[zephen]

The middle approach is the only one that is not lock-free.

The first approach is lock-free, but as the author says, it wastes an element.

But here's the thing. If your element is a character, and your buffer size is, say, 256 bytes, and you are using 8-bit unsigned characters for indices, the one wasted byte is less than one percent of your buffer space, and also is compensated for by the simplicity and reduced code size.

[fullstop]

I've used the "Waste an element" one for ages on microcontrollers where I don't want to deal with the overhead in an ISR.

[zephen]

Agreed.

The article author claims that the "don't waste an element" code is also more efficient, but that claim seems to be based on a hard-on about the post-increment operator, rather than any kind of dive into the cyclometric complexity, or even, y'know, just looking at the assembler output from the compiler.