bug#8219: Effect of deletions on indirect buffers (Bug#8219)

[Stefan Monnier]

> This makes a lot of sense, but your description seems to point out
> that the implementation does not behave according to the docs: if
> markers are (or should be) relocated in sync as result of insertion
> and deletion, the same should happen with PT, BUF_BEGV, etc.

Actually, indirect buffers keep their point and narrowing in real
markers.  So when they get "active" the BUF_PT, BUF_ZV, etc... get
updated, but until that time, BUF_PT and friends may hold invalid data.
I.e. any place where we use BUF_PT on something else than
current_buffer, we have a bug waiting to happen unless we know for sure
that that buffer is not indirect.


        Stefan