[flang-commits] [flang] [flang] Accept L0 (PR #121998)

[Peter Klausler via flang-commits]

https://github.com/klausler created https://github.com/llvm/llvm-project/pull/121998

Accept a zero field width for formatted logical output (L0), interpreting it as if it had been L1.

>From 7e6eaefb057da72ad96c2157616bb82d6e80bfbf Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Tue, 7 Jan 2025 13:33:04 -0800
Subject: [PATCH] [flang] Accept L0

Accept a zero field width for formatted logical output (L0), interpreting
it as if it had been L1.
---
 flang/docs/Extensions.md                      |  1 +
 flang/include/flang/Common/format.h           | 11 +++++++----
 flang/test/Semantics/io07.f90                 |  4 ++--
 flang/test/Semantics/io08.f90                 |  3 +--
 flang/unittests/Runtime/LogicalFormatTest.cpp |  2 +-
 5 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/flang/docs/Extensions.md b/flang/docs/Extensions.md
index 2d1c967a6068de..6a3186968a58c7 100644
--- a/flang/docs/Extensions.md
+++ b/flang/docs/Extensions.md
@@ -406,6 +406,7 @@ end
 * A character length specifier in a component or entity declaration
   is accepted before an array specification (`ch*3(2)`) as well
   as afterwards.
+* A zero field width is allowed for logical formatted output (`L0`).
 
 ### Extensions supported when enabled by options
 
diff --git a/flang/include/flang/Common/format.h b/flang/include/flang/Common/format.h
index de6967139c5caf..c5e9fb06e260f1 100644
--- a/flang/include/flang/Common/format.h
+++ b/flang/include/flang/Common/format.h
@@ -463,10 +463,13 @@ template <typename CHAR> void FormatValidator<CHAR>::check_r(bool allowed) {
 template <typename CHAR> bool FormatValidator<CHAR>::check_w() {
   if (token_.kind() == TokenKind::UnsignedInteger) {
     wValue_ = integerValue_;
-    if (wValue_ == 0 &&
-        (*argString_ == 'A' || *argString_ == 'L' ||
-            stmt_ == IoStmtKind::Read)) { // C1306, 13.7.2.1p6
-      ReportError("'%s' edit descriptor 'w' value must be positive");
+    if (wValue_ == 0) {
+      if (*argString_ == 'A' || stmt_ == IoStmtKind::Read) {
+        // C1306, 13.7.2.1p6
+        ReportError("'%s' edit descriptor 'w' value must be positive");
+      } else if (*argString_ == 'L') {
+        ReportWarning("'%s' edit descriptor 'w' value should be positive");
+      }
     }
     NextToken();
     return true;
diff --git a/flang/test/Semantics/io07.f90 b/flang/test/Semantics/io07.f90
index 64a32c9959287c..a013849472f611 100644
--- a/flang/test/Semantics/io07.f90
+++ b/flang/test/Semantics/io07.f90
@@ -68,10 +68,10 @@
 6001 format(((I0, B0)))
 
      !ERROR: 'A' edit descriptor 'w' value must be positive
-     !ERROR: 'L' edit descriptor 'w' value must be positive
+     !WARNING: 'L' edit descriptor 'w' value should be positive
 6101 format((A0), ((L0)))
 
-     !ERROR: 'L' edit descriptor 'w' value must be positive
+     !WARNING: 'L' edit descriptor 'w' value should be positive
 6102 format((3(((L 0 0 0)))))
 
 7001 format(17G8.1, 17G8.1e3)
diff --git a/flang/test/Semantics/io08.f90 b/flang/test/Semantics/io08.f90
index f6038b471759f3..517984fe3433d6 100644
--- a/flang/test/Semantics/io08.f90
+++ b/flang/test/Semantics/io08.f90
@@ -192,8 +192,7 @@
   !ERROR: 'A' edit descriptor 'w' value must be positive
   write(*,'(A0)')
 
-  !ERROR: 'L' edit descriptor 'w' value must be positive
-  write(*,'(L0)')
+  write(*,'(L0)') ! warning, not error
 
   !ERROR: Expected 'G' edit descriptor '.d' value
   write(*,'(G4)')
diff --git a/flang/unittests/Runtime/LogicalFormatTest.cpp b/flang/unittests/Runtime/LogicalFormatTest.cpp
index c4fbfc81f06a43..26c9374be13389 100644
--- a/flang/unittests/Runtime/LogicalFormatTest.cpp
+++ b/flang/unittests/Runtime/LogicalFormatTest.cpp
@@ -23,7 +23,7 @@ TEST(IOApiTests, LogicalFormatTest) {
   char buffer[bufferSize];
 
   // Create format for all types and values to be written
-  const char *format{"(L,L3,I3,L2,L2,I3,L2,A3,L2,L,F4.1,L2)"};
+  const char *format{"(L0,L3,I3,L2,L2,I3,L2,A3,L2,L,F4.1,L2)"};
   auto cookie{IONAME(BeginInternalFormattedOutput)(
       buffer, bufferSize, format, std::strlen(format))};