OTOH if not for C compatibility we would not have this discussion, since we would most likely never heard of C++.
In modern C++ it is very much possible to write fast and safe code, but the tradeoff is now put into the amount of stuff the developer needs to know to be productive (Which in my experience isn't as bad as people like to go on about on here/reddit, even if it still pretty shoddy)
Thats a bit unfair. A recent headache for my C++ project was mixing audio buffers. The buffers are cached to avoid repeated reads, the channel count differs, the sample rate can differ, the output rate can differ, and mixing has gain limiters applied etc. Lots of buffers, lots of copying, lots of boundary cases (eg. sample #1 doesnt start until t=100ms, sample #2 ends before sample #1, etc).
I struggled for days getting all the buffer copying right (raw pointers to many interrim buffers). You may think that my problems were due to using "crap c++ in unidiomatic way". However, I challenge you to find a better, and as efficient method to accomplish the same goal. The end MixAudio() function looks like plain old C code from the early 80's, but how else can you tackle this problem in a modern way?
It seems like you struggled with math (indexing logic) rather than C++.
> how else can you tackle this problem in a modern way?
You could try to write an iterator that takes into account sample rate, channel count, etc. That way the logic for handling buffer formats and iteration over samples is encapsulated into a single reusable component.
Efficiency should be roughly the same, especially given that you can optimise loops (and other code) with just as much access.
Ah, yes. I think they called it "C".