[flang][runtime] Catch input error case of missing integer value

Formatted input allows for an empty numeric input field, which
signifies a zero value, but list-directed and NAMELIST input does
not -- apart from the special case of a NAMELIST array.

Differential Revision: https://reviews.llvm.org/D132178

Author: klausler

flang/runtime/edit-input.cpp

@@ -118,7 +118,7 @@ bool EditIntegerInput(
   RUNTIME_CHECK(io.GetIoErrorHandler(), kind >= 1 && !(kind & (kind - 1)));
   switch (edit.descriptor) {
   case DataEdit::ListDirected:
-    if (IsNamelistName(io)) {
+    if (IsNamelistNameOrSlash(io)) {
       return false;
     }
     break;
@@ -172,6 +172,11 @@ bool EditIntegerInput(
     value += digit;
     any = true;
   }
+  if (!any && !remaining) {
+    io.GetIoErrorHandler().SignalError(
+        "Integer value absent from NAMELIST or list-directed input");
+    return false;
+  }
   auto maxForKind{common::UnsignedInt128{1} << ((8 * kind) - 1)};
   overflow |= value >= maxForKind && (value > maxForKind || !negate);
   if (overflow) {
@@ -527,7 +532,7 @@ template <int KIND>
 bool EditRealInput(IoStatementState &io, const DataEdit &edit, void *n) {
   switch (edit.descriptor) {
   case DataEdit::ListDirected:
-    if (IsNamelistName(io)) {
+    if (IsNamelistNameOrSlash(io)) {
       return false;
     }
     return EditCommonRealInput<KIND>(io, edit, n);
@@ -561,7 +566,7 @@ bool EditRealInput(IoStatementState &io, const DataEdit &edit, void *n) {
 bool EditLogicalInput(IoStatementState &io, const DataEdit &edit, bool &x) {
   switch (edit.descriptor) {
   case DataEdit::ListDirected:
-    if (IsNamelistName(io)) {
+    if (IsNamelistNameOrSlash(io)) {
       return false;
     }
     break;
@@ -650,7 +655,7 @@ static bool EditListDirectedCharacterInput(
     io.HandleRelativePosition(byteCount);
     return EditDelimitedCharacterInput(io, x, length, *ch);
   }
-  if (IsNamelistName(io) || io.GetConnectionState().IsAtEOF()) {
+  if (IsNamelistNameOrSlash(io) || io.GetConnectionState().IsAtEOF()) {
     return false;
   }
   // Undelimited list-directed character input: stop at a value separator

flang/runtime/namelist.cpp

@@ -493,7 +493,7 @@ bool IONAME(InputNamelist)(Cookie cookie, const NamelistGroup &group) {
   return true;
 }
 
-bool IsNamelistName(IoStatementState &io) {
+bool IsNamelistNameOrSlash(IoStatementState &io) {
   if (auto *listInput{
           io.get_if<ListDirectedStatementState<Direction::Input>>()}) {
     if (listInput->inNamelistArray()) {
@@ -508,6 +508,8 @@ bool IsNamelistName(IoStatementState &io) {
           ch = io.GetNextNonBlank(byteCount);
           // TODO: how to deal with NaN(...) ambiguity?
           return ch && (*ch == '=' || *ch == '(' || *ch == '%');
+        } else {
+          return *ch == '/';
         }
       }
     }

flang/runtime/namelist.h

@@ -35,10 +35,11 @@ class NamelistGroup {
   const Item *item; // in original declaration order
 };
 
-// Look ahead on input for an identifier followed by a '=', '(', or '%'
+// Look ahead on input for a '/' or an identifier followed by a '=', '(', or '%'
 // character; for use in disambiguating a name-like value (e.g. F or T) from a
-// NAMELIST group item name.  Always false when not reading a NAMELIST.
-bool IsNamelistName(IoStatementState &);
+// NAMELIST group item name and for coping with short arrays.  Always false
+// when not reading a NAMELIST.
+bool IsNamelistNameOrSlash(IoStatementState &);
 
 } // namespace Fortran::runtime::io
 #endif // FORTRAN_RUNTIME_NAMELIST_H_