Dynamically linking against libc++ doesn't work in NDK r14b

[Andreas Falkenhahn]

I'm compiling a shared object using NDK r14b which uses C++11 and I'm linking dynamically against libc++. However, when dlopen()ing this shared object, I get the following error message:

dlopen failed: library "libc++_shared.so" not found

When I statically link against libc++ it's working fine. Isn't dynamically linking against libc++ supported?

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Andreas Falkenhahn mailto:and...@falkenhahn.com

[Ryan Prichard]

Isn't dynamically linking against libc++ supported?

Yes, that is supported.

What version of Android do you see this problem with?

There's a known issue affecting versions older than Android 4.3, documented online:

Shared runtimes

If your app targets a version of Android earlier than Android 4.3 (Android API level 18), and you use the shared library variant of a given C++ runtime, you must load the shared library before any other library that depends on it.

 

Rather than managing this yourself, we recommend using ReLinker.

https://developer.android.com/ndk/guides/cpp-support.html#shared_runtimes

This problem can be fixed by calling loadLibrary() on libc++_shared.so first, then calling it on your app's shared library.

-Ryan

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[Andreas Falkenhahn]

On 26.03.2018 at 22:37 'Ryan Prichard' via android-ndk wrote:

> Yes, that is supported.
> What version of Android do you see this problem with?
> There's a known issue affecting versions older than Android 4.3, documented online:
> Shared runtimes
> If your app targets a version of Android earlier than Android 4.3
> (Android API level 18), and you use the shared library variant of a
> given C++ runtime, you must load the shared library before any other library that depends on it.
>
> Rather than managing this yourself, we recommend using ReLinker.
> https://developer.android.com/ndk/guides/cpp-support.html#shared_runtimes
> This problem can be fixed by calling loadLibrary() on
> libc++_shared.so first, then calling it on your app's shared library.

Weird, I get the error on Android O. But since it works when linking
statically it's not that much of a problem. Still weird, though.

[Ryan Prichard]

The NDK's libc++_shared.so needs to be bundled in an APK's lib/<abi> directories, alongside other shared libraries. Maybe you're not including it?

-Ryan

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[Andreas Falkenhahn]

On 27.03.2018 at 01:01 'Ryan Prichard' via android-ndk wrote:

> The NDK's libc++_shared.so needs to be bundled in an APK's
> lib/<abi> directories, alongside other shared libraries. Maybe you're not including it?

Yes, that was the problem. I didn't know that I had to include
the shared lib in the APK. I thought it would use a one
provided by the system. Works now, thanks.

[Dan Albert]

I thought it would use a one provided by the system.

That's the case for most NDK libraries, but in the case of the C++ stdlib it works out for the best to bundle it with the app. You wouldn't want to be locked out of C++17 just because you're supporting devices from 2016 :)

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[Alexis Barra]

Hey Dan,

I don't understand why this library works in a different way. Could you explain it? or maybe point me a resource to read to understand the reason.

Thanks!

Alexis

[Ray Donnelly]

You do not want there end users device dictating what c++ language specification you can use in your application so you should bundle the ndk DSO with your app. That way the ndk dictates this aspect.

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