[ARROW-7985] [C++] ListBuilder.Finish fails if underlying value builder is empty and .Reserve'd

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.15.1
• Fix Version/s: 0.17.0
• Component/s: C++
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/24203
• Assignee: Antoine Pitrou
• Reporter: John Jenkins
• Created: 02/Mar/20 19:02
• Updated: 11/Jan/23 07:57
• Resolved: 12/Mar/20 21:13

Description

Here's a reproduction:

#include <arrow/builder.h>
#include <arrow/status.h>
#include <iostream>

int main() {
        arrow::ListBuilder lb(arrow::default_memory_pool(), std::unique_ptr<arrow::ArrayBuilder>(new arrow::Int32Builder()));
        lb.value_builder()->Reserve(100); // bug
        lb.Append();
        std::shared_ptr<arrow::Array> ar;
        arrow::Status st = lb.Finish(&ar);
        if (!st.ok()) {
                std::cerr << st << '\n';
                return 1;
        }
}

The output is

Invalid: Resize cannot downsize

The Resize call is made at builder_nested.h, line 115. There's a note there about ARROW-2744. Perhaps the fix is to look at capacity rather than length?

Issue Links

• links to: GitHub Pull Request #6595