pkg-config inconsistent

[wakedoe]

I have run into a problem trying to install rrdtool onto CentOS. When installing the dependencies pkg-config keeps running into odd issues. For example

$ pkg-config --exists glib-2.0; echo $?

will return 0 indicating that glib-2.0 doesn't exist

$ pkg-config --modversion glib-2.0

returns the correct glib 2.x version that is installed

$ pkg-config --cflags glib-2.0

returns the correct compiler flags. Besides the .pc files in its path does pkg-config have any other configuration files? I'm really not sure where to go from here.

[wakedoe]

wow talk about not RTFMing...

[wakedoe]

So here's the actual issue

./configure complains about missing cairo when building pango for example

but setting the libs and cflags manually

$ export CAIRO_CFLAGS=`pkg-config --cflags cairo`
$ export CAIRO_LIBS=`pkg-config --libs cairo`

does the trick and it proceeds without fault. I've set PKG_CONFIG_PATH to /usr/local/lib/pkgconfig which contains the package files for cairo and other libraries and obviously pkg-config sees that when invoked directly but not through the configure script. I'm pretty new to nix and I'm STUMPED.