The top level Makefile will automatically build all libraries placed in
directories of the form lib.+ and then all programs in subdirectories of the
programs directory.  In order for this to work correctly, certain files and make
targets are required.

    Each library must provide Make.header and Make.files in its top level
directory.  The first target in Make.header must be "default," and must build
the static and/or shared versions of the library.  If J_BUILD_SHARED_LIB is not
defined, only the static version is built. If J_NEED_SEPARATE_O_FILES is
defined, only the shared version is built.  Otherwise, both versions are built.
If the install is done as root, "default" should copy the resulting libraries to
the ${JX_LIB_ROOT}/ directory, and the "jxuninstall" target should remove the
libraries from this directory.  Because "default" is so complicated, it is
implemented for you in the file include/make/default_lib_target.  Refer to
libjcore/Make.header and libjx/Make.header for examples of how to use this file.

    Make.header must also provide the target "Makefiles" to build the Makefiles
in any subdirectories.  (e.g. the Makefile for the test suite)  Make.header
should also define "tidy" and "clean" as double colon targets to clean up any
subdirectories.  (e.g. the test suite)  The source distribution should also
include a symbolic link placed in the include directory that points to the
library's header files and symbolic links placed in the lib directory that point
to the static and shared versions of the library in the library's top level
directory.  The JTree library provides an example of how to do all this.

    Each library must also provide a *_constants file in include/make/.  This
defines version numbers, shortcuts, and augments J_STRING_FILES to include all
string database files that are required by the library.  All program Make.header
files include these *_constants files.  jtree_constants provides an example of
how to do this.

    Each program must provide Make.header and Make.files in its top level
directory.  In this case, Make.header must provide the target "Makefiles" to
build the Makefiles in any subdirectories, the target "jxinstall" to build the
program, strip it, and place it in ${JX_INSTALL_ROOT}/, and the target
"jxuninstall" to remove the program from this directory.  For the user's
convenience, the first target in Make.header should be "default," and should
build first the required libraries and then the program.  It is also helpful to
provide a target "static" to build a statically linked version of the binary.
In order to make it easy for others to build binary distributions for other
platforms, Make.header should also define the targets "shared" and "link" to
build the tar files containing the dynamically linked executable and link-kit,
respectively.  If there are any subdirectories with their own Makefiles,
Make.header should define "tidy" and "clean" as double colon targets to clean up
these subdirectories.  Code Crusader provides an example of how to do all this.

    While studying the example Make.header files, you will notice that they
include the files include/make/jx_constants and include/make/jx_config.
jx_constants defines system independent constants needed for the various
required targets, such as J_DISTR_TAR_DIR which is discussed below.  It also
defines the variables ljcore and ljx which expand to the appropriate -l
arguments for use in the make variable LOADLIBES.  jx_constants requires that
JX_ROOT be defined before it is included.  jx_config defines system dependent
constants.  Of particular interest are J_BUILD_SHARED_LIB and
J_NEED_SEPARATE_O_FILES which should be used in the Make.header for every
library, as discussed above.

    For the user's convenience and to insure that incompatible versions never
get linked together, all libraries and programs should be packaged from above
the main JX directory, defined in the variable J_DISTR_TAR_DIR.  This way, the
user can download the source to all the libraries and programs, unpack all the
tar files in the same directory, and then build them all with a single make
command.