Often you can see answers like Avoid using C libraries in your C++ code or This can be rewritten using STD/Boost in pure C++.I understand C++ produces more maintainable code and has many advantages, but is it actually bad using C libraries when performance is a priority? I mean writing in what is sometimes  called C-with-classes.Ive been developing a text file parser with both C and C++ versions and the C one was considerably faster. What i would like to know is if using C libraries in C++ has hidden drawbacks apart from the obvious ones like making the code less maintainable.
Drawback of mixing C++ code with C for performance purposes
c++;c