HEAP [example.exe]: "Number of free blocks in arena (69) does not match number in the free lists (68)"

This is a VERY difficult problem were having when we exit the main application in runtime. It does not come up in DEBUG mode. Im using Visual C++ V6 Service Pack 6 under Windows XP Pro.

Error Message: "HEAP:[example.exe] Number of free blocks in arena (69) does not match number in the free lists (68)

When it exits the main application the above error message comes up after it completes the exit instance in the main application.

Has anyone got any ideas what this error means and how to diagnose and fix the problem. The main application is very big.

Many thanks

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carribusConnect With a Mentor Commented:
The last time I heard the term "arena" was back in the good old DOS days when one had to know about "arenas" of memory for virtual memory managers and so on. I went and did some reading in the MSDN, and it seems that Windows has 2 different "versions" of memory arenas, specifically one version for Win9x and ME, and another for the NT based Windows (for obvious reasons).

Coming back to your question, I don't have an answer for you, but I do have a few suggestions and queries.

1. In your application, are you performing any 'unusual' memory operations? perhaps dipping down into the metal with a few _asm { } blocks of code?
2. Do you have your own memory manager running in this app? Does it do any Virtual Memory calls during the execution of the app? If yes, make sure that all the calls are terminated correctly and all handles are closed.

Thats about all I can think of. If I find anything else, I'll post.
Mike38Author Commented:
Many thanks for the quick reply.

I don't do any unsual memory operations like _asm and I don't use my own memory manager app. I also make sure the calls are terminated correctly and handles closed.

Very strange bug error message.

grg99Connect With a Mentor Commented:
You're probably zapping some bytes past the end of one of the blocks you allocate.   I'd use some heap debug tool that checks for this.  Or you can roll your own malloc() and free() wrappers that check for this.

jkrConnect With a Mentor Commented:
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