[flang][runtime] Fix runtime crash after bad recoverable OPEN (#111454)

When an OPEN statement with a unit number fails in a recoverable manner,
the runtime needs to delete the ExternalFileUnit instance that was
created in the unit map. And we do this too soon -- that instance still
holds some of the I/O statement state that will be used by a later call
into the runtime for EndIoStatement.

Move the code that deletes the unit after a failed but recoverable OPEN
into ExternalIoStatementBase::EndIoStatement, and don't do things
afterwards that would need the I/O statement state that has been
destroyed.

Fixes #111404.

flang/runtime/io-stmt.cpp

@@ -243,7 +243,15 @@ int ExternalIoStatementBase::EndIoStatement() {
   CompleteOperation();
   auto result{IoStatementBase::EndIoStatement()};
 #if !defined(RT_USE_PSEUDO_FILE_UNIT)
+  auto unitNumber{unit_.unitNumber()};
   unit_.EndIoStatement(); // annihilates *this in unit_.u_
+  if (destroy_) {
+    if (ExternalFileUnit *
+        toClose{ExternalFileUnit::LookUpForClose(unitNumber)}) {
+      toClose->Close(CloseStatus::Delete, *this);
+      toClose->DestroyClosed();
+    }
+  }
 #else
   // Fetch the unit pointer before *this disappears.
   ExternalFileUnit *unitPtr{&unit_};
@@ -329,11 +337,7 @@ void OpenStatementState::CompleteOperation() {
   }
   if (!wasExtant_ && InError()) {
     // Release the new unit on failure
-    if (ExternalFileUnit *
-        toClose{unit().LookUpForClose(unit().unitNumber())}) {
-      toClose->Close(CloseStatus::Delete, *this);
-      toClose->DestroyClosed();
-    }
+    set_destroy();
   }
   IoStatementBase::CompleteOperation();
 }

flang/runtime/io-stmt.h

@@ -455,6 +455,7 @@ class ExternalIoStatementBase : public IoStatementBase {
   RT_API_ATTRS MutableModes &mutableModes();
   RT_API_ATTRS ConnectionState &GetConnectionState();
   RT_API_ATTRS int asynchronousID() const { return asynchronousID_; }
+  RT_API_ATTRS void set_destroy(bool yes = true) { destroy_ = yes; }
   RT_API_ATTRS int EndIoStatement();
   RT_API_ATTRS ExternalFileUnit *GetExternalFileUnit() const { return &unit_; }
   RT_API_ATTRS void SetAsynchronous();
@@ -463,6 +464,7 @@ class ExternalIoStatementBase : public IoStatementBase {
 private:
   ExternalFileUnit &unit_;
   int asynchronousID_{-1};
+  bool destroy_{false};
 };
 
 template <Direction DIR>