[flang][runtime] Emit leading spaces in NAMELIST output

[klausler]

As NAMELIST output is a variant of list-directed output, its editing must produce leading spaces on (most) output records to effect carriage control. These spaces are required by the language standard and implemented by nearly all other Fortran compilers (except GNU).

Fixes #76798.

[llvmbot]

@llvm/pr-subscribers-flang-runtime

Author: Peter Klausler (klausler)

Changes

As NAMELIST output is a variant of list-directed output, its editing must produce leading spaces on (most) output records to effect carriage control. These spaces are required by the language standard and implemented by nearly all other Fortran compilers (except GNU).

Fixes #76798.

---

Full diff: https://github.com/llvm/llvm-project/pull/76846.diff

2 Files Affected:

• (modified) flang/runtime/namelist.cpp (+15-14)
• (modified) flang/unittests/Runtime/Namelist.cpp (+6-6)

diff --git a/flang/runtime/namelist.cpp b/flang/runtime/namelist.cpp
index e6997bcf945b80..848ebcf300a3d9 100644
--- a/flang/runtime/namelist.cpp
+++ b/flang/runtime/namelist.cpp
@@ -30,16 +30,15 @@ bool IONAME(OutputNamelist)(Cookie cookie, const NamelistGroup &group) {
   IoStatementState &io{*cookie};
   io.CheckFormattedStmtType<Direction::Output>("OutputNamelist");
   io.mutableModes().inNamelist = true;
-  char comma{static_cast<char>(GetComma(io))};
   ConnectionState &connection{io.GetConnectionState()};
-  // Internal functions to advance records and convert case
-  const auto EmitWithAdvance{[&](char ch) -> bool {
-    return (!connection.NeedAdvance(1) || io.AdvanceRecord()) &&
-        EmitAscii(io, &ch, 1);
-  }};
-  const auto EmitUpperCase{[&](const char *str) -> bool {
-    if (connection.NeedAdvance(std::strlen(str)) &&
-        !(io.AdvanceRecord() && EmitAscii(io, " ", 1))) {
+  // Internal function to advance records and convert case
+  const auto EmitUpperCase{[&](const char *prefix, std::size_t prefixLen,
+                               const char *str, char suffix) -> bool {
+    if ((connection.NeedAdvance(prefixLen) &&
+            !(io.AdvanceRecord() && EmitAscii(io, " ", 1))) ||
+        !EmitAscii(io, prefix, prefixLen) ||
+        (connection.NeedAdvance(std::strlen(str) + (suffix != ' ')) &&
+            !(io.AdvanceRecord() && EmitAscii(io, " ", 1)))) {
       return false;
     }
     for (; *str; ++str) {
@@ -49,23 +48,25 @@ bool IONAME(OutputNamelist)(Cookie cookie, const NamelistGroup &group) {
         return false;
       }
     }
-    return true;
+    return suffix == ' ' || EmitAscii(io, &suffix, 1);
   }};
   // &GROUP
-  if (!(EmitWithAdvance('&') && EmitUpperCase(group.groupName))) {
+  if (!EmitUpperCase(" &", 2, group.groupName, ' ')) {
     return false;
   }
   auto *listOutput{io.get_if<ListDirectedStatementState<Direction::Output>>()};
+  char comma{static_cast<char>(GetComma(io))};
+  char prefix{' '};
   for (std::size_t j{0}; j < group.items; ++j) {
     // [,]ITEM=...
     const NamelistGroup::Item &item{group.item[j]};
     if (listOutput) {
       listOutput->set_lastWasUndelimitedCharacter(false);
     }
-    if (!EmitWithAdvance(j == 0 ? ' ' : comma) || !EmitUpperCase(item.name) ||
-        !EmitWithAdvance('=')) {
+    if (!EmitUpperCase(&prefix, 1, item.name, '=')) {
       return false;
     }
+    prefix = comma;
     if (const auto *addendum{item.descriptor.Addendum()};
         addendum && addendum->derivedType()) {
       const NonTbpDefinedIoTable *table{group.nonTbpDefinedIo};
@@ -77,7 +78,7 @@ bool IONAME(OutputNamelist)(Cookie cookie, const NamelistGroup &group) {
     }
   }
   // terminal /
-  return EmitWithAdvance('/');
+  return EmitUpperCase("/", 1, "", ' ');
 }
 
 static constexpr bool IsLegalIdStart(char32_t ch) {
diff --git a/flang/unittests/Runtime/Namelist.cpp b/flang/unittests/Runtime/Namelist.cpp
index 5911d67f0d5fc4..f95c5d2e553aa7 100644
--- a/flang/unittests/Runtime/Namelist.cpp
+++ b/flang/unittests/Runtime/Namelist.cpp
@@ -88,7 +88,7 @@ TEST(NamelistTests, BasicSanity) {
   ASSERT_EQ(outStatus1, 0) << "Failed namelist output sanity, status "
                            << static_cast<int>(outStatus1);
 
-  static const std::string expect{"&GROUP1 INTS= 1 -2 4 -8 16 -32  "
+  static const std::string expect{" &GROUP1 INTS= 1 -2 4 -8 16 -32 "
                                   " 64 -128 256 -512 1024 -2048    "
                                   " 4096 -8192 16384 -32768 65536  "
                                   " -131072 262144 -524288,REALS=  "
@@ -157,7 +157,7 @@ TEST(NamelistTests, Subscripts) {
       << "Failed namelist output subscripts rewrite, status "
       << static_cast<int>(outStatus);
   std::string got{out, sizeof out};
-  static const std::string expect{"&JUSTA A= 0 2 0 0 0 1/                  "};
+  static const std::string expect{" &JUSTA A= 0 2 0 0 0 1/                 "};
   EXPECT_EQ(got, expect);
 }
 
@@ -213,7 +213,7 @@ TEST(NamelistTests, ScalarSubstring) {
   ASSERT_TRUE(IONAME(OutputNamelist)(outCookie, group));
   ASSERT_EQ(IONAME(EndIoStatement)(outCookie), IostatOk) << "namelist output";
   std::string got{out, sizeof out};
-  static const std::string expect{"&JUSTA A= 'aBCDEfgh'/           "};
+  static const std::string expect{" &JUSTA A= 'aBCDEfgh'/          "};
   EXPECT_EQ(got, expect);
 }
 
@@ -242,7 +242,7 @@ TEST(NamelistTests, ArraySubstring) {
   ASSERT_TRUE(IONAME(OutputNamelist)(outCookie, group));
   ASSERT_EQ(IONAME(EndIoStatement)(outCookie), IostatOk) << "namelist output";
   std::string got{out, sizeof out};
-  static const std::string expect{"&JUSTA A= 'aBCDEfgh' 'iJKLMnop'/        "};
+  static const std::string expect{" &JUSTA A= 'aBCDEfgh' 'iJKLMnop'/       "};
   EXPECT_EQ(got, expect);
 }
 
@@ -270,7 +270,7 @@ TEST(NamelistTests, Skip) {
   ASSERT_TRUE(IONAME(OutputNamelist)(outCookie, group));
   ASSERT_EQ(IONAME(EndIoStatement)(outCookie), IostatOk) << "namelist output";
   std::string got{out, sizeof out};
-  static const std::string expect{"&NML J= 123/        "};
+  static const std::string expect{" &NML J= 123/       "};
   EXPECT_EQ(got, expect);
 }
 
@@ -301,7 +301,7 @@ TEST(NamelistTests, Comma) {
   ASSERT_TRUE(IONAME(OutputNamelist)(outCookie, group));
   ASSERT_EQ(IONAME(EndIoStatement)(outCookie), IostatOk) << "namelist output";
   std::string got{out, sizeof out};
-  static const std::string expect{"&NML Z= (-1,;2,) (-3,;,5)/    "};
+  static const std::string expect{" &NML Z= (-1,;2,) (-3,;,5)/   "};
   EXPECT_EQ(got, expect);
 }
 

[psteinfeld]

All builds and tests correctly and looks good.