Re: [gentoo-user] Re: Updating libpng: another lib tool cockup?

[Paul Hartman <paul.hartman+gentoo@gmail.com>]

On Mon, Sep 19, 2011 at 9:58 AM, Allan Gottlieb <gottlieb@nyu.edu> wrote:
> OK.  But the claim was that: if
>   revdep-rebuild
> with no argument found nothing to build, then
>   revdep-rebuild --library <some-library>
> will find nothing.

I think what everyone (except Michael S) seems to be confused about is:

Normal revdep-rebuild (with no options) looks for broken shared
library dependencies and rebuilds them. If you run it again, it won't
rebuild anything, because the dependency has been fixed.

Using the --library switch, however, it looks for everything built
against that library, regardless of whether or not the dependency is
broken, and rebuilds it. If you run this command 10 times in a row
it'll rebuild the same libraries 10 times.

Presumably, there are cases (like libpng) when it is desirable to
rebuild dependencies but they aren't "broken" in the way that
revdep-rebuild normally can detect. So using --library will
brute-force rebuild everything that depends on that library, just to
make sure they are built against the new version.

Moral of the story; if an ebuild tells you to revdep-rebuild
--library, do it. :)