[flang-commits] [flang] [flang][runtime] Handle unconsumed repeated list-directed input items (PR #75400)

[Peter Klausler via flang-commits]

https://github.com/klausler created https://github.com/llvm/llvm-project/pull/75400

If list-directed input contains a repeated item ("20*123.0") that is not fully consumed by the READ statement's data item list, the end of that READ statement was repositioning the input to the repeated value ("123.0"), leading to later confusion.  Cancel the input item repetition during EndIoStatement() processing to prevent this misbehavior.

Fixes llvm-test-suite/Fortran/gfortran/regression/list_read_4.f90.

>From cf722afc2d59760146964e39b2483b65765fdb83 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Wed, 13 Dec 2023 15:05:47 -0800
Subject: [PATCH] [flang][runtime] Handle unconsumed repeated list-directed
 input items

If list-directed input contains a repeated item ("20*123.0") that
is not fully consumed by the READ statement's data item list, the
end of that READ statement was repositioning the input to the
repeated value ("123.0"), leading to later confusion.  Cancel the
input item repetition during EndIoStatement() processing to
prevent this misbehavior.

Fixes llvm-test-suite/Fortran/gfortran/regression/list_read_4.f90.
---
 flang/runtime/connection.cpp | 16 ++++++++-------
 flang/runtime/connection.h   |  2 ++
 flang/runtime/io-stmt.cpp    | 39 ++++++++++++++++++++++++++++++++++++
 flang/runtime/io-stmt.h      |  7 +++++++
 4 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/flang/runtime/connection.cpp b/flang/runtime/connection.cpp
index 0abacd7995b471..91ac9a0e14e47b 100644
--- a/flang/runtime/connection.cpp
+++ b/flang/runtime/connection.cpp
@@ -46,13 +46,15 @@ SavedPosition::SavedPosition(IoStatementState &io) : io_{io} {
 }
 
 SavedPosition::~SavedPosition() {
-  ConnectionState &conn{io_.GetConnectionState()};
-  while (conn.currentRecordNumber > saved_.currentRecordNumber) {
-    io_.BackspaceRecord();
+  if (!cancelled_) {
+    ConnectionState &conn{io_.GetConnectionState()};
+    while (conn.currentRecordNumber > saved_.currentRecordNumber) {
+      io_.BackspaceRecord();
+    }
+    conn.leftTabLimit = saved_.leftTabLimit;
+    conn.furthestPositionInRecord = saved_.furthestPositionInRecord;
+    conn.positionInRecord = saved_.positionInRecord;
+    conn.pinnedFrame = saved_.pinnedFrame;
   }
-  conn.leftTabLimit = saved_.leftTabLimit;
-  conn.furthestPositionInRecord = saved_.furthestPositionInRecord;
-  conn.positionInRecord = saved_.positionInRecord;
-  conn.pinnedFrame = saved_.pinnedFrame;
 }
 } // namespace Fortran::runtime::io
diff --git a/flang/runtime/connection.h b/flang/runtime/connection.h
index 70c20e17fd01ac..c9a7566f209881 100644
--- a/flang/runtime/connection.h
+++ b/flang/runtime/connection.h
@@ -111,10 +111,12 @@ class SavedPosition {
 public:
   explicit SavedPosition(IoStatementState &);
   ~SavedPosition();
+  void Cancel() { cancelled_ = true; }
 
 private:
   IoStatementState &io_;
   ConnectionState saved_;
+  bool cancelled_{false};
 };
 
 } // namespace Fortran::runtime::io
diff --git a/flang/runtime/io-stmt.cpp b/flang/runtime/io-stmt.cpp
index dedf1f8364ad37..fc84f1f1da953f 100644
--- a/flang/runtime/io-stmt.cpp
+++ b/flang/runtime/io-stmt.cpp
@@ -189,6 +189,17 @@ InternalListIoStatementState<DIR>::InternalListIoStatementState(
     : InternalIoStatementState<DIR>{d, sourceFile, sourceLine},
       ioStatementState_{*this} {}
 
+template <Direction DIR>
+int InternalListIoStatementState<DIR>::EndIoStatement() {
+  if constexpr (DIR == Direction::Input) {
+    if (int status{ListDirectedStatementState<DIR>::EndIoStatement()};
+        status != IostatOk) {
+      return status;
+    }
+  }
+  return InternalIoStatementState<DIR>::EndIoStatement();
+}
+
 ExternalIoStatementBase::ExternalIoStatementBase(
     ExternalFileUnit &unit, const char *sourceFile, int sourceLine)
     : IoStatementBase{sourceFile, sourceLine}, unit_{unit} {}
@@ -707,6 +718,13 @@ ListDirectedStatementState<Direction::Output>::GetNextDataEdit(
   return edit;
 }
 
+int ListDirectedStatementState<Direction::Input>::EndIoStatement() {
+  if (repeatPosition_) {
+    repeatPosition_->Cancel();
+  }
+  return IostatOk;
+}
+
 std::optional<DataEdit>
 ListDirectedStatementState<Direction::Input>::GetNextDataEdit(
     IoStatementState &io, int maxRepeat) {
@@ -818,6 +836,17 @@ ListDirectedStatementState<Direction::Input>::GetNextDataEdit(
   return edit;
 }
 
+template <Direction DIR>
+int ExternalListIoStatementState<DIR>::EndIoStatement() {
+  if constexpr (DIR == Direction::Input) {
+    if (auto status{ListDirectedStatementState<DIR>::EndIoStatement()};
+        status != IostatOk) {
+      return status;
+    }
+  }
+  return ExternalIoStatementState<DIR>::EndIoStatement();
+}
+
 template <Direction DIR>
 bool ExternalUnformattedIoStatementState<DIR>::Receive(
     char *data, std::size_t bytes, std::size_t elementBytes) {
@@ -910,6 +939,16 @@ bool ChildUnformattedIoStatementState<DIR>::Receive(
   return this->child().parent().Receive(data, bytes, elementBytes);
 }
 
+template <Direction DIR> int ChildListIoStatementState<DIR>::EndIoStatement() {
+  if constexpr (DIR == Direction::Input) {
+    if (int status{ListDirectedStatementState<DIR>::EndIoStatement()};
+        status != IostatOk) {
+      return status;
+    }
+  }
+  return ChildIoStatementState<DIR>::EndIoStatement();
+}
+
 template class InternalIoStatementState<Direction::Output>;
 template class InternalIoStatementState<Direction::Input>;
 template class InternalFormattedIoStatementState<Direction::Output>;
diff --git a/flang/runtime/io-stmt.h b/flang/runtime/io-stmt.h
index 91169f6c6e323e..0b6bcbd9af025a 100644
--- a/flang/runtime/io-stmt.h
+++ b/flang/runtime/io-stmt.h
@@ -304,6 +304,7 @@ class ListDirectedStatementState<Direction::Input>
     : public FormattedIoStatementState<Direction::Input> {
 public:
   bool inNamelistSequence() const { return inNamelistSequence_; }
+  int EndIoStatement();
 
   // Skips value separators, handles repetition and null values.
   // Vacant when '/' appears; present with descriptor == ListDirectedNullValue
@@ -317,6 +318,9 @@ class ListDirectedStatementState<Direction::Input>
   // NAMELIST input item.
   void ResetForNextNamelistItem(bool inNamelistSequence) {
     remaining_ = 0;
+    if (repeatPosition_) {
+      repeatPosition_->Cancel();
+    }
     eatComma_ = false;
     realPart_ = imaginaryPart_ = false;
     inNamelistSequence_ = inNamelistSequence;
@@ -399,6 +403,7 @@ class InternalListIoStatementState : public InternalIoStatementState<DIR>,
       const Descriptor &, const char *sourceFile = nullptr, int sourceLine = 0);
   IoStatementState &ioStatementState() { return ioStatementState_; }
   using ListDirectedStatementState<DIR>::GetNextDataEdit;
+  int EndIoStatement();
 
 private:
   IoStatementState ioStatementState_; // points to *this
@@ -474,6 +479,7 @@ class ExternalListIoStatementState : public ExternalIoStatementState<DIR>,
 public:
   using ExternalIoStatementState<DIR>::ExternalIoStatementState;
   using ListDirectedStatementState<DIR>::GetNextDataEdit;
+  int EndIoStatement();
 };
 
 template <Direction DIR>
@@ -532,6 +538,7 @@ class ChildListIoStatementState : public ChildIoStatementState<DIR>,
 public:
   using ChildIoStatementState<DIR>::ChildIoStatementState;
   using ListDirectedStatementState<DIR>::GetNextDataEdit;
+  int EndIoStatement();
 };
 
 template <Direction DIR>