Concurrently using std::regex, defined behaviour?

Question

Is it possible to use a std::regex object in multiple threads all using std::sregex_iterator, std::regex_match, etc.?

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Answer 1

Yes, a const std::regex is thread-safe. Actually any const method in the standard library is thread-safe, see:

§17.6.5.9/3. A C++ standard library function shall not directly or indirectly modify objects (1.10) accessible by threads other than the current thread unless the objects are accessed directly or indirectly via the function’s non-const arguments, including this.