BUILDLINK_ABI_DEPENDS in practice

["Sijmen J. Mulder" <ik%sjmulder.nl@localhost>]

Hi,

Today I was updating some packages, one of them devel/libxlsxwriter.
While it's only a patch version upgrade, it adds fields to public
structs so I'd have to consider that an ABI-breaking change.

When I read the docs:

> ...changes to BUILDLINK_ABI_DEPENDS.pkg are more common. The variable
> will need to be updated every time the major version of one of its
> shared libraries is changed, or any other change where a binary built
> against the previous version of the package will not run against the new
> version any longer.
 ~ https://www.netbsd.org/docs/pkgsrc/buildlink.html#updating-buildlink-depends

it seems to me that I'd have to bump ABI_DEPENDS (and revbump, just
math/sc-im in this case). That makes sense, because you wouldn't want
to use a program linked against the old library then.

However, looking at the pkgsrc commit history to confirm that this
really is correct, I find that in practice these variables hardly get
bumped at all, even when ABI compatibility seems to be broken.

Any guidance?

Sijmen