[GitHub] [arrow] Yuhta commented on a change in pull request #8937: ARROW-10932: [C++] BinaryMemoTable::CopyOffsets access out-of-bound address when data is empty

[GitBox <gi...@apache.org>]

Yuhta commented on a change in pull request #8937:
URL: https://github.com/apache/arrow/pull/8937#discussion_r544500867



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File path: cpp/src/arrow/util/hashing.h
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@@ -691,7 +691,7 @@ class BinaryMemoTable : public MemoTable {
 
     const builder_offset_type* offsets = binary_builder_.offsets_data();
     const builder_offset_type delta =
-        start < binary_builder_.value_data_length() ? offsets[start] : 0;
+        start < binary_builder_.length() ? offsets[start] : 0;

Review comment:
       `binary_builder_.length() != 0` is the minimal case we need to fix, and we still do out-of-bound access (and write the data read to `out_data`) when `start >= binary_builder_.length()`.
   If we do `start < binary_builder_.length()`, we cover the case when `start >= binary_builder_.length()` as well.




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