Heuristics for better handle leak report

_From [zhao...@google.com](https://code.google.com/u/106321947286816917100/) on November 07, 2013 14:11:56_

Dr. Memory has handle leak report feature (-check_handle_leaks), however, the application may left thousands of handles open, some on purpose and some by mistake, which makes handle leak report useless.

We need apply heuristics to filter the error reports.
Two heuristics to be added:
1. If there is a callstack that creates lot of handles that are not closed, it should be reported. Even these handles are left open on purpose, they should be paid attention to, because it may still use up all handles.
1. If there is a callstack that creates many handles, some are closed but some are not, it should be reported. Basically, if a handle is closed before, it should be closed again.

We might not want to use the exact same callstack match. For example, if a callstack is ABCDEFX, another callstack is ABCDEFY, we might want to consider them the same callstack. So what's the right heuristic to compare two callstacks? Maybe the longest common subsequence ( http://en.wikipedia.org/wiki/Longest_common_subsequence_problem)?

_Original issue: http://code.google.com/p/drmemory/issues/detail?id=1373_