Fixes found by fuzzer:
OnDiskTrieRawHashMap:
- Bounds-check data slot offsets in TrieVerifier::visitSlot() before
calling getRecord(), preventing asData() assertion on out-of-bounds
trie entries.
- Validate subtrie headers (NumBits, bounds) before constructing
SubtrieHandle, preventing SEGV in getSlots() from corrupt NumBits.
- Validate arena bump pointer alignment, catching misaligned BumpPtr
that would crash store() with an alignment assertion.
- Fix comma operator bug in getOrCreateRoot() where the
compare_exchange_strong result was discarded, causing asSubtrie()
assertion when RootTrieOffset was corrupted to zero.
OnDiskGraphDB:
- Reject invalid (zero) ref offsets in validate callback, preventing
asData() assertion when corrupt data pool refs are resolved via
recoverFromFileOffset().
- Validate DataRecordHandle layout flags before calling getTotalSize(),
preventing llvm_unreachable on corrupt NumRefsFlags/DataSizeFlags.
- Validate data pool bump pointer alignment, catching misaligned
BumpPtr that would crash store() in DataRecordHandle::constructImpl().
- Check data record refs offset alignment before calling getRefs(),
preventing PointerUnion assertion from misaligned refs pointer.
MappedFileRegionArena:
- Convert assertions in initializeHeader() to errors so corrupted
arena headers return an error on CAS open instead of crashing.
Assisted-By: Claude
1a0ca1019d