[flang] Support legacy usage of 'A' edit descriptors for integer & real

[klausler]

Summary

The 'A' edit descriptor once served as a form of raw I/O of bytes
to/from variables that weren't of type CHARACTER (which itself
didn't exist until F'77). This usage was especially common for
output of numeric variables that had been initialized with Hollerith.

flang/runtime/edit-input.cpp

bool EditIntegerInput(
   case 'I':
     break;
   case 'B':
     return EditBOZInput(io, edit, n, 2, kind << 3);
   case 'O':
     return EditBOZInput(io, edit, n, 8, kind << 3);
   case 'Z':
     return EditBOZInput(io, edit, n, 16, kind << 3);
+  case 'A': // legacy extension
+    return EditDefaultCharacterInput(
+        io, edit, reinterpret_cast<char *>(n), kind);
   default:
     io.GetIoErrorHandler().SignalError(IostatErrorInFormat,
         "Data edit descriptor '%c' may not be used with an INTEGER data item",
         edit.descriptor);
     return false;
   }
   std::optional<int> remaining;
   std::optional<char32_t> next;
case 'B':
     return EditBOZInput(
         io, edit, n, 2, common::BitsForBinaryPrecision(binaryPrecision));
   case 'O':
     return EditBOZInput(
         io, edit, n, 8, common::BitsForBinaryPrecision(binaryPrecision));
   case 'Z':
     return EditBOZInput(
         io, edit, n, 16, common::BitsForBinaryPrecision(binaryPrecision));
+  case 'A': // legacy extension
+    return EditDefaultCharacterInput(
+        io, edit, reinterpret_cast<char *>(n), KIND);
   default:
     io.GetIoErrorHandler().SignalError(IostatErrorInFormat,
         "Data edit descriptor '%c' may not be used for REAL input",
         edit.descriptor);
     return false;
   }
 }
 

flang/runtime/edit-output.cpp

case 'O':
     }
     break;
   case 'Z':
     for (; un > 0; un >>= 4) {
       int digit = static_cast<int>(un) & 0xf;
       *--p = digit >= 10 ? 'A' + (digit - 10) : '0' + digit;
     }
     break;
+  case 'A': // legacy extension
+    return EditDefaultCharacterOutput(
+        io, edit, reinterpret_cast<char *>(&n), sizeof n);
   default:
     io.GetIoErrorHandler().Crash(
         "Data edit descriptor '%c' may not be used with an INTEGER data item",
         edit.descriptor);
     return false;
   }
 
   int digits = end - p;
template <int KIND> bool RealOutputEditing<KIND>::Edit(const DataEdit &edit) {
   case 'B':
   case 'O':
   case 'Z':
     return EditIntegerOutput<KIND>(io_, edit,
         static_cast<common::HostSignedIntType<8 * KIND>>(
             decimal::BinaryFloatingPointNumber<binaryPrecision>{x_}.raw()));
   case 'G':
     return Edit(EditForGOutput(edit));
+  case 'A': // legacy extension
+    return EditDefaultCharacterOutput(
+        io_, edit, reinterpret_cast<char *>(&x_), sizeof x_);
   default:
     if (edit.IsListDirected()) {
       return EditListDirectedOutput(edit);
     }
     io_.GetIoErrorHandler().SignalError(IostatErrorInFormat,
         "Data edit descriptor '%c' may not be used with a REAL data item",
         edit.descriptor);
     return false;

flang/unittests/Runtime/RuntimeCrashTest.cpp

 struct TestIOCrash : CrashHandlerFixture {};
 
 TEST(TestIOCrash, FormatDescriptorWriteMismatchTest) {
   static constexpr int bufferSize{4};
   static char buffer[bufferSize];
   static const char *format{"(A4)"};
   auto *cookie{IONAME(BeginInternalFormattedOutput)(
       buffer, bufferSize, format, std::strlen(format))};
-  ASSERT_DEATH(IONAME(OutputInteger64)(cookie, 0xfeedface),
-      "Data edit descriptor 'A' may not be used with an INTEGER data item");
+  ASSERT_DEATH(IONAME(OutputLogical)(cookie, true),
+      "Data edit descriptor 'A' may not be used with a LOGICAL data item");
 }
 
 TEST(TestIOCrash, InvalidFormatCharacterTest) {
   static constexpr int bufferSize{1};
   static char buffer[bufferSize];
   static const char *format{"(C1)"};
   auto *cookie{IONAME(BeginInternalFormattedOutput)(
       buffer, bufferSize, format, std::strlen(format))};