Android NDK: exceptions crash on ARM 32bit when compiled with clang and c++_shared

At work we use clang and STL standard library from c++_shared included in the NDK. This week we have got nasty surprise when we were trying to run some code that was throwing an exception in our async library. This seemed to happend only on ARM 32bit devices. After a bit of digging, we have found bug report that describes more or less our situation.

We have built small test program that let us test few scenarios and that this is really a bug in STL library shipped with Android NDK:

// jni/hello.cpp
#include <stdexcept>
#include <iostream>
int main() {
  std::cerr << "1\n";
  try {
    throw std::runtime_error("A"); // crash! but only on arm 32bit, and when compiled with clang
  } catch (std::exception& e) {}
  std::cerr << "2\n";
}

## jni/Android.mk
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := hello
LOCAL_SRC_FILES := hello.cpp
LOCAL_CPPFLAGS := -frtti -fexceptions -fPIE -pie
LOCAL_LDLIBS := -llog -pie
include $(BUILD_EXECUTABLE)

## jni/Application.mk
APP_STL:=c++_shared
APP_ABI:=armeabi-v7a
NDK_TOOLCHAIN_VERSION:=clang

To fix it, we had to switch from c++_shared to c++_static. However, because we had multiple shared libraries, we had to change the way we build our code, so that we don’t break ODR. Instead of building multiple shared libraries, we now build all libraries statically and link them together into one shared library.

This bug was recently fix, and should be available in the next Android NDK release (r12?).