It's quite astonishing how the historical inability of commonly used programming languages (from FORTRAN all the way to, say, Java/C#) to ergonomically return two values from a function call has caused people to invent all kinds of insane APIs/contracts.

    [double x, errno_t errno] = strtod(s, nullptr);
    if (errno != 0) {
        // ...
    }

    [x, _] = strtod(s, nullptr);  // When you're certain the error is impossible or just don't care

Instead, we're stuck with "check if the return value is -1 and if it is, check the global variable errno" at best, and with "the function doesn't really reliably reports its errors so don't feed it malformed data, idc" at worst.