Is it bad practice to use C features in C++?

Question

For example printf instead of cout, scanf instead of cin, using #define macros, etc?

Answer 1

It depends on which features. Using define macros in C++ is strongly frowned upon, and for a good reason. You can almost always replace a use of a define macro with something more maintainable and safe in C++ (templates, inline functions, etc.)

Streams, on the other hand, are rightly judged by some people to be very slow and I've seen a lot of valid and high-quality C++ code using C's FILE* with its host of functions instead.

And another thing: with all due respect to the plethora of stream formatting possibilities, for stuff like simple debug printouts, IMHO you just can't beat the succinctness of printf and its format string.

Answer 2

You should definitely use printf in place of cout. The latter does let you make most or all of the formatting controls printf allows, but it does so in a stateful way. I.e. the current formatting mode is stored as part of the (global) object. This means bad code can leave cout in a state where subsequent output gets misformatted unless you reset all the formatting every time you use it. It also wreaks havoc with threaded usage.

Answer 3

For allocations, I would avoid using malloc/free altogether and just stick to new/delete.

Answer 4

Coming from a slightly different angle, I'd say it's bad to use scanf in C, never mind C++. User input is just far to variable to be parsed reliably with scanf.