pkg-config incorrect about libglib2 version when compiling gtkglext. but correct .pc file is there

[mitchell phillip Laks]

Hi,

How do I troubleshoot the cause of an apparent pkg-config mistake?

I am running sid, and i have the standard gtk2 packages (gtk2, atk pango etc
including the development packages) except for gtkglext. I want to compile the
latest version of gtkglext and gtkglextmm from source.

when i run ./configure for gtkglext all is fine until 

checking for GLIB - version >= 2.0.0...
*** 'pkg-config --modversion glib-2.0' returned 2.8.6, but GLIB (2.12.4)
*** was found! If pkg-config was correct, then it is best
*** to remove the old version of GLib. You may also be able to fix the error
*** by modifying your LD_LIBRARY_PATH enviroment variable, or by editing
*** /etc/ld.so.conf. Make sure you have run ldconfig if that is
*** required on your system.
*** If pkg-config was wrong, set the environment variable PKG_CONFIG_PATH
*** to point to the correct configuration files
no
configure: error: GLib 2.0 not found

However when I look in the directory
/usr/lib/pkgconfig
mlaks <at> workstatio:~$ ls /usr/lib/pkgconfig/
alsa.pc                   gnome-mime-data-2.0.pc  randrproto.pc
atk.pc                    gnome-system-tools.pc   renderproto.pc
audiofile.pc              gobject-2.0.pc          rhythmbox.pc
avahi-client.pc           gthread-2.0.pc          shared-mime-info.pc
cairo-ft.pc               gthread.pc              sm.pc
cairo.pc                  gtk+-2.0.pc             videoproto.pc
cairo-pdf.pc              gtk+.pc                 vorbisenc.pc
cairo-png.pc              gtk+-x11-2.0.pc         vorbisfile.pc
cairo-ps.pc               ice.pc                  vorbis.pc
cairo-svg.pc              inputproto.pc           x11.pc
cairo-xlib.pc             jack.pc                 xau.pc
cairo-xlib-xrender.pc     kbproto.pc              xbitmaps.pc
com_err.pc                lcms.pc                 xcursor.pc
dbus-1.pc                 libart-2.0.pc           xdmcp.pc
devmapper.pc              libcrypto.pc            xext.pc
esound.pc                 libcurl.pc              xextproto.pc
fixesproto.pc             libexslt.pc             xfce4-icon-theme-1.0.pc
fontconfig.pc             libidn.pc               xfce4-session-1.0.pc
fontenc.pc                libpcre.pc              xfixes.pc
fontsproto.pc             libpng12.pc             xfont.pc
fontutil.pc               libpng.pc               xfprint-1.0.pc
freetype2.pc              libssl.pc               xft.pc
gdict-1.0.pc              libxml-2.0.pc           xinerama.pc
gdk-2.0.pc                libxslt.pc              xineramaproto.pc
gdk.pc                    lua50.pc                xi.pc
gdk-pixbuf-2.0.pc         lualib50.pc             xml2po.pc
gdk-pixbuf-xlib-2.0.pc    mad.pc                  xmu.pc
gdk-x11-2.0.pc            ogg.pc                  xp.pc
glib-2.0.pc               openssl.pc              xproto.pc
glib.pc                   pangocairo.pc           xrandr.pc
gmodule-2.0.pc            pangoft2.pc             xrender.pc
gmodule-export-2.0.pc     pango.pc                xt.pc
gmodule-no-export-2.0.pc  pangoxft.pc             xtrans.pc
gmodule.pc                pangox.pc               xv.pc
gnome-doc-utils.pc        printproto.pc

and this is the content of 
mlaks <at> workstation:~$ cat /usr/lib/pkgconfig/glib-2.0.pc

prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

glib_genmarshal=glib-genmarshal
gobject_query=gobject-query
glib_mkenums=glib-mkenums

Name: GLib
Description: C Utility Library
Version: 2.12.4
Libs: -L${libdir} -lglib-2.0
Cflags: -I${includedir}/glib-2.0 -I${libdir}/glib-2.0/include

So what is causing pkg-config to "lie"? Doesnt it look in the
/usr/lib/pkgconfig/glib-2.0.pc file which is correct!
it can't be diversion from the $PKG_CONFIG_PATH variable because

workstation:~# whoami
root
workstation:~# echo $PKG_CONFIG_PATH

workstation:~# exit
logout
mlaks <at> workstation:~$ echo $PKG_CONFIG_PATH

mlaks <at> workstation:~$

also when i check my packages

mlaks at workstation:~$ dpkg -l|grep libglib
ii  libglib-perl                     1.140-1                             Perl
interface to the GLib and GObject libra
ii  libglib1.2                       1.2.10-17                           The
GLib library of C routines
ii  libglib1.2-dev                   1.2.10-17                           The
GLib library of C routines (development)
ii  libglib2.0-0                     2.12.4-2                            The
GLib library of C routines
ii  libglib2.0-0-dbg                 2.12.4-2                            The
GLib libraries and debugging symbols
ii  libglib2.0-data                  2.12.4-2                            Common
files for GLib library
ii  libglib2.0-dev                   2.12.4-2                           
Development files for the GLib library
ii  libglib2.0-doc                   2.12.4-2                           
Documentation files for the GLib library
ii  libglibmm-2.4-1c2a               2.12.0-1                            C++
wrapper for the GLib toolkit (shared lib
mlaks at workstation:~$



Thanks,
Mitchell Laks