Sometimes SWI-Prolog lacks features or packages because the required dependencies were not available while compiling the system from source. Installed features and packages can be checked using check_installation/0 (requires SWI-Prolog 7.1.10 or later). Issues found are reported with a link to a wiki page describing the consequences and often point to a missing development library. Fixing this takes two steps.

1. Find and install the library for your OS.

   Linux

   Check out info on your distribution or use the package manager to find and install the library. Make sure to install the development version of the library. On Debian/apt based systems, development versions typically have the suffix -dev. On Redhat/rpm based systems the suffix is often -devel.

   MacOS

   Use Macports or Brew to find the library and install it.

   Windows

   See README.mingw for downloading and installing dependencies.

2. Redo the build. If you have not much experience, the best option is simply to redo the whole build.

   % make distclean
   % ./build

   Examine the log info in configure.out and make.out. If you do not understand why a library is claimed missing, examine config.log. Both the kernel and each package have a config.log file.