[flang] Warn for the limit on name length

[peixin]

Summary

As fortran 2018 C601, the maximum length of a name is 63 characters.

[klausler]

flang/lib/Semantics/check-declarations.cpp

204

This message should be a portability warning, not a fatal error.

[peixin]

Change errors into warnings.

[klausler]

flang/lib/Semantics/check-declarations.cpp

204

Portability warnings are "xxxx"_port_en_US.

[peixin]

Change into the portability warning.

[peixin]

flang/lib/Semantics/check-declarations.cpp

204

Thanks. Fixed. I don't find the test cases for this kind of warnings, so I remove the test case.

flang/include/flang/Common/Fortran.h

enum class RoundingMode : std::uint8_t {
   TiesAwayFromZero, // ROUND=COMPATIBLE, RC - ties round away from zero
 };
 
 // Fortran label. Must be in [1..99999].
 using Label = std::uint64_t;
 
 // Fortran arrays may have up to 15 dimensions (See Fortran 2018 section 5.4.6).
 static constexpr int maxRank{15};
+
+// Fortran names may have up to 63 characters (See Fortran 2018 C601).
+static constexpr int maxNameLen{63};
 } // namespace Fortran::common
 #endif // FORTRAN_COMMON_FORTRAN_H_

flang/lib/Semantics/check-declarations.cpp

void CheckHelper::Check(
   } else if (const DerivedTypeSpec * derived{type.AsDerived()}) {
     for (auto &parm : derived->parameters()) {
       Check(parm.second, canHaveAssumedTypeParameters);
     }
   }
 }
 
 void CheckHelper::Check(const Symbol &symbol) {
+  if (symbol.name().size() > common::maxNameLen) {
+    messages_.Say(symbol.name(),
+        "%s has length %d, which is greater than the maximum name length "
+        "%d"_port_en_US,
+        symbol.name(), symbol.name().size(), common::maxNameLen);
+  }
   if (context_.HasError(symbol)) {
     return;
   }
   auto restorer{messages_.SetLocation(symbol.name())};
   context_.set_location(symbol.name());
   const DeclTypeSpec *type{symbol.GetType()};
   const DerivedTypeSpec *derived{type ? type->AsDerived() : nullptr};
   bool isDone{false};