Bug #19043
open
Segfault on macOS 11.7 while using StringScanner in multiple threads
Description
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.
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