my application using ctypes crashes on Kivy 1.9.2 and not on 1.8

[gued100x12]

Hi,

I would like to share an issue i am getting while building an APK using the latest python-for-android package (1.9.x). The same code works fine on an old version of Kivy (1.8.).

I will try to describe how i get to this and please let me know if more clarification is needed:

1. So, I am a C code where i am calling a callback function defined in python.
   Basically the code consists of (mydll.c):

`
typedef int (*callback_type)(float, float);

DLLEXPORT int our_callback(callback_type callbackHandler)
{
float a = 10;
float b = 50;
float count = 0;

for (count=0; count<60;count=count+10)
{
(*(callbackHandler))((a+count),b);
}

return 0;
`

2. The python code consists of (main.py):

`
callback_type = CFUNCTYPE(c_int, c_float, c_float)

if name == 'main':

def greater_than(a,b):
    if a > b:
        Logger.info(u"GUED case1 {} is greater than {}".format(a,b))
        return 1
    else:
        Logger.info(u"GUED case1 {} is lower than {}".format(a,b))          
        return 0

    my_ctype_lib = cdll.LoadLibrary(os.path.join("my_clibrary"))
my_ctype_lib.our_callback.argtypes = [callback_type]

ret = my_ctype_lib.our_callback(callback_type(greater_than))
Logger.info(u"GUED ret= {}".format(ret))

`

Find attached the complete files:
python_ctype.zip

This works perfectly on PC (win32) and on android when using Kivy 1.8.
But when i build an APK using Kivy 1.9, i am getting a crash in the c library when referring to the callback (see the attached log file retrieved from logcat).
log_python4android_Kivy1.9_crash.txt

3. How did i create the 1.9 Kivy distribution?
   I used the following command:
   python-for-android create --dist_name=batch2 --bootstrap=pygame -- requirements=hostpython2,python2,pyjnius,sdl,pygame,android,kivy

I am running out of ideas here and wondering what could have changed between 1.8 and 1.9?
Am i doing something wrong? or could it be that i am missing some modules?
I've checked the Cython version, i am using 0.23.

Let me know if you need more info.

Any help would be highly appreciated:-).
Thanks in advance.

Want to back this issue? Post a bounty on it! We accept bounties via Bountysource.

[gued100x12]

Additional info:
I found another reported issue similar to mine (looks like closed because of lake of info):
#401.
The behaviour seems to be the same.

[uberwoozle]

This may be an issue with the python distribution itself. It is likely the python distribution being used is using 'malloc' instead of 'mmap' for its 'ffi_closure_alloc/free' function which is called by '_ctypes_alloc_callback'. Android's malloc does not grant PROT_EXEC to allocated memory, which is necessary for the python code to be called. It may be as easy as using the implementation in the file 'malloc_closure.c'.

[gued100x12]

Thanks for your comment. Does it be mean that I will need to update the python distribution for android? I am quite new in the Kivy world, so i will likely need step by step help here:-). In past we could build the distribution with the build script. Now it seems that we can get the hole package through an exe. I don't see how the modify a particular file. Any idea why to update a exiting python distribution for android?

[inclement]

Closing as stale, I'm not aware of any issue like this on the master branch.