BUILD Systems for Samba 4.0 (python-based waf in particular)

[Andrew Bartlett]

(This is the Team's agreed statement explaining the role of the two
build systems in Samba 4.0.  Please, if you have can't use the waf build
system, and so need the autoconf system for 4.0, reply and let us know
your reasons and needs here or in the specific threads I'm raising on
samba-technical). 

Thanks,

Andrew Bartlett


BUILDING SAMBA 4.0
(which build system to use and why)
===================================

The waf build
-------------

Samba 4.0 ships with a new build system, based on waf.  A background to
this build system can be found at https://wiki.samba.org/index.php/Waf

This is the build system that is used when you run ./configure && make
in the top level of a Samba 4.0 release tree.

For the vast majority of our users, this is the build system you should
use.  It supports parallel and incremental builds, and builds the whole
Samba suite, the file server, the print server, the NT4 domain
controller, winbind, the AD Domain Controller, the client libraries and
the python libraries.  

A key feature for many of our distributors and OEMs is that despite the
range of additional features, the resulting binaries and libraries are
substantially smaller, because we use shared libraries extensively. 

For distributions that have a requirement to use the system-supplied
Kerberos library, we support building against a Heimdal or system MIT
Kerberos library, provided the version is recent enough (otherwise we
will use our internal version of Heimdal).  Please note that builds
with MIT krb5 support will not have AD DC features.

By the time of the first release candidate, we will finish renaming
the binaries that we ship so that where we provide a tool under a name
that was used in Samba 3.x, it continues to behave in the same way it
always has.  This will ensure that our change in build system does not
impact on our user's ability to use Samba as they always have.

For developers, this build system backs a comprehensive 'make test',
which provides code coverage of around 48% of our code by line:
https://build.samba.org/lcov/data/coverage/samba_4_0_test/

This build system also implements important features such as ABI
checking (which protects you as users from accidental changes to our
published libraries), symbol versions and dependency checked incremental
rebuilds after header-file changes. 

The waf build also assists developers by providing fully-linked binaries
that run from bin/ without needing to set LD_LIBRARY_PATH. 

For users who do not have python installed on their systems, we provide
a install_with_python.sh script, which will install a local copy of
python sufficient to run the build system, without impacting on the rest
of the system.  

Within this requirement, we expect that this build will run on all our
supported platforms, and will actively deal with any portability issues
that users can bring to our attention. 

For all these reasons, we highly recommend this new build system to all
our users, for whatever purpose you want to put Samba to.

The autoconf build
------------------

For a small number of users, the requirement to have access to Python
2.4 and perl will be unacceptable, and for these users we continue to
provide the 'autoconf' build system used in Samba 3.x under the
source3/.  This will build fewer parts of Samba, but should not be seen
as 'the file server build' (typical file server deployments should use
the top level build), but as a measure provided with limited features
for systems and organisations unable to meet the requirements for the
new build system.

If you do need to use the autoconf build system, please let us know:
both why you cannot use the 'waf' build in the top level, and what
features of the source3 build that you require.  We need this
information to assess the continuing demand for this parallel
infrastructure, and to determine which features need to remain available
in both build systems.

Optional Libraries
------------------

To assist users and distributors to build Samba with the full feature
set, by the first release candidate the build system will abort if our
dependent libraries and their header files are not found on the target
system.  This will mean for example, that xattr, acl and ldap headers
must be installed for the default build to complete.  The configure
system will check for these headers, and the error message will
indicate:
 - the required header and library
 - the option (such as --without-acl-support) that can be specified to
   skip this requirement, and
 - the feature (ACL support optional for file servers, mandatory for AD
   Domain Controller) being skipped. 

This will assist users and in particular distributors in building fully
functional packages, while allowing those on systems truly without these
facilities to continue to build Samba after careful consideration. 

-- 
Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org