[pedrobtz]

When a file does not end with ARROW1, ArrowIpcDecoderPeekFooter() reports "Expected file to end with ARROW1 but got %s" with data_end, which points one byte past the end of the input. The input is not NUL-terminated, so %s reads past the buffer until it finds a zero byte. The message now prints the six bytes that were compared, with %.6s on magic.

The existing NanoarrowIpcFooterDecodingErrors case passes a string literal, which happens to have a NUL just past its end, so it never showed the over-read. The new case copies the same ten bytes into a heap buffer of exactly that size and checks the message. Without the fix, ASan reports a heap-buffer-overflow there.

Found by fuzzing the IPC reader in the zuarrow R package, which vendors nanoarrow.

ctest passes with ASan and UBSan (409 tests). The changed files are formatted with the pinned clang-format 16.0.6.

🤖 Generated with Claude Code

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.52%. Comparing base (08d23f6) to head (f64efa9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #985   +/-   ##
=======================================
  Coverage   78.52%   78.52%           
=======================================
  Files         106      106           
  Lines       17195    17195           
  Branches     2064     2064           
=======================================
  Hits        13502    13502           
  Misses       2431     2431           
  Partials     1262     1262           

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