Enable libffi support for python recipes

Seems that the ctypes module cannot be build against the python3's included sources for libffi, so here we solve the problem by linking with our recipe for libffi. Should be mentioned that the current test app for python3 has been modified by adding libffi to the requirements because the ui for the app has some button to test the ctypes module and also has been documented the issue mentioned.

Author: opacam

doc/source/buildoptions.rst

@@ -17,6 +17,11 @@ This option builds Python 2.7.2 for your selected Android
 architecture. There are no special requirements, all the building is
 done locally.
 
+.. note:: if you add libffi to your requirements, ctypes will be linked to it
+          instead of building the included one in python2 sources. This may be
+          a good idea, because the libffi included in python sources is an old
+          version of libffi and may have some security issues.
+
 
 python3
 ~~~~~~~
@@ -27,6 +32,10 @@ and works with any recent version of the Android NDK.
 Select Python 3 by adding it to your requirements,
 e.g. ``--requirements=python3``.
 
+.. note:: ctypes is not included automatically, if you would like to use it
+          then add libffi to your requirements,
+          e.g. ``--requirements=kivy,libffi,python3``.
+
 
 CrystaX python3
 ###############

pythonforandroid/bootstraps/sdl2/build/src/main/java/org/kivy/android/PythonUtil.java

@@ -37,6 +37,7 @@ protected static ArrayList<String> getLibraries(File filesDir) {
         ArrayList<String> libsList = new ArrayList<String>();
         addLibraryIfExists(libsList, "crystax", libsDir);
         addLibraryIfExists(libsList, "sqlite3", libsDir);
+        addLibraryIfExists(libsList, "ffi", libsDir);
         libsList.add("SDL2");
         libsList.add("SDL2_image");
         libsList.add("SDL2_mixer");

pythonforandroid/python.py

@@ -162,7 +162,7 @@ class GuestPythonRecipe(TargetPythonRecipe):
     '''The file extensions from site packages dir that we don't want to be
     included in our python bundle.'''
 
-    opt_depends = ['sqlite3']
+    opt_depends = ['sqlite3', 'libffi']
     '''The optional libraries which we would like to get our python linked'''
 
     def __init__(self, *args, **kwargs):
@@ -173,11 +173,23 @@ def set_libs_flags(self, env, arch):
         '''Takes care to properly link libraries with python depending on our
         requirements and the attribute :attr:`opt_depends`.
         '''
+        def add_flags(include_flags, link_flags):
+            env['CPPFLAGS'] = env.get('CPPFLAGS', '') + include_flags
+            env['LDFLAGS'] = env.get('LDFLAGS', '') + link_flags
+
         if 'sqlite3' in self.ctx.recipe_build_order:
             info('Activating flags for sqlite3')
             recipe = Recipe.get_recipe('sqlite3', self.ctx)
-            env['CPPFLAGS'] = env.get('CPPFLAGS', '') + recipe.get_build_dir(arch.arch)
-            env['LDFLAGS'] = env.get('LDFLAGS', '') + recipe.get_lib_dir(arch) + ' -lsqlite3'
+            add_flags(' -I' + recipe.get_build_dir(arch.arch),
+                      ' -L' + recipe.get_lib_dir(arch) + ' -lsqlite3')
+
+        if 'libffi' in self.ctx.recipe_build_order:
+            info('Activating flags for libffi')
+            recipe = Recipe.get_recipe('libffi', self.ctx)
+            add_flags(' -I' + ' -I'.join(recipe.get_include_dirs(arch)),
+                      ' -L' + join(recipe.get_build_dir(arch.arch),
+                                   recipe.get_host(arch), '.libs') + ' -lffi')
+
         return env
 
     def get_recipe_env(self, arch=None, with_flags_in_cc=True):

pythonforandroid/recipes/python3/__init__.py

@@ -5,7 +5,11 @@ class Python3Recipe(GuestPythonRecipe):
     '''
     The python3's recipe.
 
-    .. note:: This recipe can be built only against API 21+
+    .. note:: This recipe can be built only against API 21+. Also, in order to
+        build certain python modules, we need to add some extra recipes to our
+        build requirements:
+
+            - ctypes: you must add the recipe for ``libffi``.
 
     .. warning:: The support for libraries is temporary disabled. It will be
         enabled in a near future.

testapps/setup_testapp_python3.py

@@ -2,7 +2,7 @@
 from distutils.core import setup
 from setuptools import find_packages
 
-options = {'apk': {'requirements': 'numpy,sdl2,pyjnius,kivy,python3',
+options = {'apk': {'requirements': 'libffi,numpy,sdl2,pyjnius,kivy,python3',
                    'android-api': 27,
                    'ndk-api': 21,
                    'dist-name': 'bdisttest_python3_googlendk',