Ruby

During testing on our CI, one of the runners failed due to a segfault that appears to have originated from the StringScanner class, specifically the scan_until method. The test ensures that we are able to properly parse strings in a multithreaded environment.

 def test_multithreaded parser = RGeo::WKRep::WKTParser.new data = fixtures.join("isere.wkt").read Array.new(100) do Thread.fork do parser.parse(data) end end.map(&:join) end 

Here's the parse method

 def parse(str) @mutex.synchronize do str = str.downcase @cur_factory = @exact_factory if @cur_factory @cur_factory_support_z = @cur_factory.property(:has_z_coordinate) ? true : false @cur_factory_support_m = @cur_factory.property(:has_m_coordinate) ? true : false end @cur_expect_z = nil @cur_expect_m = nil @cur_srid = @default_srid if @support_ewkt && str =~ /^srid=(\d+);/i str = $' @cur_srid = Regexp.last_match(1).to_i end begin start_scanner(str) obj = parse_type_tag if @cur_token && !@ignore_extra_tokens raise Error::ParseError, "Extra tokens beginning with #{@cur_token.inspect}." end ensure clean_scanner end obj end end 

Where the StringScanner is created and assigned to @scanner in start_scanner and @scanner is set to nil in clean_scanner. According to the control frame information in the log, the error is caused in the scan_until method, but it might be due to gc_sweep being run at some point.

Unfortunately since this happened on a CI system I don't have access to the diagnostic file. We've tried to replicate this locally unsuccessfully. The best we've done is caused a deadlock while trying to join the threads, but cannot reliably reproduce that. Here's a link to the CI run that caused the issue if that's helpful (https://github.com/rgeo/rgeo/actions/runs/3144578897/jobs/5110771257).

If there's any tips on how to reproduce or anything you want me to try to get more information please let me know.