough heap for an task to run, but then it crashes because the task itself tried to create a queue while there was not enough space left in the heap.

At that very moment, the whole OS stops working, even the higher level tasks.

I want to prevent this from happening by first checking the space left in the heap. Is that possible?

RE: How to determine how many heap is left?

Posted by Dave on December 1, 2008
It depends which version of the heap you are using. Three examples are given, heap_1, heap_2 and heap_3, but you can also provide your own. Heap_1 and heap_2 have variables you can inspect to see how much is left. Heap_3 uses malloc and free so it is not as easy.

When you create a queue check the return value to see if the queue was actually created or not. This will enable you to prevent the app crashing when you run out of heap.

Also consider fragmentation if you are creating and deleting resources all the time.

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