No. I'm talking about adding the check to reject NULL. Then you don't have to spend time justifying or figuring out why a NULL can't turn up here.
My proposition is that "it's silently ok" isn't likely enough, which is in line with your position on "don't extend the contract to accept null". So what's left is crash, or something worse.
So if those are your choices, don't waste time justifying that a null can't get there, just add a check to ensure you get the better behaviour. It takes seconds.
You are requiring yourself to find a valid outcome for an input that doesn't make _any_ sense in the context of what your application is meant to achieve. How is that not a Sysiphean task?
You're actually pruning the valid state space; before, when the null value is passed to the function, there are more operations performed that have uncertain consequences. If you assert-and-fail when you get the null input, you've pruned those states.
"Because no one is expecting it to work if a null is passed", so you can do whatever. If you write an assert for every pointer passed to every function, that will be a lot of asserts, for pretty much the same outcome in practice. Asserts are just marginally more ergonomic when they trigger, but are a nuisance in the code often. So my position is to use them judiciously, but not overdo it, be instead focused on the actual task.
When the lack of non-null assertions is an actual problem during development, you have much larger structural issues.
I thought so too, for many other things, and did so too in practice. Then I was doing thousands of little tasks in order to improve "security" and "correctness" and "proving everything", and never got to actually do anything useful, and my code became bloated to the point it didn't get to do much useful work.
Now I'm more considerate, trying to weigh everything in the larger context, is it REALLY required to get my job done?