Hello. I have multilib linux system, 32-bit libraries are installed into /usr/lib and 64-bit libraries - into /usr/lib64
After configuring popt-1.16 via CC="gcc -m64" CXX="g++ -m64" ./configure --prefix=/usr --libdir=/usr/lib64 produced Makefile contains instructions to install popt.pc into pkgconfigdir = /lib/pkgconfig which will be "/usr/lib" in my case, but not "/usr/lib64" - as I want by specifying "--libdir=/usr/lib64". Libraries (libpopt.a, libpopt.so) and libtool lbrary file (libpopt.la) installed correctly into /usr/lib64. This behavior differs from other projects, for example http://ftp.gnu.org/pub/gnu/libidn/libidn-1.18.tar.gz which installs libidn.pc into pkgconfigdir = /pkgconfig being configured in the same way. So I suppose popt.pc should be also installed into pkgconfigdir = /pkgconfig but not into pkgconfigdir = /lib/pkgconfig otherwise 64-bit popt installation breaks my previous 32-bit popt installation. Regads, Michael.