Formatting chrono duration with unsigned count triggers -Wsign-compare

[pgroke-dt]

Formatting a chrono duration with an unsigned count type triggers -Wsign-compare.

The culprit is the to_nonnegative_int function for integers:

// Converts value to int and checks that it's in the range [0, upper).
template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
inline int to_nonnegative_int(T value, int upper) {
  FMT_ASSERT(value >= 0 && value <= upper, "invalid value");
  (void)upper;
  return static_cast<int>(value);
}

Changing the assert to e.g. FMT_ASSERT(value >= 0 && value <= T{} + upper, "invalid value"); should fix this.

Also note that the implementation doesn't assert what the comment says. The comment says upper) (=exclusive) but the implementation checks for <= upper (inclusive). (The same is also true for the implementation for floating point types BTW.)
Changing this would however also require changing the line

    time.tm_hour = to_nonnegative_int(hour12(), 12);

in chrono_formatter::on_12_hour since 12 is actually a possible value there.

[vitaut]

Could you submit a PR?

[vitaut]

Suppressed in 8f426c1.