# 7. Using the library

XML/Ada is a library. When compiling an application that uses it, you thus need to specify where the spec files are to be found, as well as where the libraries are installed.

There are several ways to do it:

- The oldest relies on gnatmake. You compile your application with something like:

      gnatmake main.adb -Iprefix/include/xmlada -largs -Lprefix/lib \\
        -lxmlada_input_sources -lxmlada_sax -lxmlada_unicode -lxmlada_dom

- The preferred method, however, is to use the GNAT project files. See the GNAT user’s guide for more information on the project files and how to create them for your application.

  Basically, a project file contains the description of your build environment (source directories, object directories, libraries,...).

  The very simple case is when you have all your sources in the same directory (say `src/`), and the object files are all generated in the `obj/` directory.

  In this case, your project file would look like:

      with "xmlada";
      project Default is
         for Source_Dirs use ("src/");
         for Object_Dir use "obj/";
      end Default;

  and you build your application with:

      gprbuild -Pdefault main.adb

  Note in the project file the first line, which indicates that your application requires XML/Ada to build. This will automatically set the appropriate compiler and linker switches to use XML/Ada. Your application will be linker against all modules of XML/Ada (DOM, SAX, ...).

  If your application doesn’t use DOM, you can replace the first line with something like:

      with "xmlada_sax";

  which will reduce the number of libraries that your application is linked with.

  WHen you are using project files, you need to let GNAT know where to find the project files. This is done by setting the ADA_PROJECT_PATH environment variable, by adding to it the installation directory of XML/Ada, ie the one that contains xmlada.gpr

  If the installation prefix is the same as your GNAT installation, and you are using GNAT more recent than 5.03a, then it will automatically find XML/Ada’s project files.

  Check the `dom/test` directory in the XML/Ada package, which contains both code examples and project files that you can use as a basic for your own code.

The default type of library depends on the way you installed XML/Ada. In all cases, and assuming you installed both static and shared libraries, you can choose among the two by setting the environment variable:

    LIBRARY_TYPE=static

or:

    LIBRARY_TYPE=relocatable

Whatever method you used to build your application, you might have to change, at least one UNIX systems, the environment variable LD_LIBRARY_PATH so that it contains the `lib/` directory in the XML/Ada installation, so that the dynamic libraries are correctly found.

This is not needed if you build XML/Ada as a static directory.

## 7.1. Running on VxWorks

On VxWorks, XML Ada processing might require more stack space than what is typically available from the VxWorks shell, the tasks spawned from there with “sp”, or Ada tasks with no or a too small Storage_Size value attached.

Such stack overflow conditions are typically characterized by non-deterministic erratic behavior and can be cured by allocating more stack space for the tasks involved.