[gentoo-portage-dev] [PATCH v2] setup.py: enable libc bindings optionally (bug 594744)

[Zac Medico]

The libc bindings are optional, since ctypes is used as a fallback when
they are not available. The libc bindings do not support cross-
compilation, therefore it is useful to be able to build them
conditionally. This patch adds an option to enable them conditionally,
which the ebuild can use by adding the following code to the
python_prepare_all function:

    if use native-extensions; then
        printf "[build_ext]\nportage-ext-modules=true" >> \
            setup.cfg || die
    fi

X-Gentoo-Bug: 594744
X-Gentoo-Bug-URL: https://bugs.gentoo.org/594744
---
[PATCH v2] adds a "Native Extensions" section to the README file, and
updates the commit message to note that the libc bindings are optional
because ctypes is used as a fallback.

 .travis.yml |  1 +
 README      | 19 +++++++++++++++++++
 setup.py    | 21 +++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index c098c4d..ded5893 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,6 +10,7 @@ python:
 install: "pip install lxml"
 
 script:
+    - printf "[build_ext]\nportage-ext-modules=true" >> setup.cfg
     - ./setup.py test
     - ./setup.py install --root=/tmp/install-root
     # prevent repoman tests from trying to fetch metadata.xsd
diff --git a/README b/README
index 5e78842..311d036 100644
--- a/README
+++ b/README
@@ -13,6 +13,25 @@ Dependencies
 Python and Bash should be the only hard dependencies. Python 2.7 is the
 minimum supported version.
 
+Native Extensions
+=================
+
+Portage includes some optional native extensions which can be built
+in the source tree by running the following command:
+
+    python setup.py build_ext --inplace --portage-ext-modules
+
+The following setup.cfg settings can be used to enable building of
+native extensions for all invocations of the build_ext command (the
+build_ext command is invoked automatically by other build commands):
+
+   [build_ext]
+   portage-ext-modules=true
+
+Currently, the native extensions only include libc bindings which are
+used to validate LC_CTYPE and LC_COLLATE behavior for EAPI 6. If the
+native extensions have not been built, then portage will use ctypes
+instead.
 
 Licensing and Legalese
 =======================
diff --git a/setup.py b/setup.py
index e900aaa..e2c6b6e 100755
--- a/setup.py
+++ b/setup.py
@@ -6,6 +6,7 @@ from __future__ import print_function
 
 from distutils.core import setup, Command, Extension
 from distutils.command.build import build
+from distutils.command.build_ext import build_ext as _build_ext
 from distutils.command.build_scripts import build_scripts
 from distutils.command.clean import clean
 from distutils.command.install import install
@@ -624,6 +625,25 @@ def get_manpages():
 				yield [os.path.join('$mandir', topdir, 'man%s' % g), mans]
 
 
+class build_ext(_build_ext):
+	user_options = _build_ext.user_options + [
+		('portage-ext-modules', None,
+		 "enable portage's C/C++ extensions (cross-compling is not supported)"),
+	]
+
+	boolean_options = _build_ext.boolean_options + [
+		'portage-ext-modules',
+	]
+
+	def initialize_options(self):
+		_build_ext.initialize_options(self)
+		self.portage_ext_modules = None
+
+	def run(self):
+		if self.portage_ext_modules:
+			_build_ext.run(self)
+
+
 setup(
 	name = 'portage',
 	version = '2.3.1',
@@ -651,6 +671,7 @@ setup(
 
 	cmdclass = {
 		'build': x_build,
+		'build_ext': build_ext,
 		'build_man': build_man,
 		'build_scripts': x_build_scripts,
 		'build_scripts_bin': x_build_scripts_bin,
-- 
2.7.4