[flang][runtime] Handle NAN(...) in namelist input (#153101)

The various per-type functions for list-directed (including namelist)
input editing all call a common function to detect whether the next
token of input is the name of a namelist item. This check simply
determines whether this next token looks like an identifier followed by
'=', '(', or '%', and this fails when the next item of input is a NAN
with parenthesized stuff afterwards. Make the check smarter so that it
ensures that any upcoming possible identifier is actually the name of an
item in the namelist group. (And that's tricky too when the group has an
array item named "nan" and the upcoming input is "nan("; see the
newly-added unit test case.)

Fixes https://github.com/llvm/llvm-project/issues/152538.

more

flang-rt/include/flang-rt/runtime/io-stmt.h

@@ -438,7 +438,9 @@ template <>
 class ListDirectedStatementState<Direction::Input>
     : public FormattedIoStatementState<Direction::Input> {
 public:
-  RT_API_ATTRS bool inNamelistSequence() const { return inNamelistSequence_; }
+  RT_API_ATTRS const NamelistGroup *namelistGroup() const {
+    return namelistGroup_;
+  }
   RT_API_ATTRS int EndIoStatement();
 
   // Skips value separators, handles repetition and null values.
@@ -451,18 +453,19 @@ public:
   // input statement.  This member function resets some state so that
   // repetition and null values work correctly for each successive
   // NAMELIST input item.
-  RT_API_ATTRS void ResetForNextNamelistItem(bool inNamelistSequence) {
+  RT_API_ATTRS void ResetForNextNamelistItem(
+      const NamelistGroup *namelistGroup) {
     remaining_ = 0;
     if (repeatPosition_) {
       repeatPosition_->Cancel();
     }
     eatComma_ = false;
     realPart_ = imaginaryPart_ = false;
-    inNamelistSequence_ = inNamelistSequence;
+    namelistGroup_ = namelistGroup;
   }
 
 protected:
-  bool inNamelistSequence_{false};
+  const NamelistGroup *namelistGroup_{nullptr};
 
 private:
   int remaining_{0}; // for "r*" repetition

flang-rt/lib/runtime/edit-input.cpp

@@ -534,7 +534,7 @@ static RT_API_ATTRS ScannedRealInput ScanRealInput(
       next = io.NextInField(remaining, edit);
     }
     if (!next || *next == ')') { // NextInField fails on separators like ')'
-      std::size_t byteCount{0};
+      std::size_t byteCount{1};
       if (!next) {
         next = io.GetCurrentChar(byteCount);
       }

flang-rt/lib/runtime/io-stmt.cpp

@@ -1086,7 +1086,7 @@ ChildListIoStatementState<DIR>::ChildListIoStatementState(
   if constexpr (DIR == Direction::Input) {
     if (auto *listInput{child.parent()
                 .get_if<ListDirectedStatementState<Direction::Input>>()}) {
-      this->inNamelistSequence_ = listInput->inNamelistSequence();
+      this->namelistGroup_ = listInput->namelistGroup();
     }
   }
 #else

flang-rt/lib/runtime/namelist.cpp

@@ -44,8 +44,7 @@ bool IODEF(OutputNamelist)(Cookie cookie, const NamelistGroup &group) {
     if ((connection.NeedAdvance(prefixLen) &&
             !(io.AdvanceRecord() && EmitAscii(io, " ", 1))) ||
         !EmitAscii(io, prefix, prefixLen) ||
-        (connection.NeedAdvance(
+        (connection.NeedAdvance(runtime::strlen(str) + (suffix != ' ')) &&
-             Fortran::runtime::strlen(str) + (suffix != ' ')) &&
             !(io.AdvanceRecord() && EmitAscii(io, " ", 1)))) {
       return false;
     }
@@ -102,8 +101,8 @@ static constexpr RT_API_ATTRS char NormalizeIdChar(char32_t ch) {
   return static_cast<char>(ch >= 'A' && ch <= 'Z' ? ch - 'A' + 'a' : ch);
 }
 
-static RT_API_ATTRS bool GetLowerCaseName(
+static RT_API_ATTRS bool GetLowerCaseName(IoStatementState &io, char buffer[],
-    IoStatementState &io, char buffer[], std::size_t maxLength) {
+    std::size_t maxLength, bool crashIfTooLong = true) {
   std::size_t byteLength{0};
   if (auto ch{io.GetNextNonBlank(byteLength)}) {
     if (IsLegalIdStart(*ch)) {
@@ -117,8 +116,10 @@ static RT_API_ATTRS bool GetLowerCaseName(
       if (j <= maxLength) {
         return true;
       }
-      io.GetIoErrorHandler().SignalError(
+      if (crashIfTooLong) {
-          "Identifier '%s...' in NAMELIST input group is too long", buffer);
+        io.GetIoErrorHandler().SignalError(
+            "Identifier '%s...' in NAMELIST input group is too long", buffer);
+      }
     }
   }
   return false;
@@ -356,9 +357,8 @@ static RT_API_ATTRS bool HandleComponent(IoStatementState &io, Descriptor &desc,
     const DescriptorAddendum *addendum{source.Addendum()};
     if (const typeInfo::DerivedType *
         type{addendum ? addendum->derivedType() : nullptr}) {
-      if (const typeInfo::Component *
+      if (const typeInfo::Component *comp{
-          comp{type->FindDataComponent(
+              type->FindDataComponent(compName, runtime::strlen(compName))}) {
-              compName, Fortran::runtime::strlen(compName))}) {
         bool createdDesc{false};
         if (comp->rank() > 0 && source.rank() > 0) {
           // If base and component are both arrays, the component name
@@ -484,7 +484,7 @@ bool IODEF(InputNamelist)(Cookie cookie, const NamelistGroup &group) {
       handler.SignalError("NAMELIST input group has no name");
       return false;
     }
-    if (Fortran::runtime::strcmp(group.groupName, name) == 0) {
+    if (runtime::strcmp(group.groupName, name) == 0) {
       break; // found it
     }
     SkipNamelistGroup(io);
@@ -503,7 +503,7 @@ bool IODEF(InputNamelist)(Cookie cookie, const NamelistGroup &group) {
     }
     std::size_t itemIndex{0};
     for (; itemIndex < group.items; ++itemIndex) {
-      if (Fortran::runtime::strcmp(name, group.item[itemIndex].name) == 0) {
+      if (runtime::strcmp(name, group.item[itemIndex].name) == 0) {
         break;
       }
     }
@@ -577,13 +577,14 @@ bool IODEF(InputNamelist)(Cookie cookie, const NamelistGroup &group) {
     if (const auto *addendum{useDescriptor->Addendum()};
         addendum && addendum->derivedType()) {
       const NonTbpDefinedIoTable *table{group.nonTbpDefinedIo};
-      listInput->ResetForNextNamelistItem(/*inNamelistSequence=*/true);
+      listInput->ResetForNextNamelistItem(&group);
       if (!IONAME(InputDerivedType)(cookie, *useDescriptor, table) &&
           handler.InError()) {
         return false;
       }
     } else {
-      listInput->ResetForNextNamelistItem(useDescriptor->rank() > 0);
+      listInput->ResetForNextNamelistItem(
+          useDescriptor->rank() > 0 ? &group : nullptr);
       if (!descr::DescriptorIO<Direction::Input>(io, *useDescriptor) &&
           handler.InError()) {
         return false;
@@ -607,27 +608,51 @@ bool IODEF(InputNamelist)(Cookie cookie, const NamelistGroup &group) {
 }
 
 RT_API_ATTRS bool IsNamelistNameOrSlash(IoStatementState &io) {
-  if (auto *listInput{
+  auto *listInput{io.get_if<ListDirectedStatementState<Direction::Input>>()};
-          io.get_if<ListDirectedStatementState<Direction::Input>>()}) {
+  if (!listInput || !listInput->namelistGroup()) {
-    if (listInput->inNamelistSequence()) {
+    return false; // not namelist
-      SavedPosition savedPosition{io};
+  }
-      std::size_t byteCount{0};
+  SavedPosition savedPosition{io};
-      if (auto ch{io.GetNextNonBlank(byteCount)}) {
+  std::size_t byteCount{0};
-        if (IsLegalIdStart(*ch)) {
+  auto ch{io.GetNextNonBlank(byteCount)};
-          do {
+  if (!ch) {
-            io.HandleRelativePosition(byteCount);
+    return false;
-            ch = io.GetCurrentChar(byteCount);
+  } else if (!IsLegalIdStart(*ch)) {
-          } while (ch && IsLegalIdChar(*ch));
+    return *ch == '/' || *ch == '&' || *ch == '$';
-          ch = io.GetNextNonBlank(byteCount);
+  }
-          // TODO: how to deal with NaN(...) ambiguity?
+  char id[nameBufferSize];
-          return ch && (*ch == '=' || *ch == '(' || *ch == '%');
+  if (!GetLowerCaseName(io, id, sizeof id, /*crashIfTooLong=*/false)) {
-        } else {
+    return true; // long name
-          return *ch == '/' || *ch == '&' || *ch == '$';
+  }
-        }
+  // It looks like a name, but might be "inf" or "nan".  Check what
-      }
+  // follows.
+  ch = io.GetNextNonBlank(byteCount);
+  if (!ch) {
+    return false;
+  } else if (*ch == '=' || *ch == '%') {
+    return true;
+  } else if (*ch != '(') {
+    return false;
+  } else if (runtime::strcmp(id, "nan") != 0) {
+    return true;
+  }
+  // "nan(" ambiguity
+  int depth{1};
+  while (true) {
+    io.HandleRelativePosition(byteCount);
+    ch = io.GetNextNonBlank(byteCount);
+    if (depth == 0) {
+      // nan(...) followed by '=', '%', or '('?
+      break;
+    } else if (!ch) {
+      return true; // not a valid NaN(...)
+    } else if (*ch == '(') {
+      ++depth;
+    } else if (*ch == ')') {
+      --depth;
     }
   }
-  return false;
+  return ch && (*ch == '=' || *ch == '%' || *ch == '(');
 }
 
 RT_OFFLOAD_API_GROUP_END

flang-rt/unittests/Runtime/Namelist.cpp

@@ -334,4 +334,35 @@ TEST(NamelistTests, RealValueForInt) {
   EXPECT_EQ(got, expect);
 }
 
+TEST(NamelistTests, NanInputAmbiguity) {
+  OwningPtr<Descriptor> xDesc{// real :: x(5) = 0.
+      MakeArray<TypeCategory::Real, static_cast<int>(sizeof(float))>(
+          std::vector<int>{5}, std::vector<float>{{0, 0, 0, 0, 0}})};
+  OwningPtr<Descriptor> nanDesc{// real :: nan(2) = 0.
+      MakeArray<TypeCategory::Real, static_cast<int>(sizeof(float))>(
+          std::vector<int>{2}, std::vector<float>{{0, 0}})};
+  const NamelistGroup::Item items[]{{"x", *xDesc}, {"nan", *nanDesc}};
+  const NamelistGroup group{"nml", 2, items};
+  static char t1[]{"&nml x=1 2 nan(q) 4 nan(1)=5 nan(q)/"};
+  StaticDescriptor<1, true> statDesc;
+  Descriptor &internalDesc{statDesc.descriptor()};
+  internalDesc.Establish(TypeCode{CFI_type_char},
+      /*elementBytes=*/std::strlen(t1), t1, 0, nullptr, CFI_attribute_pointer);
+  auto inCookie{IONAME(BeginInternalArrayListInput)(
+      internalDesc, nullptr, 0, __FILE__, __LINE__)};
+  ASSERT_TRUE(IONAME(InputNamelist)(inCookie, group));
+  ASSERT_EQ(IONAME(EndIoStatement)(inCookie), IostatOk)
+      << "namelist real input for nans";
+  char out[40];
+  internalDesc.Establish(TypeCode{CFI_type_char}, /*elementBytes=*/sizeof out,
+      out, 0, nullptr, CFI_attribute_pointer);
+  auto outCookie{IONAME(BeginInternalArrayListOutput)(
+      internalDesc, nullptr, 0, __FILE__, __LINE__)};
+  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 X= 1. 2. NaN 4. 0.,NAN= 5. NaN/   "};
+  EXPECT_EQ(got, expect);
+}
+
 // TODO: Internal NAMELIST error tests