[LTP] [PATCH v1] include/mk/env_post.mk: enable __ANDROID__ definition for Android build

[阮正旺]

Hi Steve,


-------- Original Message --------
From: Steve Muckle
Sent: Wed, 24 Apr 2019 12:23:01 -0700
To: Petr Vorel, Zhengwang Ruan
Cc: Sandeep Patil, Ltp, Kernel-team
Subject: Re: [LTP] [PATCH v1] include/mk/env_post.mk: enable __ANDROID__ 
definition for Android build
> Hi Petr, Zhengwang,
>
> On 4/24/19 2:14 AM, Petr Vorel wrote:
>> Hi Steve, Sandeep,
>>
> ...
>>
>> Please, when you have time, can you please have a look into this?
>>
>> IMHO the question is whether code guarded by __ANDROID__ 
>> (lib/tst_kernel.c,
>> rt_tgsigqueueinfo01.c, etc.) works as expected in NDK build (as in 
>> aosp you use
>> definitions in Android.bp anyway).
>>
>> According to [1] -D__ANDROID__ is defined by toolchain (I understand 
>> it by both
>> aosp build and builds using NDK), so it shouldn't be needed.
>
> Using Sandeep's instructions and with your latest merged fixes I was 
> able to build unmodified upstream with the NDK. I just tried running 
> one of the test binaries on my device to sanity check it.
>
> I put in an #error if __ANDROID__ is defined and it does look to be 
> set by the NDK compiler. FWIW I am using Android API level 26, the 
> minimum which provides hasmntopt. This gets configured in the "Set up 
> ndk toolchains for autoconf" step Sandeep mentioned by setting the CC 
> and CXX env vars appropriately.
>
> Zhengwang can you try the steps Sandeep mentioned (with the API level 
> tweak I mentioned above)?

Yes, I tried the steps as Sandeep mentioned and also put an "#error" if 
__ANDROID__ was defined, it proves NDK has defined it.

Thanks you guys very much for letting me know this.  :-)


>
>> Not sure if it makes sense to build for android with non android 
>> toolchain (i.e.
>> no aosp nor NDK, use generic arm cross compile toolchain or standard 
>> gcc/clang
>> in case of intel platform). If yes, than this patch would be useful, 
>> as generic
>> toolchain obviously don't define __ANDROID__.
>
> Zhengwang had said
>
> >  In the case of cross-compilation, I think it still makes sense, since
> > we can use the same toolchain, such as clang,  and build parameters
> > (the specify the include headers and libs, etc) as AOSP.
>
> but it's not clear to me since you need to have bionic around anyway, 
> and at that point, why not just use the Android toolchain?

Yes, NDK should always be the best in the situation of cross-compiling 
for android. Thanks again!

Regards,

Zhengwang

>
>
> thanks,
> Steve
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