GH-50149: [C++][Parquet] Handle OOM as soft failure in parquet encoding fuzzer

[omertt27]

Rationale for this change

When the CappedMemoryPool (2.2 GB limit, added in GH-48105) triggers an OOM during encoding roundtrip verification, the resulting Status::OutOfMemory propagates back to call sites that used ARROW_CHECK_OK(...) or .ValueOrDie(). Both of these expand to ARROW_LOG(FATAL) → std::abort(), which is not an exception — BEGIN_PARQUET_CATCH_EXCEPTIONS cannot intercept it. OSS-Fuzz then sees a process crash instead of a resource-limit event.

What changes are included in this PR?

Added FuzzCheckOk(Status) in the anonymous namespace of fuzz_encoding_internal.cc:

// OOM during fuzzing is an expected soft failure; any other non-OK status
// indicates a real bug and should abort so OSS-Fuzz can report it.
Status FuzzCheckOk(const Status& st) {
  if (st.IsOutOfMemory()) return st;
  ARROW_CHECK_OK(st);
  return Status::OK();
}

Six call sites in TypedFuzzEncoding::Fuzz() replaced with RETURN_NOT_OK(FuzzCheckOk(...)):

• reference_array_->ValidateFull()
• DecodeArrow(...).ValueOrDie() (replaced with status check + std::move(*result))
• array->ValidateFull() (on roundtrip result)
• CompareAgainstReference(array)
• RunOnDecodedChunks(...) × 2 (both arrow_supported() and non-Arrow branches)

Three invariant checks intentionally left as hard aborts — they indicate actual decoder/encoder bugs, not resource limits:

• ARROW_CHECK_LE(values_read, read_size) — decoder returning more values than requested
• ARROW_CHECK_EQ(acc.chunks.size(), 0) — BinaryBuilder invariant
• ARROW_CHECK_EQ(offset, total_data_size) — byte count invariant in MakeArrow

Are these changes tested?

The OOM path is exercised by fuzzing_memory_pool() in fuzz_internal.cc whenever the cumulative allocation exceeds the 2.2 GB cap. The existing parquet-encoding-test suite covers the non-OOM code paths.

Closes #50149

• GitHub Issue: [C++][Parquet] OOM leads to hard failure in parquet-encoding-fuzz #50149

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds fuzzing-specific status handling to treat OutOfMemory as a non-fatal outcome while ensuring all other non-OK statuses abort, improving OSS-Fuzz signal quality.

Changes:

• Introduce FuzzCheckOk helper to allow OOM to bubble up while aborting on other failures.
• Replace several ARROW_CHECK_OK / ValueOrDie() call sites with RETURN_NOT_OK(FuzzCheckOk(...)) to avoid hard aborts on OOM.
• Propagate OOM through decoding/validation/compare and chunked decoding paths.

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[pitrou]

Closing this PR as it's superseded by #50150