IssueTracker

Using the GCC 4.7 toolchain included in the NDK r8d, shared libraries that include <iostream> code will fail to load on devices running Android 2.2 (and possibly lower - couldn't test that).

The last message in LogCat is:
D/dalvikvm(): Trying to load lib /data/data/com.test/lib/libTestLib.so 0x46276110
i.e. it does not get past the loading stage; there is no 'Added shared lib' message.

- Devices running Android 2.3 and above do not seem to be affected.
- Also, libraries that do not include <iostream> don't seem to be affected either.
- The problem does not occur when using the GCC 4.6 toolchain.

Overall, this seems like a critical issue which currently renders the GCC 4.7 toolchain unusable for compiling code that is supposed to be used on devices with Android 2.2.

The following is a minimal example to reproduce the issue:

-------------------------------------------------------
TestActivity.java:
------------------
package com.test;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class TestActivity extends Activity {
  static {
    System.loadLibrary("TestLib");
  }
       
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d("TestActivity", "Hello, world!");
  }
}


TestLib.cpp:
------------
#include <iostream>


Android.mk:
-----------
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := TestLib
LOCAL_SRC_FILES := TestLib.cpp
include $(BUILD_SHARED_LIBRARY)


Application.mk:
---------------
APP_ABI := armeabi-v7a
APP_STL := gnustl_static # or _shared, doesn't matter
NDK_TOOLCHAIN_VERSION=4.7 # if this is commented out, everything works
-------------------------------------------------------


Digging deeper into the <iostream> source code, I found out that the issue can be traced back to the following code snippet:

--------
namespace std
{
        struct ios_base // from <bits/ios_base.h>
        {
                struct Init
                {
                  Init();
                };

        };

        static ios_base::Init __ioinit;
}
--------

- By replacing the contents of TestLib.cpp with only the above code snippet, the library will fail to load.

- If, additionally, a dummy implementation of std::ios_base::Init::Init() is provided, the library will load successfully.
  std::ios_base::Init::Init() {}

- Renaming the namespace from 'std' to another name, e.g. 'xstd', will naturally cause the linker to complain:
  error: undefined reference to 'xstd::ios_base::Init::Init()'

This leads me to believe that there is an issue with the implementation of std::ios_base::Init::Init() in the GCC 4.7 sources (as opposed to the GCC 4.6 sources). After checking out the NDK toolchain sources, I could not detect any differences between the different versions of ios_init.cc, where the Init() constructor is defined. That implies that there is an issue with a function used inside the constructor, and this is where I stopped investigating further.