crash when mapping empty GstBuffer about gst1-java-core HOT 5 CLOSED

Hi! Thanks - I think! 😄 This is a weird one. Not sure if I know what the issue is here yet. Possibly a bug in JNA.

I can replicate with this - can you?

for (int i = 0; i < 200; i++) {
  Buffer b = new Buffer(0);
  ByteBuffer data = b.map(true);
  if (data != null) {
    System.out.println("Got data of size : " + data.capacity());
  }
  b.unmap();
}
System.out.println("Done!");

However, this works - does it for you?

GstBufferAPI.MapInfoStruct mapInfo = new GstBufferAPI.MapInfoStruct();
for (int i = 0; i < 200; i++) {
  Buffer b = GstBufferAPI.GSTBUFFER_API.gst_buffer_new_allocate(null, 0, null);
  // mapInfo = new GstBufferAPI.MapInfoStruct();
  System.out.println("Mapping buffer : " + b.hashCode());
  boolean ok = GstBufferAPI.GSTBUFFER_API.gst_buffer_map(b, mapInfo, GstBufferAPI.GST_MAP_READ);
  if (ok) {
    System.out.println("OK");
    System.out.println(mapInfo);
   } else {
    System.out.println("Not OK");
    System.out.println(mapInfo);
  }
  if (ok) {
    GstBufferAPI.GSTBUFFER_API.gst_buffer_unmap(b, mapInfo);
  }
}
System.out.println("Done!");

But uncommenting the line to create a new mapInfo every time around makes it crash. It's like it's something to do with the structure?

Thoughts?

from gst1-java-core.

I think the MapInfoStruct we inherited is too small. See -

https://github.com/gstreamer-java/gst1-java-core/blob/master/src/org/freedesktop/gstreamer/lowlevel/GstBufferAPI.java#L44
vs
https://github.com/GStreamer/gstreamer/blob/master/gst/gstmemory.h#L204

In the for loop above if you replace

mapInfo = new GstBufferAPI.MapInfoStruct();

with

mapInfo = new GstBufferAPI.MapInfoStruct(new Memory(200));

it doesn't crash, at least for me. You? That's not the actual size needed obviously! Just big enough. 😄

from gst1-java-core.

hey. yes, your snippets behave the same way here.
it does not crash when creating a MapInfoStruct with a Memory directly.

you are right, the structure we inherit is not correct, we are missing:

        public volatile Pointer[] user_data = new Pointer[4];
        
        public volatile Pointer[] _gst_reserved = new Pointer[GST_PADDING];

i added them, no crash anymore :)

from gst1-java-core.

PR coming up in minute.

guess we should look into all the structures and align them to gst-1.8...

from gst1-java-core.

Thanks! Didn't have time to work on a fix after finding the issue. An unexpected reason - weird that it's gone unnoticed for this long and not caused other issues. I assume with an empty buffer GStreamer might be doing something with those areas of the structure?

Checking all structures is on my list of jobs that need doing before 1.0 - it's just a matter of finding some free time for all the boring stuff! 😄

from gst1-java-core.