[BUG] StackOverflowError in HeadingProcessor.setHeadings on PDFs with nested list structures

[juechen703]

Bug Description

When converting certain Chinese annual report PDFs (Wuliangye 000858) to markdown or JSON format, HeadingProcessor.setHeadings enters an infinite
recursion causing a StackOverflowError.

Root Cause (bytecode analysis):

The setHeadings method uses an Enhanced for loop over getListItems():

  for (IObject item : getListItems()) {
      if (item instanceof TableBorder) {
          setHeadings(cellContents);  // ← recursive call
      }
  }

Each iteration calls addTextNode() on the list's children. Since the Enhanced for loop calls getListItems() on every iteration (not pre-fetched), it
sees the growing list and never terminates.

Affected pages: Pages with deeply nested list structures (e.g., shareholder/equity structure diagrams in Chinese annual reports).

Steps to Reproduce

1. Install: pip install opendataloader-pdf==2.2.1
2. Run:

  opendataloader-pdf 000858.SH-2016-annual.pdf -f markdown -o output --pages 33

Expected: Page 33 extracted successfully
Actual: java.lang.StackOverflowError at HeadingProcessor.setHeadings(HeadingProcessor.java:182)

Second sample: Page 34 of 000858.SH-2017-annual.pdf triggers the same bug.

Error Traceback

  java.lang.StackOverflowError
      at org.opendataloader.pdf.processors.HeadingProcessor.setHeadings(HeadingProcessor.java:171)
      at org.opendataloader.pdf.processors.HeadingProcessor.setHeadings(HeadingProcessor.java:182)  ← infinite recursion
      ... (repeats until stack overflow)

Version

• opendataloader-pdf: 2.2.1
• JAR: opendataloader-pdf-cli.jar (23MB, built 2026-04-03)

Java Version

  openjdk 17.0.18 2026-01-20
  OpenJDK Runtime Environment (build 17.0.18+8-Ubuntu-124.04.1)

Suggested Fix

  // Before (buggy):
  for (IObject item : getListItems()) { ... }

  // After (fixed):
  List<IObject> items = new ArrayList<>(getListItems());
  for (IObject item : items) { ... }

Workaround

Using -f text format bypasses HeadingProcessor and extracts successfully.

Attachments

• 000858.SH-2016-annual.pdf
  000858.SH-2016-annual.pdf
  Wuliangye 2016 annual report (page 33 triggers bug)
• 000858.SH-2017-annual.pdf
  000858.SH-2017-annual.pdf
  Wuliangye 2017 annual report (page 34 triggers bug)