[flang-commits] [PATCH] D125057: [flang][runtime] BACKSPACE after non-advancing I/O

[Peter Klausler via Phabricator via flang-commits]

klausler created this revision.
klausler added a reviewer: vdonaldson.
klausler added a project: Flang.
Herald added a subscriber: jdoerfert.
Herald added a project: All.
klausler requested review of this revision.

A BACKSPACE statement on a unit after a READ or WRITE with ADVANCE="NO"
must reset the position to the beginning of the record, not to the
beginning of the previous one.


https://reviews.llvm.org/D125057

Files:
  flang/runtime/io-stmt.cpp
  flang/runtime/unit.cpp


Index: flang/runtime/unit.cpp
===================================================================
--- flang/runtime/unit.cpp
+++ flang/runtime/unit.cpp
@@ -569,6 +569,9 @@
     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) {
Index: flang/runtime/io-stmt.cpp
===================================================================
--- flang/runtime/io-stmt.cpp
+++ flang/runtime/io-stmt.cpp
@@ -315,6 +315,9 @@
   }
   if constexpr (DIR == Direction::Input) {
     BeginReadingRecord(); // in case there were no I/O items
+    if (mutableModes().nonAdvancing) {
+      unit().leftTabLimit = unit().furthestPositionInRecord;
+    }
     if (!mutableModes().nonAdvancing || GetIoStat() == IostatEor) {
       FinishReadingRecord();
     }


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