CODEWITHSUNDEEP
androidc++function
sir mordred
sir mordred

Reputation: 161

about mangled name of functions in c++

ı have closed source shared library that links against libmedia.so from android

but unforunatly in >android 5.0 ABI changes that made by google broke my closed source lib (thanx google)

now ı have the following error --> dlopen failed cannot locate symbol "_ZN7android11MediaPlayer13setDataSourceEPKcPKNS_11KeyedVectorINS_7String8ES4_EE" referenced by "mylib.so"

then ı hexedited my closed source library(mylib.so) to load myhack.so (that ı built myself) instead of libmedia.so (so ı simply made a trick)

here is the Android.mk of myhack.so library:

include $(CLEAR_VARS)
LOCAL_SRC_FILES := hack.cpp
LOCAL_SHARED_LIBRARIES := libmedia
LOCAL_MODULE := myhack
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
include $(BUILD_SHARED_LIBRARY)

and here is the hack.cpp:

extern "C" void _ZN7android11MediaPlayer13setDataSourceERKNS_2spINS_17IMediaHTTPServiceEEEPKcPKNS_11KeyedVectorINS_7String8ES9_EE();
extern "C" void _ZN7android11MediaPlayer13setDataSourceEPKcPKNS_11KeyedVectorINS_7String8ES4_EE() {
    return _ZN7android11MediaPlayer13setDataSourceERKNS_2spINS_17IMediaHTTPServiceEEEPKcPKNS_11KeyedVectorINS_7String8ES9_EE();
}

let me explain a bit:

1-as I said I hexedited my closed source lib to load myhack.so instead of libmedia.so (source file and android.mk file of myhack.so are in above)

2-I linked myhack.so to libmedia.so(as you can see) to provide other libmedia functions via myhack.so

LOCAL_SHARED_LIBRARIES := libmedia

3- lost symbol: _ZN7android11MediaPlayer13setDataSourceEPKcPKNS_11KeyedVectorINS_7String8ES4_EE

current symbol in libmedia.so: _ZN7android11MediaPlayer13setDataSourceERKNS_2spINS_17IMediaHTTPServiceEEEPKcPKNS_11KeyedVectorINS_7String8ES9_EE

so if lost symbol is called, it will return original function

my question is should I use extern "C" void or extern "C" int..... int or void? which one? setDataSource is a function and I dont think it is returning integer value so it should be void ı think but ım not %100 sure

could anyone help me please? thanx

Upvotes: 2

Views: 652

Answers (1)

marcinj
marcinj

Reputation: 50016

Sooner or later you will get in troble with it. I remember problems with skia on project I work on. Some vendors were doing small changes with interfaces and that was causing various crashes.

To find return type you can investigate sources for android, steps are below:

You can use https://demangler.com/, to see signature of your function, it should be:

android::MediaPlayer::setDataSource(android::sp<android::IMediaHTTPService> const&, char const*, android::KeyedVector<android::String8, android::String8> const*)

now lets search android sources for such signature, you can find it here:

http://androidxref.com/6.0.1_r10/xref/frameworks/av/media/libmedia/mediaplayer.cpp#148

so its return type is status_t, which is typedef int status_t;, so as you have assumed its int.

Upvotes: 1

Related Questions