Converting numbers to strings

Consider the following declarations:

    std::ostringstream oss;
    std::string str;
    char buffer[100];
    int intvalue = 42;
    float floatvalue = 3.14;
    std::to_chars_result r;

To convert the intvalue integer to a string of digits, C++17 offers us the following options:

    snprintf(buffer, sizeof buffer, "%d", intvalue);
      // available in <stdio.h>
      // locale-independent (%d is unaffected by locales)
      // non-allocating
      // bases 8, 10, 16 only

    oss << intvalue;
    str = oss.str();
      // available in <sstream>
      // locale-problematic (thousands separator may be inserted)
      // allocating; allocator-aware
      // bases 8, 10, 16 only

    str = std::to_string(intvalue);
      // available since C++11 in <string>
      // locale-independent (equivalent to %d)
      // allocating; NOT allocator-aware
      // base 10 only

    r = std::to_chars(buffer, std::end(buffer), intvalue, 10);
    *r.ptr...