bug: wallet.listUnspent() can throw RangeError(byteOffset) due to ChainPosition offset drift

[reez]

Problem

Calling wallet.listUnspent() can fail during Dart FFI decode with:

RangeError (byteOffset): Index out of range: index should be less than 1: 7

Stack trace

• Script.read (...)
• FfiConverterTxOut.read (...)
• FfiConverterLocalOutput.read (...)
• FfiConverterSequenceLocalOutput.read (...)
• Wallet.listUnspent (...)

Error Logs:

 Future<List<dynamic>> getUtxos() async {
    print('[DEBUG] Starting getUtxos()');
    List<dynamic> finalUtxos = [];

    print('[DEBUG] Fetching wallet UTXOs...');
    final walletUtxos = wallet.listUnspent();
    print('[DEBUG] Found ${walletUtxos.length} UTXOs in wallet');
    
    ...
}

I/flutter ( 6052): [DEBUG] Starting getUtxos()
I/flutter ( 6052): [DEBUG] Fetching wallet UTXOs...
I/flutter ( 6052): Error during _syncWallet: RangeError (byteOffset): Index out of range: index should be less than 1: 7
I/flutter ( 6052): #0      _byteDataByteOffsetCheck (dart:typed_data-patch/typed_data_patch.dart:5419:5)
I/flutter ( 6052): #1      _ByteDataView.getInt64 (dart:typed_data-patch/typed_data_patch.dart:5214:5)
I/flutter ( 6052): #2      Script.read (package:bdk_dart/bdk.dart:20644:61)
I/flutter ( 6052): #3      FfiConverterTxOut.read (package:bdk_dart/bdk.dart:3221:40)
I/flutter ( 6052): #4      FfiConverterLocalOutput.read (package:bdk_dart/bdk.dart:1711:44)
I/flutter ( 6052): #5      FfiConverterSequenceLocalOutput.read (package:bdk_dart/bdk.dart:25741:43)
I/flutter ( 6052): #6      FfiConverterSequenceLocalOutput.lift (package:bdk_dart/bdk.dart:25733:44)
I/flutter ( 6052): #7      rustCallWithLifter (package:bdk_dart/bdk.dart:22780:18)
I/flutter ( 6052): #8      Wallet.listUnspent (package:bdk_dart/bdk.dart:22316:12)
I/flutter ( 6052): #9      WalletService.getUtxos (package:flutter_wallet/services/wallet_service.dart:897:32)
I/flutter ( 6052): #10     SharedWalletState._syncWallet (package:flutter_wallet/wallet_pages/shared_wallet.dart:556:47)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): #11     WalletUiHelpers.handleRefresh (package:flutter_wallet/wallet_helpers/wallet_ui_helpers.dart:1166:7)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): #12     SharedWalletState.build.<anonymous closure> (package:flutter_wallet/wallet_pages/shared_wallet.dart:777:17)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): #13     RefreshIndicatorState._show.<anonymous closure>.<anonymous closure> (package:flutter/src/material/refresh_indicator.dart:579:40)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): 
I/flutter ( 6052): Sync error: Exception: Sync Error: RangeError (byteOffset): Index out of range: index should be less than 1: 7
I/flutter ( 6052): Stack trace: #0      SharedWalletState._syncWallet (package:flutter_wallet/wallet_pages/shared_wallet.dart:605:7)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): #1      WalletUiHelpers.handleRefresh (package:flutter_wallet/wallet_helpers/wallet_ui_helpers.dart:1166:7)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): #2      SharedWalletState.build.<anonymous closure> (package:flutter_wallet/wallet_pages/shared_wallet.dart:777:17)
I/flutter ( 6052): <asynchronous suspension>
I/flutter ( 6052): #3      RefreshIndicatorState._show.<anonymous closure>.<anonymous closure> (package:flutter/src/material/refresh_indicator.dart:579:40)
I/flutter ( 6052): <asynchronous suspension>

Description

This looks like the same root cause class as #46 (non-flat enum offset accounting), but in a different call path.

listUnspent() decodes List<LocalOutput>, and LocalOutput includes chainPosition: ChainPosition. If ChainPosition reports absolute byte offsets instead of relative bytes consumed, sequence offset accounting drifts. A later LocalOutput decode can then hand a truncated buffer to Script.read, which calls getInt64(0) (needs 8 bytes), producing the byteOffset ... : 7 error when only ~1 byte remains.

[reez]

See related isssue/PR I opened up in uniffi-dart:

• Issue: UnexpectedEnumCase in decoding Uniffi-Dart/uniffi-dart#107
• PR: Fix UnexpectedEnumCase in decoding Uniffi-Dart/uniffi-dart#108

[reez]

@OpenOne2925 did you hit this on main branch or on the issue-46 branch?

[OpenOne2925]

@OpenOne2925 did you hit this on main branch or on the issue-46 branch?

I got that error on the main branch.

[reez]

@OpenOne2925 did you hit this on main branch or on the issue-46 branch?

I got that error on the main branch.

ok that's what I was assuming, thanks for letting me know for sure. As a temporary workaround I have that patch branch #47 and I think if you point bdk_dart to that issue-46 branch in your pubspec.yaml and rebuild it should get you past this class of errors until the upstream uniffi-dart fix lands?

[reez]

@OpenOne2925 Could you update to the latest bdk-dart main and retest?

The upstream fix merged in uniffi-dart: Uniffi-Dart/uniffi-dart#108

And bdk-dart now includes it: #50

Can you confirm whether this resolves both #46 and #49 for you? If yes then I’ll close those bdk-dart issues (and the related upstream uniffi-dart tracking issue).

[OpenOne2925]

Sorry for the delayed response.
I just tried testing on the main branch, but I'm still getting the same problem.

[reez]

Sorry for the delayed response. I just tried testing on the main branch, but I'm still getting the same problem.

#46 (comment) we will see what happens here because its related

[reez]

#46 (comment)