How to substitute dlopen in Android N?

[Andreas Falkenhahn]

I have an NDK app which can be extended via plugins which are loaded via dlopen.
This used to work fine but it no longer works with Android N. As stated in the
7.0 release notes, dlopen support is now officially abandoned. (see here:
https://developer.android.com/about/versions/nougat/android-7.0-changes.html#ndk )

That's why I need to change my plugin design into something that is officially
supported and is future-proof. The most obvious choice would be to use
Android's Service API and simply distribute my plugins as separate APKs that
implement a Service.

However, I don't really like that idea since I'm using the NDK and I don't think
that the Service API is available for the NDK. Of course, I could create a Service
in Java and then use JNI to integrate it with my C code but this is of course not
a very elegant solution.

That's why I'd like to ask what's the recommended way to support plugins which were
previously dlopen-based in Android N? Is there an alternative route or am I forced
to use the Service API now?

--
Best regards,
Andreas Falkenhahn mailto:and...@falkenhahn.com

[Philippe Simons]

It's not stated that dlopen is abandoned / deprecated.

It's stated that using dlopen to access private API is now forbidden...

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[Andreas Falkenhahn]

On 27.01.2017 at 22:32 Philippe Simons wrote:

> It's not stated that dlopen is abandoned / deprecated.
> It's stated that using dlopen to access private API is now forbidden...

Well, yeah, that's what I meant of course. On Android N I'm no longer able to
dlopen() non-system shared objects. That's why I'm wondering how I should
solve this problem...

[Dan Albert]

On Android N I'm no longer able to
dlopen() non-system shared objects. That's why I'm wondering how I should
solve this problem...

As in you can't dlopen something within your app? 

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[J Decker]

On Fri, Jan 27, 2017 at 3:08 PM, 'Dan Albert' via android-ndk <andro...@googlegroups.com> wrote:

On Android N I'm no longer able to
dlopen() non-system shared objects. That's why I'm wondering how I should
solve this problem...

As in you can't dlopen something within your app? 

Should be just that you can't open in other's apps (like installing a common shared openCV library that others link to) and system libraries that aren't meant to be linked to.

On Fri, Jan 27, 2017 at 2:41 PM, Andreas Falkenhahn <and...@falkenhahn.com> wrote:

On 27.01.2017 at 22:32 Philippe Simons wrote:

> It's not stated that dlopen is abandoned / deprecated.
> It's stated that using dlopen to access private API is now forbidden...

Well, yeah, that's what I meant of course. On Android N I'm no longer able to
dlopen() non-system shared objects. That's why I'm wondering how I should
solve this problem...

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Best regards,
 Andreas Falkenhahn                            mailto:and...@falkenhahn.com

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[J Decker]

On Fri, Jan 27, 2017 at 8:32 PM, J Decker <d3c...@gmail.com> wrote:

On Fri, Jan 27, 2017 at 3:08 PM, 'Dan Albert' via android-ndk <andro...@googlegroups.com> wrote:

On Android N I'm no longer able to
dlopen() non-system shared objects. That's why I'm wondering how I should
solve this problem...

As in you can't dlopen something within your app? 

Should be just that you can't open in other's apps (like installing a common shared openCV library that others link to) and system libraries that aren't meant to be linked to.

And maybe in data space; which makes 'download a plugin to add functionality' kinda improbable. 

[Andreas Falkenhahn]

On 28.01.2017 at 00:08 'Dan Albert' via android-ndk wrote:

> As in you can't dlopen something within your app?

Oops, sorry, actually, dlopen() is still working fine on Android 7.0. I was getting
the following error message:

Detected problems with app native libraries (please consult log for detail):
foobar.so: text relocations

I thought that this was caused by the new dlopen() policy in Android N but
actually it was caused by a bug in Android NDK r8b which I was still using.
Updating to a newer NDK solved the problem.

Still, I'm wondering what exactly does Google mean when they say that starting
in Android 7.0 "the system prevents apps from dynamically linking against non-NDK
libraries"? To me this sounds like dlopen()'ing non-system libraries is forbidden
now but as I said, it still works so I guess I'm misunderstanding something here?
But what does Google mean by it then?

[Dan Albert]

I guess the wording does technically make it sound like you're now allowed to link to your own libraries. That definitely is not the case. The policy is that your cannot link to or dlopen private system libraries (anything in /system/lib that is not in the NDK).

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[Grégory Pakosz]

On Saturday, January 28, 2017 at 7:18:42 PM UTC+1, Dan Albert wrote:

I guess the wording does technically make it sound like you're now allowed to link to your own libraries. That definitely is not the case. The policy is that your cannot link to or dlopen private system libraries (anything in /system/lib that is not in the NDK).

In that respect, it's about time NDK gives us a way to get a backtrace ;) 

[Dan Albert]

In that respect, it's about time NDK gives us a way to get a backtrace ;) 

That's actually coming very soon! https://android-review.googlesource.com/c/325718/

It's landing in the platform for O, but I plan on shipping it as part of the NDK once we work out any of the kinks.

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