Cross Compile for Android and issues with PyExc_OSError

[GRRedWings]

Bug report

Bug description:

In trying to run Python 3.12 on Android. I have been cross-compiling Python for a number of years. Having built a 64bit version I am getting the following error when I try to run

I get the following error at runtime.
ImportError('dlopen failed: cannot locate symbol "PyExc_OSError" referenced by "/data/data/com.myapp/files/Python64/lib-dynload/_socket.cpython-312.so"...')

I have verified that the _socket.cpython-3.12.so exists. I'm not really sure what other info would be beneficial for people to help me understand this error so I will start with this and happily add more details if requested.

CPython versions tested on:

3.12

Operating systems tested on:

Other

Linked PRs

• gh-111225: Link extension modules against libpython on Android #115780

[GRRedWings]

I'm not sure if this is useful, but I did find this in the Android NDK 26 notes

Issue 360: thread_local variables with non-trivial destructors will cause segfaults if the containing library is dlcloseed. This was fixed in API 28, but code running on devices older than API 28 will need a workaround. The simplest fix is to stop calling dlclose. If you absolutely must continue calling dlclose, see the following table:

[mhsmith]

Issue 360: thread_local variables with non-trivial destructors will cause segfaults if the containing library is dlcloseed

That doesn't seem relevant, because you're not seeing a segfault.

More likely, _socket.cpython-3.12.so has not been linked against libpython3.12.so. You can check this using readelf -d.

[erlend-aasland]

@mhsmith, based on your comment, can we close this issue as not-planned?

[GRRedWings]

Here is the output I got from the readelf command. I'm not exactly sure how to read it, I do not see libpython3.12.so in there though, is this something I can change to link against it?

[mhsmith]

I've just remembered, I also encountered this problem when building Python 3.12 for Chaquopy. I was able to fix it with this patch, which I'll turn into a pull request in the near future.

[GRRedWings]

@mhsmith - Thanks for the update. I have tried your patch as is. Something is still different because it's looking for python3.12.so instead of libpython3.12.so.

I'm playing with your patch file, I'm not an expert but looking at it and trying to figure out what my build needs for some of your changes.

/android-ndk-r26b/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android26-clang -shared -L/python3-android/src/Python-3.12.1/Android/sysroot/usr/lib -pie Modules/arraymodule.o -lpython3.12 -o Modules/array.cpython-312.so
clang-17: warning: argument unused during compilation: '-pie' [-Wunused-command-line-argument]
ld.lld: error: unable to find library -lpython3.12

[mhsmith]

It doesn't say it's looking for python3.12.so, it says it's looking for -lpython3.12, which on Android, just like Linux, should be transformed into libpython3.12.so.

The issue is probably that this file doesn't exist in any of the -L directories on your command line. In particular, I see that the command line doesn't contain -L., even though that should have been assigned to BLDLIBRARY here when ac_sys_system=Linux-android:

cpython/configure

Lines 7500 to 7502 in 2305ca5

	Linux*|GNU*|NetBSD*|FreeBSD*|DragonFly*|OpenBSD*|VxWorks*)
	LDLIBRARY='libpython$(LDVERSION).so'
	BLDLIBRARY='-L. -lpython$(LDVERSION)'

Are you sure you applied the whole patch?

[GRRedWings]

I am pretty confident that I applied the entire patch. What I'm not sure is how I can tell if ac_sys_system is being set right. Is there a log or anything I could put into the configure? I tried using an echo and a printf, but not having any luck.

[GRRedWings]

In looking at this more, and doing a before and after, I can see that it is trying to apply the patch, I don't see errors, but the configure patch is not being applied. I will look into this and make sure the patch is being applied. Sorry about that.

[mhsmith]

I haven't looked at your build process, but maybe you're regenerating the configure script from the configure.ac file after applying the patch.