I've use the CRT leak detection for years, but lately our app needs to call waveOutGetNumDevs(), and as soon as you do this, leak detection breaks and no longer outputs memory leaks.

I've documented it here:

https://connect.microsoft.com/VisualStudio/feedback/details/658899/waveoutgetnumdevs-prevents-memory-leak-detection-output


I've also seen instances where calling gethostbyname() breaks leaks detection as well, although I don't have a good reproducible test case yet.