Regarding exceptions, I was taught that function signatures in header
files are an exception too. I don't mind either way, but if the rules
disagree with the current practice, we should make that explicit.

Actually, I can't recall ever hearing about a soft limit. Though, I like
the idea. I tried to formalize something like that once with the notion
of a "visible width" during a [coreboot] discussion. Quoting myself here
in case somebody is interested:

> [...] I see three
> major cases that people care about:
>
>  1. Function signatures,
>  2. Code lines and
>  3. Code lines containing string literals[1].
>
> Let's assume 72 chars of visible width (line length minus the inden-
> tation) is enough for code lines. If we say two additional indentation
> levels are always reasonable (a third might be too, here and there) we
> would be at 96 chars.
>
> So I would compromise as follows:
>
>   o Set a hard limit around 100 chars (96 would be a nice number).
>   o If a line doesn't contain a string literal, recommend a
>     visible width <= 72 chars.
>
> Nico
>
> [1] I think we should treat the latter two separately because you can
>     easily argue that lines with a string literal might get too long but
>     if you apply the same rules to regular code, you'll get all the
>     crappy stuff (too many levels of indentation, unnecessary long, less
>     distinctive identifiers etc.).

Full message here[2]. That would only apply to the bulk of the code and
comments. For me, carefully hand-formatted passages (like tables) are
always an exception.

Nico

[2] https://mail.coreboot.org/pipermail/coreboot/2018-May/086834.html