How does Portage handle updates, USE-flags and dependencies?

[entob]

I have a question on how Portage handles updates, USE-flags and dependencies.

1. I emerge a program with USE-flags that requires dependencies.
2. Later I wan't to update that program, but this time I have removed one USE-flag. Now one dependency is no longer is needed by the program.

Will Portage remove the no-longer-needed dependency and if so; will Portage still remove this dependency even if other programs use it?

[superjaded]

Portage does not yet have any reverse dependancy checking, atleast none that is recommended to use.

Alternatively, you can do emerge -p depclean which basically unmerges all programs that are not found in the world file and are not dependancies on programs in the world file. However, I would REALLY be careful about using this because the one or two times I've run the thing, it caught quite a few false-positives.

[entob]

Is there a way of checking if this specific dependency is used by other programs?

[superjaded]

try this commandline using qpkg from the gentoolkit ebuild:

[Given M. Sur]