[flang-commits] [flang] [flang][runtime] Clear leftTabLimit at in FinishReadingRecord (PR #98822)

[Peter Klausler via flang-commits]

https://github.com/klausler created https://github.com/llvm/llvm-project/pull/98822

ExternalFileUnit::FinishReadingRecord() is called at the end of a READ statement, unless the read is non-advancing and there was no error.  In the event of an erroneous non-advancing read, however, FinishReadingRecord() leaves ConnectionState::leftTabLimit inhabited by a value, leaving the impression that the *next* record is undergoing a non-advancing operation, and this cause the next operation to fail.  In the test case in the reported bug, the next operation is a BACKSPACE, and it ends up doing nothing.  The fix is to always reset leftTabLimit in FinishReadingRecord.

Fixes https://github.com/llvm/llvm-project/issues/98783.

>From f317c757076204af3d36d7d9c8bba6b8990d8cc1 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Sun, 14 Jul 2024 09:23:12 -0700
Subject: [PATCH] [flang][runtime] Clear leftTabLimit at in FinishReadingRecord

ExternalFileUnit::FinishReadingRecord() is called at the end of
a READ statement, unless the read is non-advancing and there was
no error.  In the event of an erroneous non-advancing read,
however, FinishReadingRecord() leaves ConnectionState::leftTabLimit
inhabited by a value, leaving the impression that the *next*
record is undergoing a non-advancing operation, and this cause
the next operation to fail.  In the test case in the reported
bug, the next operation is a BACKSPACE, and it ends up doing
nothing.  The fix is to always reset leftTabLimit in
FinishReadingRecord.

Fixes https://github.com/llvm/llvm-project/issues/98783.
---
 flang/runtime/unit.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/flang/runtime/unit.cpp b/flang/runtime/unit.cpp
index a11f444d8d754..5c5bca835f3d8 100644
--- a/flang/runtime/unit.cpp
+++ b/flang/runtime/unit.cpp
@@ -268,6 +268,7 @@ void ExternalFileUnit::FinishReadingRecord(IoErrorHandler &handler) {
     recordOffsetInFrame_ = 0;
   }
   BeginRecord();
+  leftTabLimit.reset();
 }
 
 bool ExternalFileUnit::AdvanceRecord(IoErrorHandler &handler) {