pkg-config only works for development libraries, so this is not the correct way to determine whether a certain (non-dev) library is installed on a user's system.
From: arnold@arnoldarts.de
Subject: Re: [FFADO-user] [I'm a user and need support] JACK doesn't see PHASE X24
Date: September 13, 2009 7:07:50 PM GMT+02:00
To: ffado-user@lists.sourceforge.net
On Sunday 13 September 2009 16:06:54 Eric Boon wrote:
Following up on my own mail, regarding ffado-diag:
I also tried 'ffado-diag', but the output of that one was rather
confusing. It complained about a number of packages not being
installed although they are there.
That's because there's no package information stored. ffado-diag tries
to get the info via pkg-config, but of all the packages installed on
my system, only 5 or so actually shipped with the info that pkg-config
reads. Ergo: pkg-config is not a reliable way to detect whether
certain libs are installed or not - at least not on Debian.
That is because the *.pc files are in the development packages as it is meant
for development. Probably not a good idea to check for libraries on a user-
system with a tool that "only" gives library-and include-paths for devs.