On Fri, Aug 22, 2014 at 09:28:05AM +0100, Peter Maydell wrote: > On 22 August 2014 09:20, Daniel P. Berrange <berra...@redhat.com> wrote: > > Distros will install pkg-config .pc files for non-native architectures > > in a different location normally. The supported / recommended way to > > tell pkg-config to look in these alternative dirs is to set the env > > variable PKG_CONFIG_LIBDIR. This replaces the built-in default search > > directory that looks for native. > > > > So on a Fedora / RHELL system, to make pkg-config use 32-bit libs you > > want to set > > > > PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig > > > > which replaces the default location of /usr/lib64/pkgconfig. This is > > the same thing you'd need to do to build QEMU for say, mingw32 where > > you must set something like > > > > PKG_CONFIG_LIBDIR=/usr/i686-w64-mingw32/sys-root/mingw/lib/pkgconfig/ > > Yes, but this should be done by the i686-w64-mingw32-pkg-config > wrapper IMHO. (That's how I have my mingw setup configured, > anyway.)
Sure if your distro wants to rebuild the pkg-config binary for each arch that is a valid approach too, but it is by no means required in order to get non-native builds working. > > Note, i say PKG_CONFIG_LIBDIR here, *not* PKG_CONFIG_PATH. The latter > > variable adds the default search path - you want to stop it looking in > > the default search path completely because it is the wrong arch, so > > must use PKG_CONFIG_LIBDIR > > Interestingly, Debian's cross-compile pkg-config wrapper > (aarch64-linux-gnu-pkg-config etc) sets PKG_CONFIG_PATH, > not PKG_CONFIG_LIBDIR. Maybe that's a bug, but it works... Yes, that would be a bug. Consider if you have mistakenly only installed the 64-bit dev package for libusb and not the 32-bit package. Now the 'libusb-1.0.pc' file will only be present in the directory /usr/lib64/pkgconfig but not in /usr/lib/pkgconfig. If you used PKG_CONFIG_PATH to point to the 32-bit directory, then it won't find the 32-bit libusb-1.0, so will fallback to looking in the 64-bit directory and repo the 64-bit version which is definitely not what you want. That'll lead to pain & suffering with wierd build and/or link errors. If you used PKG_CONFIG_LIBDIR then you'll get an immediate error from pkg-config telling you the 32-bit libusb-1.0 package was not installed. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
