Include prebuilt shared library in Android AOSP

Question

I would like to use a prebuilt shared library (let's call it libmylib.so) from some AOSP code, for instance in the folder framework/av/media/libmedia.

Since my target is Nexus 7, I created a new folder device/asus/flo/mylib, where I put 2 files:

• libmylib.so
• Android.mk

My first try was to use PREBUILT_SHARED_LIBRARY in Android.mk as follow:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libmylib
LOCAL_SRC_FILES := libmylib.so
include $(PREBUILT_SHARED_LIBRARY)

Then, I added the dependency in the libmedia module (in framework/av/media/libmedia/Android.mk, I added libmylib to the LOCAL_SHARED_LIBRARIES list).

Unfortunately, the build (lunch aosp_flo-eng && make -j4) failed:

*** No rule to make target `out/target/product/flo/obj/SHARED_LIBRARIES/libmylib_intermediates/export_includes’, needed by `out/target/product/flo/obj/SHARED_LIBRARIES/libmedia_intermediates/import_includes’. Stop.

---

Therefore, I replaced PREBUILT_SHARED_LIBRARY by BUILD_PREBUILT (I don't really understand the difference):

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libmylib
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_SUFFIX := .so
LOCAL_SRC_FILES := libmylib.so
include $(BUILD_PREBUILT)

That way, the build succeeded.

So I flashed the image:

fastboot flashall -w

But unfortunately, the tablet did not boot. adb logcat printed indefinitely:

E SurfaceFlinger: error posting framebuffer: -22
E qdgralloc: fb_post: FBIOPUT_VSCREENINFO for primary failed, str: Invalid argument
E SurfaceFlinger: error posting framebuffer: -22
E qdgralloc: fb_post: FBIOPUT_VSCREENINFO for primary failed, str: Invalid argument
E SurfaceFlinger: error posting framebuffer: -22
E qdgralloc: fb_post: FBIOPUT_VSCREENINFO for primary failed, str: Invalid argument

---

If I remove libmylib from framework/av/media/libmedia/Android.mk, everything is fine, the tablet boots correctly.

Note that I don't even call the library at this point, the simple fact to declare it as a libmedia dependency is problematic.

I tried with several .so (including one that I tested on the tablet with a binary calling a function it exposes, directly in /data/local/tmp, so the .so is ok).

I probably missed something. Any clue?

Answer 1

I tested the same thing on Nexus 5, which is fortunately more verbose :)

The problem was that LOCAL_MODULE and LOCAL_SRC_FILES didn't use the same lib name (a problem that was not present in my original post, since I wanted to abstract the details).

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libmylib
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_SUFFIX := .so
LOCAL_SRC_FILES := libsomething.so
include $(BUILD_PREBUILT)

The module was libmylib, but the source file was libsomething.so.

That way, there was a /system/lib/libsomething.so, but a dlopen() failed because /system/lib/libmylib.so was not found.

Using the same name for both solves the problem:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libsomething
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_SUFFIX := .so
LOCAL_SRC_FILES := libsomething.so
include $(BUILD_PREBUILT)