Fix librt recipe requires that NDK folder is writable

pythonforandroid/archs.py

@@ -1,8 +1,9 @@
-from os.path import (exists, join, dirname, split)
+from distutils.spawn import find_executable
 from os import environ, uname
+from os.path import (exists, join, dirname, split)
 from glob import glob
+import shlex
 import sys
-from distutils.spawn import find_executable
 
 from pythonforandroid.recipe import Recipe
 from pythonforandroid.util import BuildInterruptingException, build_platform
@@ -20,6 +21,12 @@ def __init__(self, ctx):
         super(Arch, self).__init__()
         self.ctx = ctx
 
+        # Allows injecting additional linker paths used by any recipe.
+        # This can also be modified by recipes (like the librt recipe)
+        # to make sure that some sort of global resource is available &
+        # linked for all others.
+        self.extra_global_link_paths = []
+
     def __str__(self):
         return self.arch
 
@@ -56,7 +63,13 @@ def get_env(self, with_flags_in_cc=True, clang=False):
             cflags.append('-gcc-toolchain {}'.format(toolchain))
 
         env['CFLAGS'] = ' '.join(cflags)
-        env['LDFLAGS'] = ' '
+
+        # Link the extra global link paths first before anything else
+        # (such that overriding system libraries with them is possible)
+        env['LDFLAGS'] = ' ' + " ".join([
+            "-L" + shlex.quote(l)
+            for l in self.extra_global_link_paths
+        ]) + ' '
 
         sysroot = join(self.ctx._ndk_dir, 'sysroot')
         if exists(sysroot):

pythonforandroid/recipes/librt/__init__.py

@@ -1,5 +1,7 @@
+from os import makedirs, remove
+from os.path import exists, join
 import sh
-from os.path import join
+
 from pythonforandroid.recipe import Recipe
 from pythonforandroid.logger import shprint
 
@@ -20,17 +22,34 @@ class LibRt(Recipe):
     def libc_path(self):
         return join(self.ctx.ndk_platform, 'usr', 'lib', 'libc')
 
-    @property
-    def librt_path(self):
-        return join(self.ctx.ndk_platform, 'usr', 'lib', 'librt')
-
     def build_arch(self, arch):
-        shprint(sh.ln, '-sf', self.libc_path + '.so', self.librt_path + '.so')
-        shprint(sh.ln, '-sf', self.libc_path + '.a', self.librt_path + '.a')
-
-    def postbuild_arch(self, arch):
-        shprint(sh.rm, self.librt_path + '.so')
-        shprint(sh.rm, self.librt_path + '.a')
+        # Create a temporary folder to add to link path with a fake librt.so:
+        fake_librt_temp_folder = join(
+            self.get_build_dir(arch.arch),
+            "p4a-librt-recipe-tempdir"
+        )
+        if not exists(fake_librt_temp_folder):
+            makedirs(fake_librt_temp_folder)
+
+        # Set symlinks, and make sure to update them on every build run:
+        if exists(join(fake_librt_temp_folder, "librt.so")):
+            remove(join(fake_librt_temp_folder, "librt.so"))
+        shprint(sh.ln, '-sf',
+                self.libc_path + '.so',
+                join(fake_librt_temp_folder, "librt.so"),
+                )
+        if exists(join(fake_librt_temp_folder, "librt.a")):
+            remove(join(fake_librt_temp_folder, "librt.a"))
+        shprint(sh.ln, '-sf',
+                self.libc_path + '.a',
+                join(fake_librt_temp_folder, "librt.a"),
+               )
+
+        # Add folder as -L link option for all recipes if not done yet:
+        if fake_librt_temp_folder not in arch.extra_global_link_paths:
+            arch.extra_global_link_paths.append(
+                fake_librt_temp_folder
+            )
 
 
 recipe = LibRt()