[flang][runtime] Allow child NAMELIST input to advance records (#153963)

NAMELIST input in child I/O is rare, and it's not clear in the standard
whether it should be allowed to advance to later records in the parent
unit. But GNU Fortran supports it, and there's no good reason not to do
so since a NAMELIST input group that isn't terminated on the same line
is otherwise going to be a fatal error.

Fixes #153416.

Author: klausler

flang-rt/include/flang-rt/runtime/io-stmt.h

@@ -696,6 +696,7 @@ class ChildListIoStatementState : public ChildIoStatementState<DIR>,
   RT_API_ATTRS ChildListIoStatementState(
       ChildIo &, const char *sourceFile = nullptr, int sourceLine = 0);
   using ListDirectedStatementState<DIR>::GetNextDataEdit;
+  RT_API_ATTRS bool AdvanceRecord(int = 1);
   RT_API_ATTRS int EndIoStatement();
 };
 

flang-rt/lib/runtime/io-stmt.cpp

@@ -1106,10 +1106,14 @@ ChildListIoStatementState<DIR>::ChildListIoStatementState(
 }
 
 template <Direction DIR>
-bool ChildUnformattedIoStatementState<DIR>::Receive(
-    char *data, std::size_t bytes, std::size_t elementBytes) {
+bool ChildListIoStatementState<DIR>::AdvanceRecord(int n) {
 #if !defined(RT_DEVICE_AVOID_RECURSION)
-  return this->child().parent().Receive(data, bytes, elementBytes);
+  // Allow child NAMELIST input to advance
+  if (DIR == Direction::Input && this->mutableModes().inNamelist) {
+    return this->child().parent().AdvanceRecord(n);
+  } else {
+    return false;
+  }
 #else
   this->ReportUnsupportedChildIo();
 #endif
@@ -1125,6 +1129,16 @@ template <Direction DIR> int ChildListIoStatementState<DIR>::EndIoStatement() {
   return ChildIoStatementState<DIR>::EndIoStatement();
 }
 
+template <Direction DIR>
+bool ChildUnformattedIoStatementState<DIR>::Receive(
+    char *data, std::size_t bytes, std::size_t elementBytes) {
+#if !defined(RT_DEVICE_AVOID_RECURSION)
+  return this->child().parent().Receive(data, bytes, elementBytes);
+#else
+  this->ReportUnsupportedChildIo();
+#endif
+}
+
 template class InternalIoStatementState<Direction::Output>;
 template class InternalIoStatementState<Direction::Input>;
 template class InternalFormattedIoStatementState<Direction::Output>;