I have made a modification to bluedroid code.
My code needs to use the usual semaphore.h which is located at: <aosp_root>/prebuilts/ndk/current/platforms/<platform>/<arch>/usr/include/semaphore.h
Now, in AOSP 6.0+, bluedroid resides in <aosp_root>/system/bt/
In there, there is a header at: <aosp_root>system/bt/osi/include/semaphore.h
In usual AOSP build, if I leave a simple #include <semaphore.h> in my code, the osi header gets included, which is incompatible. Is there a way to modify the build system so that ndk's header gets used for my code?
I'd happily include from this relative path in my code, but <arch> (and probably <platform> ) is/are compile time variables, and should not be hardcoded. workarround for this is also welcomed as alternate answer.
I found that either I need to give fixed paths to correct header in my code, or -
Since I was modifying bluedroid code anyway, I went ahead and modified bluedroid's semaphore.h too. This line in rouge semaphore.h helps:
#include_next "semaphore.h"
gcc extensions FTW. This should continue working till android ndk keeps using gcc..
I know about the general warning that goes with it. Short of writing my own separate semaphore wrapper library based on correct semaphores, this was the only way I could find.
Another alternate I considered was to rename bluedroid's semaphore.h but that will become a maintenance nightmare.