I think the summary gets most of it. Compiling xfce4-mixer, I get link errors as follows: > xfce4_mixer_plugin-xfce-volume-button.o: In function `xfce_volume_button_update': > /home/seanni/install/xfce4-mixer-4.8.0/panel-plugin/xfce-volume-button.c:435: undefined reference to `XFCE_PANEL_IMAGE' > xfce4_mixer_plugin-xfce-mixer-plugin.o: In function `main': > /home/seanni/install/xfce4-mixer-4.8.0/panel-plugin/xfce-mixer-plugin.c:116: undefined reference to `xfce_external_panel_plugin_new' My system is Slackware x86_64 (with multilib support for compiling 32-bit programs, although my expectation is that shouldn't be an issue here). I had out-of-the-box xfce 4.6 which I upgraded to 4.8; ran into this issue when upgrading the various xfce apps to match. Have encountered the error with: - xfce4-mixer 4.6.1 - xfce4-mixer 4.8.0 Have not tried with any version other than these two. - xfce itself is installed with prefix /usr - tried running configure with --prefix=/usr and --prefix=/usr/local ; no change - tried running configure with --libdir=/usr/lib64 and without ; no change Peeking into the makefiles, I notice that it is linking against libxfce4panel-1.0 but not libxfce4panel -- however looking through the header files installed into /usr, xfce_external_panel_plugin_new at least is only defined in the latter. Editing panel-plugin/Makefile to add this library eliminates the one error message, but not the other.
Multilib could indeed be an issue here because the build process will attempt to link 32bit libraries if you're not careful; note that --libdir has no effect on where the build *looks* for libraries but rather it affects where the build *installs* the libraries. Unless you can provide more information, I'm closing this as invalid given that I've successfully built all versions of the mixer on multiple versions of Slackware without any issues at all.