There are actually two debug modes:
1. -D_LIBCPP_DEBUG2 or -D_LIBCPP_DEBUG2=1
This is a relatively expensive debug mode, but very thorough. This is normally what you want to debug with, but may turn O(1) operations into O(N) operations.
2. -D_LIBCPP_DEBUG2=0
This is "debug lite." Only preconditions that can be checked with O(1) expense are checked. For example range checking on an indexing operation. But not iterator validity.
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@187369 91177308-0d34-0410-b5e6-96231b3b80d8
