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3 reasons: - This is what encode_remote_object() does. I see no reason a NULL local object should be encoded differently than a NULL remote object. - This is what Parcel.cpp does when flattening a NULL binder [1]. This is contrary to what is said in PR #99 [2]; I'm not sure why PR #99 said it uses BINDER_TYPE_HANDLE. - More importantly, BINDER_TYPE_HANDLE number 0 does NOT represent a NULL binder. According to the comment at [3], handle number 0 actually represent the context manager. So, by sending BINDER_TYPE_HANDLE number 0, we're sending context manager, not a NULL binder. [1]: https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-14.0.0_r1/libs/binder/Parcel.cpp#277 [2]: https://github.com/mer-hybris/libgbinder/pull/99 [3]: https://android.googlesource.com/platform/frameworks/native/+/refs/tags/android-14.0.0_r1/libs/binder/ProcessState.cpp#336 Origin: vendor Bug-UBports: https://gitlab.com/ubports/development/core/packaging/libgbinder/-/merge_requests/9#note_2138653925 Forwarded: https://github.com/mer-hybris/libgbinder/pull/135
GLib-style interface to binder (Android IPC mechanism) Key features: 1. Integration with GLib event loop 2. Detection of 32 vs 64 bit kernel at runtime 3. Asynchronous transactions that don't block the event thread 4. Stable service manager and low-level transaction APIs Android keeps changing both low-level RPC and service manager protocols from version to version. To counter that, libgbinder implements configirable backends for different variants of those, and yet keeping its own API unchanged. Configuration is loaded from [Protocol] and [ServiceManager] sections of /etc/gbinder.conf file. The keys are binder device names or the special Default value, the value is the identifier of the protocol or service manager variant, respectively. In addition to reading /etc/gbinder.conf if it exists, /etc/gbinder.d directory is scanned for .conf files, the file list is sorted, files are loaded one by one, overwriting the entries loaded from /etc/gbinder.conf or from the previously processed file. Known protocol and service manager variants are aidl, aidl2, aidl3 and hidl. This list is expected to expand further in the future. The default configuration is as follows: [Protocol] Default = aidl /dev/binder = aidl /dev/hwbinder = hidl [ServiceManager] Default = aidl /dev/binder = aidl /dev/hwbinder = hidl Alternatively and preferably, one can specify the desired Android API level: [General] ApiLevel = 29 and let libgbinder pick the appropriate preset. Full list of presets can be found in src/gbinder_config.c