The worst parts of Sepples

The standard "Streams". Its name hints at fast, intuitive interface that should simplify the Input/Output abstraction.
In reality its a template monster thats slow and extremely hard to use, beyond the simplest demo programs.

My favourite part of Sepples streams is formatter objects. Either, you have to input the correct formatter every time you print something, define an informal standard state you return to after using any non-standard format, or risk nonsense output in random places.

It's absolutely amazing how streams are not only a useless layer on top of stdio but actively harmful to any project using them. An API worthy of the likes of INTERCAL.

>>2
Passing stream objects to functions and receiving them is alot of pain.
Also the lack of std::bin for binary output in this huge library that has dozens of output states, unicode support and custom callbacks for stream events( http://www.cplusplus.com/reference/ios/ios_base/register_callback/ ) .

>>1
The <locale> library is the worst, imo, with the streams coming in second.

For common locale transformations, C++ locales is generally 10x-100x slower and more bloated than the C locale.h and cctype.h library functions.