[GitHub] [arrow] felipecrv commented on issue #36708: `run_end_encode` segfaults on chunked arrays.

["felipecrv (via GitHub)" <gi...@apache.org>]

felipecrv commented on issue #36708:
URL: https://github.com/apache/arrow/issues/36708#issuecomment-1639118127

   Chunked arrays are handled by the kernel and even part of the unit tests, but the repro code above does indeed trigger the SIGSEGV.
   
   I isolated the cause of the SIGSEGV to some expectations in the allocation code not being preserved.
   
   ```cpp
   Result<std::shared_ptr<ArrayData>> PreallocateValuesArray(
       const std::shared_ptr<DataType>& value_type, bool has_validity_buffer, int64_t length,
       int64_t null_count, MemoryPool* pool, int64_t data_buffer_size) {
     std::vector<std::shared_ptr<Buffer>> values_data_buffers;
     std::shared_ptr<Buffer> validity_buffer = NULLPTR;
     if (has_validity_buffer) {
       ARROW_ASSIGN_OR_RAISE(validity_buffer, AllocateEmptyBitmap(length, pool));
       DCHECK(validity_buffer);
     }
     ARROW_ASSIGN_OR_RAISE(auto values_buffer, AllocateValuesBuffer(length, *value_type,
                                                                    pool, data_buffer_size));
     if (is_base_binary_like(value_type->id())) {
       const int offset_byte_width = offset_bit_width(value_type->id()) / 8;
       ARROW_ASSIGN_OR_RAISE(auto offsets_buffer,
                             AllocateBuffer((length + 1) * offset_byte_width, pool));
       // Ensure the first offset is zero
       memset(offsets_buffer->mutable_data(), 0, offset_byte_width);
       offsets_buffer->ZeroPadding();
       values_data_buffers = {validity_buffer, std::move(offsets_buffer),
                              std::move(values_buffer)};
     } else {
       values_data_buffers = {validity_buffer, std::move(values_buffer)};
     }
     auto data = ArrayData::Make(value_type, length, values_data_buffers, null_count);
     DCHECK(!has_validity_buffer || validity_buffer.use_count() == 2);
     DCHECK(!has_validity_buffer || validity_buffer != NULLPTR);
     DCHECK(!has_validity_buffer || data->buffers[0] != NULLPTR);
     return data;
   }
   ```
   
   `DCHECK(!has_validity_buffer || data->buffers[0] != NULLPTR);` fails after all the previous checks pass and I still don't understand why.
   
   
   


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