Virtually every software development project has some need to integrate with third-party software libraries. In a traditional build system, you might list the include paths, libraries, and library directories right in your Makefile or configuration file for whatever build system you are using. With abuild, the best way to integrate with a third-party library is to use a build item whose sole purpose is to export that library's information using an Abuild.interface file. In the simplest cases, a third-party library build item might be an interface only build item (described above) that just includes the appropriate library directives in a static Abuild.interface file. For example, a build item that provides access to the PCRE (Perl-compatible regular expression) libraries on a Linux distribution that has them installed in the system's standard include path might just include an Abuild.interface with the following contents:

LIBS = pcrecpp pcre

For Java build items, a third-party JAR build item would typically append the path to the JAR file to the abuild.classpath.external interface variable. Sometimes, the process may be more involved. For example, on a UNIX system, it is often desirable to use autoconf to determine what interface is required for a particular library. We present an example of using autoconf with abuild in Section 15.3, “Autoconf Example”. Still other libraries may use pkg-config. For those libraries, it may make sense to create a simple set of build rules that automatically generate an Abuild.interface after-build file (also discussed in Section 15.3, “Autoconf Example”) by running the pkg-config command. ^[10]

Whichever way you do it for a given package, the idea is that you should always create a build item whose job it is to provide the glue between abuild and the third-party library. Other build items that need to use the third-party library can then just declare a dependency on the build item that provides the third-party library's interface. This simplifies the process of using third-party libraries and makes it possible to create a uniform standard for doing so within any specific abuild build tree. It also alleviates the need to duplicate information about the third-party library throughout your source tree.