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Using a Library through the External Package Mechanism

note, this section is still in progress

What if you want to make an external library available to all the packages in your release? It would be tedious to modify each new package you develop as in the section above. A better solution is to create an external package that interfaces to your library. In your release directory, do the following:

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This SConscript calls the funciton standardSConscript(), but this is not what we want. We want to use standardExternalPackage(). Change the file to look like:

# Do not delete following line, it must be present in 
# SConscript file for any SIT project
Import('*')
import os
from os.path import join as pjoin
from SConsTools.standardExternalPackage import standardExternalPackage
#
# For the standard external packages which contain includes, libraries, 
# and applications it is usually sufficient to call standardExternalPackage()
# giving some or all parameters.
#
PREFIX = os.path.expanduser('~username/mycode')
INCDIR = "include"
LIBDIR = "lib"
PKGLIBS = "mylib"
standardExternalPackage('MyCode', **locals())

After doing scons, any package in the release will be able to call functions in mycode by doing

#include "MyCode/myheader.h"

The build system will identify the dependency on the MyCode package. Given the PKGLIBS parameter, it will then add mylib to the link line. libmylib.so will be found because PREFIX and LIBDIR together give the directory where the MyCode shared object libraries are. This directory is not added to the LD_LOAD_LIBRARY path or explicitly used when building. By default, standardExternalPackage() will make soft links from the $SIT_ARCH/lib directory of your release to all the shared object libraries in the external package lib directory. When you ran sit_setup from your release directory, it placed the $SIT_ARCH/lib directory of your release first in the $LD_LIBRARY path. This is the mechanism by which MyCode libraries are made available to all packages in your release.

The above SConscript file for an external package is the simplest case. MyCode has a common directory structure: a base directory with an include and lib directory as sub-directories. Thus the PREFIX, INCDIR and LIBDIR parameters work well to describe it to SConsTools. If the include and lib directory were in different places, one could omit the PREFIX parameter and give absolute paths for INCDIR and LIBDIR:

INCDIR = os.path.expanduser('~username/mycode/include')
LIBDIR = os.path.expanduser('~username/mycode/lib')

It the external package has stand alone programs or tools to run, you can add the BINDIR parameter.  If MyCode were to in turn depend on another external package, that package could be defined in the same SConScript file and the DEPS parameter could be used when defining MyCode with standardExternalPackage.. An example of using these options can be seen in SConscript file for the hdf5 package. One can do

addpkg hdf5

Within your release and take a look at hdf5/SConscript.

Building Part of the Release

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