1. Just because things aren't done "the way you would do them" doesn't mean they're "bad" or "wrong".
2. If you're not on a solo project, I've found writing correct but less "clever" code to help shorten ramp-up time for new devs and be more beneficial to future maintainability of the code-base and system.
TL;DR; Swapping values by XOR'ing may look elite and clever but hurts you in the long run.
Further, I would consider Linus's one-liner 'indirect=...' to be 'clever' code.
If I were reviewing it, I would want it expanded into more obvious code as it requires too much cognitive overhead to parse.
I don't find the pointer syntax that difficult to reason with.
How would you expand the code?
People will and are arguing that "it is kernel code, it should be complicated" but I really think this is backwards. Because it is low level and debugging is really cognitively intense and difficult at this level the code should be even clearer and easier to understand.
This code is inherently too complex. it should be simplified
That is, not every project has "shortening ramp-up time" as a priority. In quite a few cases non-trivial code doubles as filter for less skilled devs.
An OS kernel is going to be a very complex piece of code (ignoring microkernels) because what it does is complex. But that is all the more reason to keep the code as straightforward as possible. (There are still going to be times where code is not straightforward due to inherent complexity of the problem, or performance considerations, or portability, ...)
Right, until the less skilled dev it's you, months later after you moved on to other stuff, and have to get back and fix some clever shit you wrote but don't understand anymore.
Unless you're doing numeric or performance critical work, code should be optimized for readability and maintainability.
I was talking about the more broad idea of knowingly writing clever code to raise the entry barrier for new devs. Or just writing clever code for whatever the reason. It's almost guaranteed to backfire, to new devs who will have to maintain it or to yourself, when you will have to read it in a less smart moment.
Also, "less skilled devs" are just people that are still learning. We've all been there.
Projects should be accessible to new developers with appropriate skill set, which is inherently defined by the projects' complexity.
https://en.wikipedia.org/wiki/XOR_swap_algorithm#Reasons_for...