CODEWITHSUNDEEP
androidpythonandroid-ndkkivy
Kuldeep Dhaka
Kuldeep Dhaka

Reputation: 553

android nkd and sdk compatibility issue (run time linker error)

Should/does NDK9 work with android API19? (though it was released with API18).

Full story:

I was building an Android App using kivy, python-for-android and buildozer.

compiling with MDK9 (ie 9d) and api19 result in error:

E/AndroidRuntime( 1773): java.lang.UnsatisfiedLinkError: Cannot load library: soinfo_relocate(linker.cpp:975): cannot locate symbol "wait4" referenced by "libpython2.7.so"...

compiling with NDK9 (ie 9d) and API18 works. :)

Upvotes: 2

Views: 718

Answers (2)

reactive-core
reactive-core

Reputation: 1081

Just in case anyone stumbles across this. I had the same issue, but building python from scratch using the platform tools, and with NDK r10 and r10b.

It's because google removed an inline wait4() declaration in the NDK platform android-19. The original problem was that wait4() was exposed in the headers but not declared anywhere, so if you tried to use wait4 on older NDKs, you'd probably crash (like you do now).

So they went in and added it to libc.so in API 18 I believe, but libc.so is shipped with the O/S, so devices with O/S older than 18 would not have wait4, so they patched it by adding an inlined wait4() method in NDK platforms up through android-18, then took it out in android-19 I'm not fully sure why yet, seems like it could have made more sense to leave it alone at that point, especially since it's considered an obsolete function. I was told I should not build against android-19 if I wanted the app to run on devices older than API 18, but others say to always use the latest NDK to match your build target. Here is a link to the problem.

https://code.google.com/p/android/issues/detail?id=19854

In my case, I went into the cpython Modules/posixmodule.c file, and added:

#if defined(__ANDROID__)
#undef HAVE_WAIT4
#endif

And in my case that's fine, because none of my python modules use wait4. Indeed, Linux deems the wait4 command obsolete (http://linux.die.net/man/2/wait4). You should instead use the waitpid.

So, even if you download some 3rd party python module that does use wait4, you have 2 options. 1) change that module to use waitpid, or 2) update the Modules/posixmodule.c file inside the "ifdef HAVE_WAIT4" section, and replace the wait4 call with waitpid. The downside is you lose the returned resource usage information, which waitpid doesn't provide, so then if your module needs that, you'd have to add something to retrieve resource usage for that pid separately.

Alternatively, you could remove "wait4" from your configure script if you never plan to use it, and any modules you add that needed it would break, at which point the new engineer working on the problem would have to rediscover all of this over again.

Upvotes: 3

tito
tito

Reputation: 13271

Android SDK are released more often that NDK. It happened more than once that if you use a too recent SDK, the NDK will not have the .h for it. Now i'm not sure this would be related to your issue at all.

Upvotes: 0

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