[xyzzy_plugh]

You're talking about something that isn't related to efficiency. Copy and pasting, macros, generating code -- none of these preclude producing an efficient solution.

There is nothing in C++ that is inherently more efficient than C.

[dermesser]

Except that more efficient solutions can be implemented much more practically? Solutions that you'd need to bend over backwards for in C?

[xyzzy_plugh]

What does that have to do with efficiency? We don't appear to be debating language ergonomics, but the notion that C is somehow inferior to C++ when it comes to performance.

[humanrebar]

C++ has a lot of compile time programming features that C cannot do practically. There are sometimes alternatives to those mechanisms in C, but they rely on mangling, macros, non-portable tricks, and so on.

On the topic of performance, the best counterargument to C++ from a C perspective would be that hand rolled code generation isn't all that bad in practice. It's just language theorists don't like that approach aesthetically.