C++ support with the Android NDK
================================


The Android platform provides a very minimal C++ runtime support library
(/system/lib/libstdc++) and corresponding headers for it in the NDK.

I. C++ Exceptions support:
--------------------------

The NDK toolchain supports C++ exceptions, since NDK r5, however all C++
sources are compiled with -fno-exceptions support by default, for
compatibility reasons with previous releases.

To enable it, use the '-fexceptions' C++ compiler flag. This can be done
by adding the following to every module definition in your Android.mk:

    LOCAL_CPPFLAGS += -fexceptions

More simply, add a single line to your Application.mk, the setting will
automatically apply to all your project's NDK modules:

    APP_CPPFLAGS += -fexceptions

NOTE: The obsolete "arm-eabi-4.4.0" toolchain provided for backwards
      compatibility with this NDK does not support exceptions!


II. RTTI support:
------------------

Similarly, the NDK toolchain supports C++ RTTI (RunTime Type Information)
since NDK r5, but all C++ sources are built with -fno-rtti by default for
compatibility reasons. To enable it, add the following to your module
declarations:

    LOCAL_CPPFLAGS += -frtti

Or more simply to your Application.mk:

    APP_CPPFLAGS += -frtti


NOTE: The obsolete "arm-eabi-4.4.0" toolchain provided for backwards
      compatibility with this NDK does not support RTTI!


III. Selecting the C++ Standard Library Implementation:
-------------------------------------------------------

By default, the headers and libraries for the minimal C++ runtime system
library (/system/lib/libstdc++.so) are used when building C++ sources.

You can however select a different implementation by setting the variable
APP_STL to something else in your Application.mk, for example:

  APP_STL := stlport_static

To select the static STLport implementation provided with this NDK.
Value APP_STL values are the following:

   system              -> Use the default minimal C++ runtime library.
   stlport_static      -> Use STLport built as a static library.
   stlport_shared      -> Use STLport built as a shared library.

WARNING: IMPORTANT CAVEAT

     AT THE MOMENT, OUR STLPORT IMPLEMENTATION DOES NOT SUPPORT EXCEPTIONS
     AND RTTI. PLEASE BE SURE TO NOT USE -fexceptions OR -frtti IN ALL
     MODULES THAT USE IT.

WARNING: END OF IMPORTANT CAVEAT

  "stlport_shared" is preferred if you have several shared libraries in your
  project that use the C++ STL, because it avoids duplication of functions
  and more importantly of global variables (e.g. std::cout) in each one of
  them, which can have surprising results.

  On the other hand, you will have to load it explicitely when starting your
  application, as in the following example:

     static {
         System.loadLibrary("stlport_shared");
         System.loadLibrary("foo");
         System.loadLibrary("bar");
     }

  Where both "libfoo.so" and "libbar.so" depend on "libstlport_shared.so".

  Note that the shared library's name if "libstlport_shared.so" to avoid
  naming conflicts with certain Android system images which include a
  system-level libstlport.so (which happens to not be ABI-stable and
  cannot be used from NDK-generated machine code).

  "stlport_static" is preferred if you have only one shared library in your
  project: only the STL functions and variables you actually need will be
  linked to your machine code, reducing its code size, and you won't need
  to load the dynamic stlport_shared at startup.


IV. STLport-specific issues:
----------------------------

This NDK provides prebuilt static and shared libraries for STLport,
but you can force it to be rebuilt from sources by defining the following
in your environment or your Application.mk before building:

    STLPORT_FORCE_REBUILD := true

STLport is licensed under a BSD-style open-source license. See
sources/cxx-stl/stlport/README for more details about the library.


V. Future Plans:
----------------

  - Make STLport compatible with C++ exceptions and RTTI
  - Full GNU libstdc++ support
  - uSTL support?