No merge between the CMake flags and the default flags

[nguillot]

Studio Build: #AI-145.3276617
NDK: 13.0.3315539
Version of Gradle Plugin: 2.2.0
Version of Gradle: 2.14.1
Version of Java: 1.8.0_76
OS: Mac OS 10.12

Steps to Reproduce:

1. Download the project https://github.com/nguillot/android-cmake
2. checkout the c++_shared branch
3. build the project
4. in command line do
   cat /Users/nicolasguillot/Documents/projets/android-cmake/core/lib/android/.externalNativeBuild/cmake/debug/x86/android_gradle_build.json

Expected result:
The flags element is build according to the CMake value.

Result
the flags element contains -fno-rtti -std=c++11 --std=c++11 -frtti
I added the last two in the root CMake. By default it seems that we have the -fno-rtti flag which does not take into account the CMake flag -frtti.

[nguillot]

I observed the same result when using the Gradle cppFlags flags.

[nguillot]

I'm a newbies c++ dev. And I first observed this error on a compilation error. Android Studio printed the flags.

[DanAlbert]

What's the problem here? The early -fno-rtti is overridden by the later -frtti. It's not possible to prevent the prior -frtti from being emitted entirely by using cflags. You need to use ANDROID_CPP_FEATURES if you need that.

Note that pretty soon we're just going to drop the default of rtti and exceptions being off for cmake. #212.

[nguillot]

Like I've said before I'm not an experienced C++ dev. An it looks strange to me to have a flag and this opposite. If you remove th default it will be clearer. Furthermore, you assure me that in our case the latest flag win, you can close the issue. Thanks.

[DanAlbert]

Yes, the last flag wins when it comes to -frtti.