[flang][runtime] Signal new I/O error on floating-point input overflow

[klausler]

Summary

Besides raising the IEEE floating-point overflow exception, treat
a floating-point overflow on input as an I/O error catchable with
ERR=, IOSTAT=, &/or IOMSG=.

flang/include/flang/Runtime/iostat.h

enum Iostat {
   IostatUTF8Decoding,
   IostatUnitOverflow,
   IostatBadRealInput,
   IostatBadScaleFactor,
   IostatBadAsynchronous,
   IostatBadWaitUnit,
   IostatBOZInputOverflow,
   IostatIntegerInputOverflow,
+  IostatRealInputOverflow,
 };
 
 const char *IostatErrorString(int);
 
 } // namespace Fortran::runtime::io
 #endif // FORTRAN_RUNTIME_IOSTAT_H_

flang/runtime/edit-input.cpp

if (edit.width && p < str + *edit.width) {
     return false; // unconverted characters remain in fixed width field
   }
   // Success on the fast path!
   *reinterpret_cast<decimal::BinaryFloatingPointNumber<PRECISION> *>(n) =
       converted.binary;
   io.HandleRelativePosition(p - str);
   // Set FP exception flags
   if (converted.flags != decimal::ConversionResultFlags::Exact) {
+    if (converted.flags & decimal::ConversionResultFlags::Overflow) {
+      return false; // let slow path deal with it
+    }
     RaiseFPExceptions(converted.flags);
   }
   return true;
 }
 
 template <int KIND>
 bool EditCommonRealInput(IoStatementState &io, const DataEdit &edit, void *n) {
   constexpr int binaryPrecision{common::PrecisionOfRealKind(KIND)};
bool EditCommonRealInput(IoStatementState &io, const DataEdit &edit, void *n) {
   if (*p) { // unprocessed junk after value
     io.GetIoErrorHandler().SignalError(IostatBadRealInput);
     return false;
   }
   *reinterpret_cast<decimal::BinaryFloatingPointNumber<binaryPrecision> *>(n) =
       converted.binary;
   // Set FP exception flags
   if (converted.flags != decimal::ConversionResultFlags::Exact) {
+    if (converted.flags & decimal::ConversionResultFlags::Overflow) {
+      io.GetIoErrorHandler().SignalError(IostatRealInputOverflow);
+      return false;
+    }
     RaiseFPExceptions(converted.flags);
   }
   return true;
 }
 
 template <int KIND>
 bool EditRealInput(IoStatementState &io, const DataEdit &edit, void *n) {
   switch (edit.descriptor) {

flang/runtime/iostat.cpp

case IostatBadAsynchronous:
     return "READ/WRITE(ASYNCHRONOUS='YES') on unit without "
            "OPEN(ASYNCHRONOUS='YES')";
   case IostatBadWaitUnit:
     return "WAIT(ID=nonzero) for a bad unit number";
   case IostatBOZInputOverflow:
     return "B/O/Z input value overflows variable";
   case IostatIntegerInputOverflow:
     return "Integer input value overflows variable";
+  case IostatRealInputOverflow:
+    return "Real or complex input value overflows type";
   default:
     return nullptr;
   }
 }
 
 } // namespace Fortran::runtime::io