[flang][runtime] Terminate last partial record after non-advancing write

[klausler]

After a non-advancing WRITE to a unit, ensure that any ENDFILE operation (explicit or implicit) terminates the record. (All other Fortran implementations do so except XLF.)

Fixes llvm-test-suite/Fortran/gfortran/regression/advance_6.f90.

[llvmbot]

@llvm/pr-subscribers-flang-runtime

Author: Peter Klausler (klausler)

Changes

After a non-advancing WRITE to a unit, ensure that any ENDFILE operation (explicit or implicit) terminates the record. (All other Fortran implementations do so except XLF.)

Fixes llvm-test-suite/Fortran/gfortran/regression/advance_6.f90.

---

Full diff: https://github.com/llvm/llvm-project/pull/74524.diff

1 Files Affected:

• (modified) flang/runtime/unit.cpp (+2-7)

diff --git a/flang/runtime/unit.cpp b/flang/runtime/unit.cpp
index 995656b9480c4..3895eb5c40894 100644
--- a/flang/runtime/unit.cpp
+++ b/flang/runtime/unit.cpp
@@ -591,9 +591,6 @@ void ExternalFileUnit::BackspaceRecord(IoErrorHandler &handler) {
     if (IsAfterEndfile()) {
       // BACKSPACE after explicit ENDFILE
       currentRecordNumber = *endfileRecordNumber;
-    } else if (leftTabLimit) {
-      // BACKSPACE after non-advancing I/O
-      leftTabLimit.reset();
     } else {
       DoImpliedEndfile(handler);
       if (frameOffsetInFile_ + recordOffsetInFrame_ > 0) {
@@ -910,10 +907,8 @@ void ExternalFileUnit::DoEndfile(IoErrorHandler &handler) {
   if (IsRecordFile() && access != Access::Direct) {
     furthestPositionInRecord =
         std::max(positionInRecord, furthestPositionInRecord);
-    if (leftTabLimit) {
-      // Last read/write was non-advancing, so AdvanceRecord() was not called.
-      leftTabLimit.reset();
-      ++currentRecordNumber;
+    if (direction_ == Direction::Output && leftTabLimit) {
+      AdvanceRecord(handler); // last write was non-advancing
     }
     endfileRecordNumber = currentRecordNumber;
   }