Uninitialized memory blocks in VC++

c++ memory allocation
Jeff Hubbard picture Jeff Hubbard · Sep 15, 2008 · Viewed 10.8k times · Source

As everyone knows, the Visual C++ runtime marks uninitialized or just freed memory blocks with special non-zero markers. Is there any way to disable this behavior entirely without manually setting all uninitialized memory to zeros? It's causing havoc with my valid not null checks, since 0xFEEEFEEE != 0.

Hrm, perhaps I should explain a bit better. I create and initialize a variable (via new), and that all goes just fine. When I free it (via delete), it sets the pointer to 0xFEEEFEEE instead of NULL. When I insert a proper check for NULL, as all good programs that manage their own memory should, I come up with problems as 0xFEEEFEEE passes a NULL check without problems. Is there any good way, other than manually setting all pointers to NULL when deleting them, to detect when memory has already been freed? I would prefer to not use Boost simply because I don't want the overhead, small though it may be, since that's the only thing I'd be using Boost for.

Answer

Eclipse picture Eclipse · Sep 15, 2008

When you create a pointer, explicity initialize it to NULL. Likewise after a delete. Depending on the value of uninitialized data (except in a few specific cases) is asking for trouble.

You can save yourself a lot of headaches by using a smart pointer class (such as boost::shared_ptr) which will automatically deal with whether a pointer is initialized or not.

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