Dan Story and ergosys provided good answers (apparently I was looking in the wrong place, that’s why the headaches) but while I’m at it I wanted to provide a copy&paste solution for the function in my question for future googlers:
#include <boost/crc.hpp>
uint32_t GetCrc32(const string& my_string) {
boost::crc_32_type result;
result.process_bytes(my_string.data(), my_string.length());
return result.checksum();
}