Encountering SIGSEGV when parsing multiple rule sets in parallel

Describe the bug

Hello!

I'm encountering an error when creating multiple rule sets and adding rules to each of them in a multi-threaded environment.

Logs and dumps

I've traced it back to yylex in yy::seclang_parser::parse():

#0  0x00007bb94eea02d8 in yylex(modsecurity::Parser::Driver&) ()
   from /usr/lib/libmodsecurity.so.3
#1  0x00007bb94ee78c0e in yy::seclang_parser::parse() ()
   from /usr/lib/libmodsecurity.so.3
#2  0x00007bb94eeba170 in modsecurity::Parser::Driver::parse(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
   from /usr/lib/libmodsecurity.so.3
#3  0x00007bb94eeba4a6 in modsecurity::Parser::Driver::parseFile(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) ()
   from /usr/lib/libmodsecurity.so.3
#4  0x00007bb94eed0a17 in modsecurity::RulesSet::loadFromUri(char const*) ()
   from /usr/lib/libmodsecurity.so.3
#5  0x00007bb94eed0b68 in msc_rules_add_file ()
   from /usr/lib/libmodsecurity.so.3

...(omitted for brevity)

Is this a known issue? Is Rules meant to be initialized and filled only once and in a single-threaded context?

Start with modsecurity::RulesSet::loadFromUri and msc_rules_add_file, then trace the call path through Parser::Driver::parseFile, parse, and yylex. Reproduce parallel rule-set loading and establish whether these entry points are safe to use concurrently; done means the SIGSEGV cause and supported initialization behavior are identified and covered by an appropriate regression check.