[Boost-users] Difference in regex_replace replacement format handling between Boost.Regex and std::regex

There is a difference in how the replacement format string is handled by regex_replace in Boost.Regex and std::regex. Consider the following example: #include <iostream>#include <regex>#include int main() { std::string s{"a:b:c"}; std::string rx{":"}; std::string r{"\\$&"}; // Using std::regex std::string result_std = std::regex_replace(s, std::regex(rx), r); std::cout << "std::regex result: " << result_std << std::endl; // Outputs "a\:b\:c" // Using Boost.Regex std::string result_boost = boost::regex_replace(s, boost::regex(rx), r); std::cout << "Boost.Regex result: " << result_boost << std::endl; // Outputs "a$&b$&c" return 0; } std::regex result: a\:b\:c Boost.Regex result: a$&b$&c Affects Boost.Regex 1.84. I didn’t try other versions. Tested with GCC 13.2, clang 18.10 , cl 19.39.33523 and results are the same. Not tested with other versions. https://github.com/boostorg/regex/issues/210