If you use project files, library installation is part of the library build process (see the ‘Installing a Library with Project Files’ section of the ‘GNAT Project Manager’ chapter of the GPRbuild User’s Guide).
When you’re not able to use project files for some reason, you can
also install the library so that the sources needed to use the library
are on the Ada source path and the ALI files & libraries be on the Ada
Object path (see Search Paths and the Run-Time Library (RTL)),
but we don’t recommend doing this. Alternatively, the system
administrator can place general-purpose libraries in the default
compiler paths, by specifying the libraries’ location in the
configuration files ada_source_path and
ada_object_path. These configuration files must be located in
the GNAT installation tree at the same place as the gcc spec
file. The location of the gcc spec file can be determined as follows:
$ gcc -v
The configuration files mentioned above have a simple format: each line must contain one unique directory name. Those names are added to the corresponding path in their order of appearance in the file. The names can be either absolute or relative; in the latter case, they are relative to where theses files are located.
The files ada_source_path and ada_object_path might not be
present in a
GNAT installation, in which case, GNAT looks for its run-time library in
the directories adainclude (for the sources) and adalib (for the
objects and ALI files). When the files exist, the compiler does not
look in adainclude and adalib, and thus the
ada_source_path file
must contain the location for the GNAT run-time sources (which can simply
be adainclude). In the same way, the ada_object_path file must
contain the location for the GNAT run-time objects (which can simply
be adalib).
You can also specify a new default path to the run-time library at
compilation time with the --RTS=rts-path switch. You can
thus choose the run-time library you want your program to be
compiled with. This switch is recognized by gcc, gnatmake,
gnatbind, gnatls, and all project aware tools.
You can install a library before or after the standard GNAT library by selecting the ordering the lines in the configuration files. In general, a library must be installed before the GNAT library if it redefines any part of it.