Cannot build app.so with Dart 2.9.2: "Can't load Kernel binary: Invalid SDK hash"

[apiraino]

Hey,

I've updated the Dart+Flutter SDK to the very latest stable:

$ flutter --version
Flutter 1.20.3 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 216dee60c0 (9 days ago) • 2020-09-01 12:24:47 -0700
Engine • revision d1bc06f032
Tools • Dart 2.9.2

I can compile the kernel snapshot, but I can't compile anymore the app.so.

$ gen_snapshot_linux_x64 \
  --causal_async_stacks \
  --deterministic \
  --snapshot_kind=app-aot-elf \
  --elf=build/app.so --strip \
  --sim_use_hardfp \
  --no-use-integer-division build/kernel_snapshot.dill 
Can't load Kernel binary: Invalid SDK hash.

Can you detail a little bit how the gen_snapshot_linux_x64 binary you provide is generated and why it fails? Do I have to match the exact same Dart SDk version as yours?

Thanks!

[apiraino]

Possibly related to this

[ardera]

Hey,

I can compile the kernel snapshot, but I can't compile anymore the app.so.

$ gen_snapshot_linux_x64 \
  --causal_async_stacks \
  --deterministic \
  --snapshot_kind=app-aot-elf \
  --elf=build/app.so --strip \
  --sim_use_hardfp \
  --no-use-integer-division build/kernel_snapshot.dill 
Can't load Kernel binary: Invalid SDK hash.

That's not your fault. gen_snapshot_linux_x64 is a side-product of the flutter engine compilation. A flutter engine version (which is a commit hash) maps one-to-one to an SDK version (which is a commit hash as well). So one specific version of gen_snapshot_linux_x64 can only accept kernel_snapshot.dill's from one specific version of the flutter SDK. This error message is basically saying that the version of the flutter SDK that built this kernel_snapshot.dill is wrong & not the version it expects to find.

TL;DR there was an update of the stable flutter SDK 9 days ago and I haven't yet updated the engine binaries. I'm compiling right now. These version checks are new and I haven't yet found a way to get notified of flutter stable updates

[apiraino]

Ah thank you so much for clarifying, now the whole picture is getting clearer (see also the answer I received in the above linked dart pub issue). I was confused because I thought that "stable is stable" and a minor version update would make no difference :-)

Next release of the gen_snapshot_linux_x64 you're going to do, it would be great if you can pin the exact SDK version (or version range) that can be used.

Also, being able to build that by myself would be a huge plus, but I understand that documenting the process will take some time :-)

Thank you so much!

[ardera]

Next release of the gen_snapshot_linux_x64 you're going to do, it would be great if you can pin the exact SDK version (or version range) that can be used.

That's a good idea, I'll do that

Also, being able to build that by myself would be a huge plus, but I understand that documenting the process will take some time :-)

To do that, just build the engine (in release mode). After you've done that, the gen_snapshot executable is located inside the clang_x64 directory in the output directory.

Building the engine is kinda complicated and takes a long time. #49 is an open issue about that, you can find some instructions there.

[ardera]

Next release of the gen_snapshot_linux_x64 you're going to do, it would be great if you can pin the exact SDK version (or version range) that can be used.

Some info about that: Invalid SDK hash actually means Invalid dart SDK hash. I can (and will) give the exact dart SDK version that's compatible with a specific set of engine binaries (see dart-sdk.version). It's impossible to specify exact flutter SDK version ranges though. Best I can do is a lower bound, i.e. specifying that flutter SDK 1.20.3 started using engine X and dart SDK Y.

Btw you can also see the engine version your flutter SDK is using when running flutter upgrade.

[apiraino]

I have downloaded the new binary and successfully build the app.so, great job! Now I know that I must not change a single bit in this workflow :-)

In the following days I will try running my Flutter app and see if I can make run on the Rpi4. If it's ok for you, I'd keep this issue open in case I have further questions. I will close it anyway when I'll be done.

Thanks 👍

[ardera]

In the following days I will try running my Flutter app and see if I can make run on the Rpi4. If it's ok for you, I'd keep this issue open in case I have further questions. I will close it anyway when I'll be done.

Thanks 👍

Yep, sure. No problem