ref: Record that Android assembly store v4 never shipped

[jamescrosswell]

Stacked on #5577 — this PR's diff is only the comment/attribution corrections and one added test case.

Closes #5604

Summary

#5604 flagged a new commit under the upstream code we vendor into src/Sentry.Android.AssemblyReader/: 8f7c4d4, "[CoreCLR] Remove assembly store decompression cache" (dotnet/android#12780). Reviewing it: it does affect us, and in our favour.

Upstream remeasured the opt-in decompression cache and found it made startup worse (+162 ms TTID, +179 ms TTFD), so they removed it — and with it the content_id header field it needed, restoring assembly store format version 3 for both CoreCLR and MonoVM. Verified on dotnet/android main:

• AssemblyStoreGenerator.cs emits ASSEMBLY_STORE_FORMAT_VERSION_CORECLR_64BIT = 0x80000003
• StoreReader_V2.Classes.cs has no content_id; Header.NativeSize is a flat 5 * sizeof(uint) const
• StoreReader_V2.cs no longer lists the _V4 | ABI versions, and has dropped ASSEMBLY_STORE_FORMAT_NUMBER_MASK

main is the .NET 11 branch — there is no release/11.0.1xx, and eng/Versions.props carries AndroidPackVersion 37.2.0 with suffix rc.2. The revert (2026-09-15) predates rc.2, while our global.json pins 11.0.100-rc.1 / workload 11.0.100-rc.1.26458.5 (2026-09-08), the last build that emitted v4. So v4 never shipped, and .NET 11 GA will emit v3.

What this means for the stack

• feat: Accept Android assembly store v4 versions #5574 (v4 versions) — now dead code. Harmless: a v4-aware reader reads v3 correctly either way. Removal is tracked by ref: Remove Android assembly store v4 support (never shipped) #5608, deliberately deferred until the SDK pin moves off rc.1 so the net11.0 APK tests are exercising real v3 stores when it happens.
• feat: Support Zstandard-compressed assemblies on Android (.NET 11) #5575 (Zstandard) — unaffected. The revert removed the decompression cache, not Zstd compression; AssemblyCompression.cs upstream still has the XAZS magic.
• feat: Support reading .NET 11 Android assembly stores #5577 (index entry sizing) — load-bearing. With v4 gone, the index entry size is the only thing that distinguishes a CoreCLR store from a MonoVM one: CoreCLR still writes 32-bit CRC32 name hashes on every ABI, so a .NET 11 GA arm64 store is v3, 64-bit ABI, 9-byte index entries. The pre-feat: Support reading .NET 11 Android assembly stores #5577 reader picks the hash width off the ABI bit and would read 8 bytes where there are 4. feat: Support reading .NET 11 Android assembly stores #5577 derives it from index_size / index_entry_count, which is what upstream kept through the revert.

Changes

• File headers in StoreReader.cs / StoreReader.Classes.cs and V2/ATTRIBUTION.txt said v4 "ships in .NET 11". It doesn't — they now say previews only, and record the revert as a sync point.
• The // Must match the ASSEMBLY_STORE_FORMAT_VERSION native constant note on the v4 constant is stale; no native constant has that value any more.
• StoreReaderTests had a synthetic v4 64-bit store with 32-bit hashes but no v3 equivalent — i.e. no coverage of the shape .NET 11 GA will actually produce. Added.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.80%. Comparing base (8877577) to head (a4f9683).
⚠️ Report is 4 commits behind head on feat/assemblystore-index-sizing.

Additional details and impacted files

@@                         Coverage Diff                         @@
##           feat/assemblystore-index-sizing    #5609      +/-   ##
===================================================================
- Coverage                            74.90%   74.80%   -0.11%     
===================================================================
  Files                                  515      515              
  Lines                                18916    18916              
  Branches                              3693     3693              
===================================================================
- Hits                                 14169    14150      -19     
- Misses                                3872     3890      +18     
- Partials                               875      876       +1     

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