Waf

Using waf to build Samba

As of March 2010, the waf build of Samba4 is now nearly complete. We have waf build rules for libreplace, talloc, tdb, tevent, ldb and Samba4. Kai is working on the waf build for Samba3.

The waf builds are set up so builds appear in bin/ (so if building in source4/lib/ldb then you get source4/lib/ldb/bin/ldbadd for example). This is consistent with the current workflow we use in Samba development.

Where supported, rpath is used so the binaries can be run directly without the need for LD_LIBRARY_PATH. If rpath is not supported then LD_LIBRARY_PATH is automatically set for running the testsuites.

All built files (object, libs, binaries) are in bin. The source tree is never modified (with one minor exception for gen_ndr, as described below). If you do "rm -rf bin" then you're back to a pristine tree.

waf is certainly fast. It uses full content hashing for dependencies, but still manages to run quickly. It also has a 'wafcache' which is a ccache like system, but that applies to all builds, so it will safely cache pidl, asn1, libraries, configure checks etc.

Getting the code

You need to do a git checkout of the waf-wip branch like this:

git clone git://git.samba.org/tridge/samba.git samba-waf
cd samba-waf
git checkout -b waf-wip origin/waf-wip

To update your checkout when something has changed, run this:

cd samba-waf
git pull --rebase

Trying it out

There are two ways to use the waf build. You can use ./autogen-waf.sh followed by ./configure and make as usual, or you can directly call waf.

If you directly call waf then you get some nice additional features, such as a progress bar with 'waf -p' and the ability to specify which tests to run in the testsuite. To run waf directly do this:

• setup your PATH to point at the buildtools/ directory in the root of the Samba sources

export PATH=$HOME/samba-waf/buildtools:$PATH

• don't install waf on your system, instead use the one in

 buildtools/. This ensures we are all always using the same version.

• now try one of the trees that have been converted to waf. For

 example, to try the tdb tree do this:

cd lib/tdb
waf configure --enable-developer --prefix=$HOME/testprefix
waf -p

• that will configure tdb and build the binaries in lib/tdb/bin/. To install them use:

waf install

• The other trees that have been converted are lib/replace,

 lib/talloc, lib/tevent and source4/lib/ldb and source4

Building Samba4

The current waf-wip branch can build Samba4. This is still a work in progress, but if you want to try it, then try this:

cd samba-waf/source4
./autogen-waf.sh
./configure.developer
make
make quicktest

This avoids waf commands directly. To get the most out of waf you should use waf itself instead. Have a look at the configure script and Makefile that autogen-waf.sh produces to see examples of how to use it.

Other commands

Try "waf --help" for help on using waf. Try "waf configure --help" for the equivalent of "./configure --help". I haven't added all of our Samba configuration options yet, but I've put in a few (such as --enable-developer). See lib/replace/wscript for how these are added.

You may also find "waf -v" useful for seeing the build commands. Or use "waf -v clean build" to clean and build a tree, with the commands shown. Use "waf -p" to show a progress bar on the build.

This command illustrates the use of multiple build directories:

waf configure --enable-developer -b devbuild

It ends up creating the binaries in devbuild instead of the default of bin/.

If you want to debug why something isn't working, then you can either increase the verbosity of waf with something like "waf -vvv", or you can enable tracing of a particular phase of the build. For example, you could trace the build dependencies like this:

 waf -v --zone=deps

It is sometimes useful to disable the wafcache when debugging. use the --nocache option for that:

 waf -v --nocache clean build

How it works

Each project within Samba (tdb, ldb, talloc etc) gets a wscript file. That file can depend on other project wscript files. I've kept the wscript files for each project simple by using a 'waf tool' called 'wafsamba', which is in buildtools/wafsamba. Wafsamba is an add-on for waf that sets up the waf configuration and build commands to follow the same sorts of conventions that we have in the existing Samba4 build system.

If you want to have a look at how this was done, then look in buildtools/wafsamba/. You will notice that I've put a lot of paranoia checking in there, as I've found that the exiting config.mk files for the bulk of Samba4 contain some 'interesting' features, such as dependency loops and missing dependencies.

The waf build rules are very simple, and easy to modify. For example:

• the rules for building tdb are here lib/tdb/wscript
• the rules for ldb are here source4/lib/ldb/wscript
• the rules for libreplace, which include most of our configure checks, are here lib/replace/wscript
• the 'wafsamba' waf tool which allows us to describe samba build rules succinctly are here buildtools/wafsamba/wafsamba.py

Adding new commands

In Samba we are used to a number of non-standard make targets, such as 'make quicktest'. We can add the same targets using waf. Even better, when you add a new target in waf it shows up in 'waf --help'.

Main commands (example: ./waf build -j4)
 clean    : removes the build files
 configure: configures the project
 dist     : makes a tarball for redistributing the sources
 distcheck: checks if the sources compile (tarball from 'dist')
 distclean: removes the build directory
 install  : installs the build files
 quicktest: Run the quick test suite
 test     : Run the full test suite
 uninstall: removes the installed files

The commands themselves are arbitrary python. See the source4/selftest directory for some examples on how this works.

Documentation

waf itself is documented in a online book here: http://freehackers.org/~tnagy/wafbook/single.html

The build rules I've added for Samba would also need to be documented if we adopt waf, probably by using the python documentation tools on the wafsamba tool.

Parallel builds

One nice thing about the use of waf is we gain parallel builds. On a 16 CPU machine a complete clean Samba4 build takes just 35s, including rebuilding all of the IDL files. It takes over 5 minutes on the same machine with the old build system.

Here is a graph of the build time versus -j flag

TODO

A short list of work items, not complete!

make waf builds works from subdirectories

You could be able to "cd source4/client" and run waf

reliable builds

we need to detect changing system headers/libraries and give an error.

we should include system headers in the dependecy calculation.

Note that this TODO is well beyond what the current build system can do. We're aiming for a very high standard of dependency checking.

implement LIBRARY->LIBRARY dependency reduction

We want object files used in common between libraries that depend on each other to be removed from the parent library, unless the parent library exports the symbols publicly and the child library is a private library

COMPLETED TODO ITEMS

speedup null build

the null build now takes about 1.6s which is good enough

fix 'waf test'

all s4 tests now pass with the waf build

check each compiler option

for options like --enable-developer we need to check the compiler supports the various options.

The flags should only be used in the build and not within configure checks.

get the waf build working in the build farm

This will test the portability quite well

its passing on some hosts in the build farm. The others are being worked on

get git revision in logs and -V output

bin/samba -V should show the git revsion

waf configure --help

waf configure --help should display 'build' as possible command

implement waf install

We need to call the same install scripts we used from the old build, at least initially.

all done now

add --no-bundled-libraries

done, as --bundled-libraries=LIST