C/C++ Heap Checking

Hello

Are there any guides as to how the heap works?
Are there any tools that can walk the heap showing allocated and freed memory?
Does the heap attempt to reuse trapped free space first? ie before its current size/free pointer?

I have an App that uses a library that runs for several days slowly increasing the wimp slot until it exhausts the wimp slot.
My library log is currently 405M and a little tedious to wade through.
I’ve written tests for the library and can’t replicate the effect as yet.

I’ve got a version of Fortify & Memcheck to try but don’t suspect they’ll show anything extra.
Any suggestions.

Cheers
Ron

I’m assuming you’re using the shared C library? There are some comments in the source code which describe the overall behaviour.

Are there any tools that can walk the heap showing allocated and freed memory?

I’m not aware of any. You might have to go down the route of writing your own wrappers for malloc/free so that you can track the info manually (or find a wrapper elsewhere on the internet).

For checking whether it’s a memory leak, you could just keep a count of how many instances of each object type are currently allocated. Although this might not work so well with variable-length objects (e.g. data buffers which can grow)

Does the heap attempt to reuse trapped free space first? ie before its current size/free pointer?

Yes, it should do. However it does coalesce free blocks in a lazy manner, which looks like it might cause unnecessary heap growth in some situations

My library log is currently 405M and a little tedious to wade through.

Rather than waiting for the wimp slot to hit 512MB limit, you could modify the app so that it kills itself much sooner, e.g. 16MB.

Thanks for replying Jeffrey.

I’m assuming you’re using the shared C library? There are some comments in the source code which describe the overall behaviour.