[gpderetta]

As you explained, the debugging mode for STL is well beyond normal debugging mode (i.e. no optimiziations, all debug symbols). It explicitly changes complexity guarantees of the stl to catch issues with iterator invalidation and other nasty bugs. As such it adds a considerable runtime cost to any use of the STL.

In a way it is comparable to the overhead of the sanitizers available in other compilers.

IIRC MS chose to enable it by default in debug mode as part of their effort of fortifying unsafe C and C++ code against security bugs, but of course it has a large penalty.

libstdc++ has a similar debug mode, but it is disabled by default, as, in addition to be more expensive, it also breaks the ABI.