Add section on error reporting to coding guidelines

[kinkie]

No description provided.

[yadij]

Suggested change

	To check system-leve invariants, where a failure needs to terminate Squid, use `xassert(condition)`
	To check system-level invariants, where a failure needs to terminate Squid, use `xassert(condition)`

[yadij]

There is also static_assert for compile-time invariant. Alex has some very specific requirements about wording the descriptions there.

It would be useful to mention what "report" means: where, how, and what does it look like for each of these cases?

Also, IIRC Alex had a definition of "invariant" that did not quite line up with C/C++ standard definition of the terminology. I came away from the Must() vs Assure() discussion thinking there was a disjoint paradigm in play.

[rousskov]

I welcome this attempt at documenting error handling and invariant checking guidelines. Related code is often problematic, and documentation can help reduce the number of problems and correction overheads.

There is at least one bug and several problematic statements in the current version. It is also very difficult to derive the correct decision making algorithm from the proposed sentences. As Amos has noted, it is probably best to cover static_assert cases here as well.

I will find the time to rewrite this. I do not recommend making changes until then.

[kinkie]

I welcome this attempt at documenting error handling and invariant checking guidelines. Related code is often problematic, and documentation can help reduce the number of problems and correction overheads.

It's more than this. Coding Guidelines can (and should) feed LLMs, both code-writing and code-reviewing ones.

There is at least one bug and several problematic statements in the current version. It is also very difficult to derive the correct decision making algorithm from the proposed sentences. As Amos has noted, it is probably best to cover static_assert cases here as well.

I will find the time to rewrite this. I do not recommend making changes until then.

Feel free to improve