Waf

Like SCons, Waf is a general-purpose build system that does not rely on Makefiles to build software.

Phases

The WafBuilder and WafPackage base classes come with the following phases:

configure - configure the project
build - build the project
install - install the project

By default, these phases run:

$ python waf configure --prefix=/path/to/installation/prefix
$ python waf build
$ python waf install

Each of these are standard Waf commands and can be found by running:

$ python waf --help

Each phase provides a <phase> function that runs:

$ python waf -j<jobs> <phase>

where <jobs> is the number of parallel jobs to build with. Each phase also has a <phase_args> function that can pass arguments to this call. All of these functions are empty. The configure phase automatically adds --prefix=/path/to/installation/prefix, so you don’t need to add that in the configure_args.

Testing

WafPackage also provides test and installtest methods, which are run after the build and install phases, respectively. By default, these phases do nothing, but you can override them to run package-specific unit tests.

def installtest(self):
    with working_dir("test"):
        pytest = which("py.test")
        pytest()

Important files

Each Waf package comes with a custom waf build script, written in Python. This script contains instructions to build the project.

The package also comes with a wscript file. This file is used to override the default configure, build, and install phases to customize the Waf project. It also allows developers to override the default ./waf --help message. Check this file to find useful information about dependencies and the minimum versions that are supported.

Build system dependencies

WafPackage does not require waf to build. waf is only needed to create the ./waf script. Since ./waf is a Python script, Python is needed to build the project. WafPackage adds the following dependency automatically:

depends_on("python@2.5:", type="build")

Waf only supports Python 2.5 and up.

Passing arguments to waf

As previously mentioned, each phase comes with a <phase_args> function that can be used to pass arguments to that particular phase. For example, if you need to pass arguments to the build phase, you can use:

def build_args(self, spec, prefix):
    args = []

    if self.run_tests:
        args.append("--test")

    return args

A list of valid options can be found by running ./waf --help.

External documentation

For more information on the Waf build system, see: https://waf.io/book/