There are some issues with that, that could probably be resolved if one has time to spend on them. But the problem is that that would require all other libraries that use strings and such in their api to be compiled with libc++ (boost is a notable example, but many other big libraries have little fear for abi-incompatibilities :) ). So I've actually tried to avoid that hole. And many other opencv-users might, so both cases should be supported I guess. Anyways - I guess it is not a big deal to keep using stdint.h (with a __clang__ #ifdef) until most libraries have made a proper switch to be buildable with libc++.