PyBoy•5mo ago

Brainstorming: adapting lcd.py to android

Hi everyone!

I've made some progress adapting pyboy to android using kivy/buildozer.
It works perfectly on some games, but unfortunately not on the one im interested, which is pokemon crystal.

I get consistent crashes on the same frames everytime. For example, on the loading screen when suicune is running and you have to press start.

The logs point to pyboy/core/lcd.so everytime, probably because it is trying to access memory which doesnt exist.

It is really difficult to debug because i havent found the way to make a print which i can see while running on android. It doesnt crash on desktop.

I feel really stuck on this, i was hoping you could give me some ideas to either fix it (i can addapt lcd.py) or either debugging it. Every bit of help is welcome!

Here are the crashing logs:

07-20 15:33:15.749 18477 18477 F DEBUG : NOTE: /data/data/org.test.myapp/files/
app/_python_bundle/site-packages/kivy/_clock.so
07-20 15:33:15.749 18477 18477 F DEBUG : NOTE: /data/data/org.test.myapp/files/
app/_python_bundle/site-packages/numpy/random/bit_generator.so
07-20 15:33:15.749 18477 18477 F DEBUG : NOTE: /data/data/org.test.myapp/files/
app/_python_bundle/site-packages/pyboy/core/lcd.so
07-20 15:33:15.749 18477 18477 F DEBUG : NOTE: /data/data/org.test.myapp/files/
app/_python_bundle/site-packages/pyboy/core/mb.so
07-20 15:33:15.749 18477 18477 F DEBUG : NOTE: /data/data/org.test.myapp/files/
app/_python_bundle/site-packages/pyboy/pyboy.so
07-20 15:33:15.749 18477 18477 F DEBUG : #00 pc 000000000001c9ac /data/data/
org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/lcd.so
07-20 15:33:15.749 18477 18477 F DEBUG : #01 pc 000000000001c228 /data/data/
org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/lcd.so
07-20 15:33:15.749 18477 18477 F DEBUG : #
07-20 ... And more, but im on the word limit already

Screenshot_2025-07-20-15-36-42-956_org.test.myapp.jpg

sergiomelero4OP•7/20/25, 1:59 PM

More info:
It crashes on tick()
It doesnt crash if render=False

Sky•7/20/25, 7:09 PM

Have you tried adding a bootrom? I would also see if for some reason, you get a similar error on gold, which is also playable with cgb = False

Bækalfen•7/20/25, 7:10 PM

Hmm. It's really strange that it doesn't fail immediately if so

Bækalfen•7/20/25, 7:11 PM

Can you try this? https://github.com/mattcurrie/cgb-acid2/releases/download/v1.1/cgb-acid2.gbc

Bækalfen•7/20/25, 7:11 PM

It's just a graphics test ROM https://github.com/mattcurrie/cgb-acid2

GitHub

GitHub - mattcurrie/cgb-acid2: 😀 The Acid2 test, now for Game Bo...

The Acid2 test, now for Game Boy Color!

. Contribute to mattcurrie/cgb-acid2 development by creating an account on GitHub.

Bækalfen•7/20/25, 7:11 PM

It would be really helpful if you can post the whole stacktrace. Doesn't matter if it's long

Bækalfen•7/20/25, 7:12 PM

Did you compile for 64-bit?

BBækalfen Hmm. It's really strange that it doesn't fail immediately if so

sergiomelero4OP•7/28/25, 9:38 AM

Hi again guys! Sorry for the delay.
I tried the Acid2 test and it crashes imediatelly after the pyboy intro. The logs are mostly the same as in pokemon crystal:

#00 pc 000000000001c9d8 /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/lcd.so
#01 pc 000000000001c23c /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/lcd.so
#02 pc 000000000001866c /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/lcd.so
#03 pc 0000000000016c48 /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/mb.so
#04 pc 0000000000033e64 /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/pyboy.so
#05 pc 00000000000344bc /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/pyboy.so
#06 pc 00000000000475d8 /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/pyboy.so
#07 pc 0000000000012310

sergiomelero4OP•7/28/25, 9:39 AM

/data/data/org.test.myapp/files/app/_python_bundle/site-packages/numpy/random/bit_generator.so
#08 pc 00000000001f4550 /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (_PyObject_MakeTpCall+328)
#09 pc 00000000002cc12c /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (_PyEval_EvalFrameDefault+17704)
#10 pc 00000000002c7b64 /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so
#11 pc 000000000001cffc /data/data/org.test.myapp/files/app/_python_bundle/site-packages/kivy/_clock.so
#12 pc 0000000000022e18 /data/data/org.test.myapp/files/app/_python_bundle/site-packages/kivy/_clock.so
#13 pc 0000000000034680 /data/data/org.test.myapp/files/app/_python_bundle/site-packages/kivy/_clock.so
#14 pc 00000000001f49e8 /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (PyObject_Vectorcall+72)
#15 pc 00000000002cc12c /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (_PyEval_EvalFrameDefault+17704)
#16 pc 00000000002c7a34 /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (PyEval_EvalCode+268)
#17 pc 0000000000318938 /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (_PyRun_SimpleFileObject+1188)
#18 pc 00000000003191fc /data/app/zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libpython3.11.so (PyRun_SimpleFileExFlags+60)
#19 pc 0000000000002740 /data/app/~~zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libmain.so (SDL_main+2664) (BuildId: 530c351246f588e0e63a15aec80493b9a9dd3d0f)
#20 pc 00000000000b10f4 /

sergiomelero4OP•7/28/25, 9:39 AM

data/app/~~zi0lZx0kJb2miHMfChB7EQ==/org.test.myapp-3gA0qvgT1HaYFz4CwOB5_w==/lib/arm64/libSDL2.so (Java_org_libsdl_app_SDLActivity_nativeRunMain+772) (BuildId: d1fc1a1b5aeed6101dd03188f643f3403d18d80e)
#21 pc 000000000037ef70 /apex/com.android.art/lib64/libart.so (art_quick_generic_jni_trampoline+144) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#22 pc 0000000000368a40 /apex/com.android.art/lib64/libart.so (art_quick_invoke_static_stub+640) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#23 pc 0000000000361e5c /apex/com.android.art/lib64/libart.so (bool art::interpreter::DoCall<false>(art::ArtMethod, art::Thread, art::ShadowFrame&, art::Instruction const, unsigned short, bool, art::JValue)+2048) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#24 pc 0000000000770ba4 /apex/com.android.art/lib64/libart.so (void art::interpreter::ExecuteSwitchImplCpp<false>(art::interpreter::SwitchImplContext*)+12208) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#25 pc 00000000003815d8 /apex/com.android.art/lib64/libart.so (ExecuteSwitchImplAsm+8) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#26 pc 000000000000cddc <anonymous:7d5a17e000> (org.libsdl.app.SDLMain.run+0)
#27 pc 00000000003535dc /apex/com.android.art/lib64/libart.so (artQuickToInterpreterBridge+1932) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#28 pc 000000000037f098 /apex/com.android.art/lib64/libart.so (art_quick_to_interpreter_bridge+88) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#29 pc 0000000002004568 /memfd:jit-cache (deleted) (offset 0x2000000) (java.lang.Thread.run+136)
#30 pc 0000000000368774 /apex/com.android.art/lib64/libart.so (art_quick_invoke_stub+612) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#31 pc 0

sergiomelero4OP•7/28/25, 9:40 AM

000000000353f24 /apex/com.android.art/lib64/libart.so (art::ArtMethod::Invoke(art::Thread, unsigned int, unsigned int, art::JValue, char const)+132) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#32 pc 0000000000947748 /apex/com.android.art/lib64/libart.so (art::detail::ShortyTraits<(char)86>::Type art::ArtMethod::InvokeInstance<(char)86>(art::Thread, art::ObjPtr<art::Object>, art::detail::ShortyTraits<>::Type...)+60) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#33 pc 0000000000636e80 /apex/com.android.art/lib64/libart.so (art::Thread::CreateCallback(void)+1344) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#34 pc 0000000000636930 /apex/com.android.art/lib64/libart.so (art::Thread::CreateCallbackWithUffdGc(void)+8) (BuildId: 4ccb65ae9ac5ad5da3af5a342d5b0b92)
#35 pc 0000000000070578 /apex/com.android.runtime/lib64/bionic/libc.so (__pthread_start(void)+200) (BuildId: bc5c61ed852b3f4266cdfdd25499ef95)
#36 pc 0000000000061910 /apex/com.android.runtime/lib64/bionic/libc.so (__start_thread+64) (BuildId: bc5c61ed852b3f4266cdfdd25499ef95

Bækalfen•7/28/25, 9:40 AM

Can you send the log as a file?

sergiomelero4OP•7/28/25, 9:40 AM

Oh sorry, of course

Bækalfen•7/28/25, 9:42 AM

Can you try the black/white version while you’re at it? https://github.com/mattcurrie/dmg-acid2

GitHub

GitHub - mattcurrie/dmg-acid2: 😀 The Acid2 test, now for the ori...

The Acid2 test, now for the original Game Boy!

GitHub - mattcurrie/dmg-acid2: The Acid2 test, now for the original Game Boy!

Bækalfen•7/28/25, 9:43 AM

Then we can maybe find out if it’s in the color code or the general code

Bækalfen•7/28/25, 9:44 AM

Also, what parameters are you supplying PyBoy(…)?

sergiomelero4OP•7/28/25, 9:45 AM

Here is the extended version with adb-logcat, ibelieve the crash starts with /data/data/org.test.myapp/files/app/_python_bundle/site-packages/pyboy/core/lcd.so

pyboyacid2crash-logs.txt40.49KB

sergiomelero4OP•7/28/25, 9:45 AM

And it is compiled for arm64 v8a

sergiomelero4OP•7/28/25, 9:46 AM

This is my pyboy instance: self.pyboy = PyBoy(self.rom_path, window="null", sound_emulated=True, sound_volume=100)

sergiomelero4OP•7/28/25, 9:50 AM

Black and wiki version working just fine!

Screenshot_2025-07-28-11-49-58-302_org.test.myapp.jpg

Bækalfen•7/28/25, 9:55 AM

How about dmg-acid2, but set : ?

sergiomelero4OP•7/28/25, 10:24 AM

Still crashes on cgb=True

pyboycrystalcrash-log.txt5.56KB

Bækalfen•7/28/25, 10:46 AM

Ok, I kind of expected that. So it’s narrowing down to the cgb code in LCD

Bækalfen•7/28/25, 7:47 PM

I can see there are references to functions in other libraries. Can you remove this line from :

Bækalfen•7/28/25, 7:47 PM

Or otherwise make sure symbols are included

Bækalfen•7/28/25, 7:48 PM

If so, it'll probably give the specific function and line that fails

BBækalfen I can see there are references to functions in other libraries. Can you remove t...

sergiomelero4OP•8/1/25, 2:34 PM

Unfortunately I cannot debug or log while running on android

If I take that line away, it crashes automatically while running adb logcat.
I've tried writting the logs on a file inside the phone, but it also crashes, I think it messes with kivy's clock or something.

Bækalfen•8/1/25, 7:01 PM

I can't imagine how adding the debug symbols back in (removing the '-s -w' flags) would make it crash

sergiomelero4OP•8/22/25, 6:58 AM

Hi guys! Just a little update, I'm still working on this:

Now i can see which line of lcd.c is crashing.

Which is: (unlikely(__pyx_get_slice_count(memview) <= 0))

As it only crashes in color mode and android, it is most likely caused by this memoryviews: self._tilecache1 = memoryview(self._tilecache1_raw).cast("B", shape=(TILES * 8, 8))
self._tilecache1_64 = memoryview(self._tilecache1_raw).cast("Q", shape=(TILES * 8,))

This kind of escapes my "technical level"

, but basically the b cast over a Q array only occurs once in the game boy color code in lcd.py, and is something that should not break in Desktop because it handles is automatically, but i can break in arm64 (Sorry for the poor explanation).

Bækalfen•8/22/25, 3:14 PM

Great! Can you send your lcd.c? Also, do you have a line number?

sergiomelero4OP•8/23/25, 12:58 PM

The crash line is 55185, thanks a lot for all the help!

lcd.c2.52MB

Bækalfen•8/23/25, 1:18 PM

Of course

Do you have the rest of the stack trace? It’s a common function called from several places

sergiomelero4OP•8/23/25, 1:39 PM

Yes, im extracting all the info! will be ready in a moment

sergiomelero4OP•8/23/25, 1:45 PM

stacktrace_pyboy_android_crash.txt6.75KB

sergiomelero4OP•8/23/25, 1:47 PM

tick() => scanline() => scanline_background() => tilecache = self._tilecache0

sergiomelero4OP•8/23/25, 2:11 PM

I believe all these problems happen because I'm using an old cython version (0.29.36, its the default one) in the buildozer environment. I tried the recommended one for pyboy once, but didnt make it work, maybe I'll try again now.

sergiomelero4OP•8/23/25, 2:28 PM

So I put tilecache = _tilecache0[:] and its working for the first time (its still laggy, bc i got ride of a lot of optimizations so i could see logs) im gonna cry

Screenshot_2025-08-23-16-26-25-893_org.test.myapp.jpg

Bækalfen•8/23/25, 3:27 PM

Awesome!

Bækalfen•8/23/25, 3:28 PM

Very weird with that fix. I don't really know why

Bækalfen•8/23/25, 3:28 PM

PyBoy is very particular about the Cython version. But in that case, the compile should fail

Bækalfen•8/23/25, 7:01 PM

@sergiomelero4 What happens if you change this in :

Bækalfen•8/23/25, 7:03 PM

Or maybe add the 4 lines to

Bækalfen•8/23/25, 7:06 PM

Interestingly, there is a difference between my and yours. Yours call while mine calls .
I think the crash happens because your code tries to decrement the reference count for an uninitialized memview. While mine correctly clears it.

Bækalfen•8/23/25, 7:08 PM

You also have a lot more checks and debug stuff. But that's maybe expected?

BBækalfen Interestingly, there is a difference between my `lcd.c` and yours. Yours call `_...

sergiomelero4OP•8/24/25, 9:32 AM

This is the key to the thing! my cython version generates unsafer c code. PYX_XDEC_MEMVIEW is found in my cython release and PYX_XCLEAR_MEMVIEW is in the 3.0.6 one.
I believe it is a known issue, this stackoverflow post mentions it: “The reference counting for memoryviews has been slightly rearranged for Cython 3.0 (mainly to avoid a few corner cases where references could be leaked) so it's not completely surprising that it's changed from 0.29.x.” https://stackoverflow.com/questions/76972950/cython-returned-memoryview-is-always-considered-uninitialized?utm_source=chatgpt.com

Stack Overflow

Cython returned memoryview is always considered uninitialized

Similar to Cython Memoryview as return value, but I didn't see a solution other than hacking the generated C code.
I'm using Cython 3.0, but it looks like the result is the same with <3.
Here's an

sergiomelero4OP•8/24/25, 9:34 AM

unfourtunately when i tried to use the 3.0.6 numpy gave even more problems than pyboy

sergiomelero4OP•8/24/25, 9:46 AM

https://github.com/kivy/python-for-android/issues/2919 cython 3 upwards is not supported on python for android, guess I'll have to stick with 0.29.x for now

GitHub

Support Cython 3 · Issue #2919 · kivy/python-for-android

[This is an issue well-known to the developers, but I don't see it documented in the Issues database.] Cython 3 was released in July 2023. It isn't compatible with python-for-android and/or...

Bækalfen•8/24/25, 8:00 PM

Interesting. At least you have a workaround for now

Bækalfen•8/25/25, 6:39 PM

I won't promise anything, but I'm trying to refactor the part you're having problems with

Bækalfen•8/27/25, 7:15 AM

@sergiomelero4 Check out the branch. I've put my refactor there along with some unrelated stuff. Tell me how it goes https://github.com/Baekalfen/PyBoy/tree/fix_n_perf