By "negative" idioms I'm mostly referring to stdio, string.h (except for memcpy/memmove of course), goto-based cleanup, void* based generics, overuse of macros and a certain fondness for global mutable state in a lot of classic C codebases.
Disagree here. Given the language's limitations, everyone of the idioms you list has its place and uses. They are just a way of structuring code for different abstractions.
That's not what i was saying (it's a given). After all C++ was invented to provide programmers with a large number of features that would allow them to express abstractions naturally and directly rather than building them up with all the basic plumbing that you would need to do in C.
However there is a huge amount of C code and programmers who would like to move to C++ and it is for them that the techniques of C coexisting with C++ are very relevant. There can be no wholesale rewrite of the code into C++ but a gradual rewrite module by module and as needed. Using C++ as a "better C" is the path here.
