[flang] Detect output field width overflow for Inf/NaN

[klausler]

Summary

The output editing code paths for F and E/D output that handle
IEEE-754 infinities and NaNs fail to check for overflow of the
output field, which should cause the field to be filled with
asterisks instead. Catch these cases.

flang/runtime/edit-output.cpp

if (isEN) {
     ++significantDigits;
     scale = std::min(scale, significantDigits + 1);
   }
   // In EN editing, multiple attempts may be necessary, so this is a loop.
   while (true) {
     decimal::ConversionToDecimalResult converted{
         Convert(significantDigits, edit.modes.round, flags)};
     if (IsInfOrNaN(converted)) {
-      return EmitPrefix(edit, converted.length, editWidth) &&
-          EmitAscii(io_, converted.str, converted.length) && EmitSuffix(edit);
+      return editWidth > 0 &&
+              converted.length > static_cast<std::size_t>(editWidth)
+          ? EmitRepeated(io_, '*', editWidth)
+          : EmitPrefix(edit, converted.length, editWidth) &&
+              EmitAscii(io_, converted.str, converted.length) &&
+              EmitSuffix(edit);
     }
     if (!IsZero()) {
       converted.decimalExponent -= scale;
     }
     if (isEN) {
       // EN mode: we need an effective exponent field that is
       // a multiple of three.
       if (int modulus{converted.decimalExponent % 3}; modulus != 0) {
bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
   // Multiple conversions may be needed to get the right number of
   // effective rounded fractional digits.
   int extraDigits{0};
   bool canIncrease{true};
   while (true) {
     decimal::ConversionToDecimalResult converted{
         Convert(extraDigits + fracDigits, rounding, flags)};
     if (IsInfOrNaN(converted)) {
-      return EmitPrefix(edit, converted.length, editWidth) &&
-          EmitAscii(io_, converted.str, converted.length) && EmitSuffix(edit);
+      return editWidth > 0 &&
+              converted.length > static_cast<std::size_t>(editWidth)
+          ? EmitRepeated(io_, '*', editWidth)
+          : EmitPrefix(edit, converted.length, editWidth) &&
+              EmitAscii(io_, converted.str, converted.length) &&
+              EmitSuffix(edit);
     }
     int expo{converted.decimalExponent + edit.modes.scale /*kP*/};
     int signLength{*converted.str == '-' || *converted.str == '+' ? 1 : 0};
     int convertedDigits{static_cast<int>(converted.length) - signLength};
     if (IsZero()) { // don't treat converted "0" as significant digit
       expo = 0;
       convertedDigits = 0;
     }