    Android System Image Issues
    ===========================

    This document contains a list of known issues in existing Android
    system images that NDK developers should be aware of.

    I. Android 1.5 System Issues:
    -----------------------------

    The following issues correspond to the official Android 1.5
    system images:

    No standard C++ library support:
    --------------------------------

    The Android 1.5 system does not use any C++ standard library, and does
    not provide one to applicative native code. Instead, a very limited set
    of headers are provided (see docs/STABLE-APIS.html) which correspond to
    the C++ support code used to build the Android platform.

    It is possible to hack existing C++ STL implementations to work on top
    of this, but this is not supported yet. We recommend trying with uSTL
    and STLport at this point if you really need this.

    No support for C++ exceptions and RTTI:
    ---------------------------------------

    The Android 1.5 system image lacks several features necessary to reliably
    implement C++ exceptions and RTTI. C++ code that depends on these features
    will simply not link or run appropriately on Android 1.5

    C Library limitations:
    ----------------------

    The C library doesn't try to implement every feature under the sun.
    Most notably, pthread cancellation is not supported. A detailed overview
    of the C library and its design is available in docs/system/libc/OVERVIEW.html

    No SysV IPCs in C library:
    --------------------------

    Unix System V Inter-Process Communication APIs (e.g. semget()) are
    intentionally not available from the C library, to avoid denial-of-service
    issues. See docs/system/libc/SYSV-IPC.html for details.

    C Library bug: getservbyname() returns port number in incorrect order:
    ----------------------------------------------------------------------

    The Android 1.5 C library function getservbyname() returns the port number
    corresponding to a given network service in incorrect order. The function
    stores its result in a 'struct servent' structure, and the port number in
    its 's_port' field.

    The standard mandates that this value is stored in network order (and thus
    should be converted to host order through ntohs()). However, the 1.5
    implementation is buggy and returns the number.

    This bug is fixed in later releases of the platform, and applications
    should not depend on the wrong behaviour in the future. Avoid using this
    function if possible; if this is not possible, try to use a small wrapper
    like the following one:

    static struct servent*
    my_getservbyname(const char*  name, const char*  proto)
    {
        static int       has_bug = -1;
        struct servent*  ret;

        if (has_bug < 0) {
            ret = getservbyname("http",NULL);
            has_bug = (ret == NULL || ret->s_port == 80);
        }

        ret = getservbyname(name, proto);
        if (has_bug)
            ret->s_port = htons(ret->s_port);
    }

    (the returned struct servent is thread-local and can be modified by the
     caller. It will be over-written on the next call to the function though).

    Dynamic Linker limitations:
    ---------------------------

    The Android dynamic linker in 1.5 has many important limitations:

    - No support for LD_LIBRARY_PATH, LD_PRELOAD, RTLD_LOCAL and many
      other options.

    - Static C++ constructors in executables are called twice due to a bug
      in the C library initialization sequence. However, static C++
      constructors in shared libraries are only called once.

    - Static destructors are never called at the moment, either at program
      exit, or when dlclose() is called.

    - dlerror() reporting is very limited and only provides a few generic
      error messages that make it difficult to know why a dynamic load/link
      operation failed. Most of the time, the culprit is a missing symbol.

    - A bug prevents one application shared library from depending on another
      one. For example, if you build both libfoo.so and libbar.so for your
      application, and list libfoo.so as a dependency for libbar.so in
      bar/Android.mk (with LOCAL_SHARED_LIBRARIES := foo), then loading
      libbar.so will always fail, even if you have already loaded libfoo.so
      in your process.