[core] Lock calls to TMetaUtils in TClingTypeInfo

Even though it would be better to place the locks in TMetaUtils
directly, TClingUtils.cxx cannot depend from TInterpreter.h (for the
declaration of gInterpreterMutex) as that would cause a circular
dependency. For now, leave the locks in TClingTypeInfo.

core/metacling/src/TClingTypeInfo.cxx

@@ -108,6 +108,8 @@ const char *TClingTypeInfo::Name() const
    TTHREAD_TLS_DECL( std::string, buf);
    buf.clear();
 
+   // TODO: This needs to be locked, but the lock cannot be placed in TClingUtils.cxx as it cannot depend from
+   // TInterpreter.h for the declaration of gInterpreterMutex. Or can it?
    R__LOCKGUARD(gInterpreterMutex);
    ROOT::TMetaUtils::GetFullyQualifiedTypeName(buf,fQualType,*fInterp);
    return buf.c_str();  // NOLINT
@@ -242,6 +244,9 @@ const char *TClingTypeInfo::TrueName(const ROOT::TMetaUtils::TNormalizedCtxt &no
    TTHREAD_TLS_DECL( std::string, buf);
    buf.clear();
 
+   // TODO: This needs to be locked, but the lock cannot be placed in TClingUtils.cxx as it cannot depend from
+   // TInterpreter.h for the declaration of gInterpreterMutex. Or can it?
+   R__LOCKGUARD(gInterpreterMutex);
    ROOT::TMetaUtils::GetNormalizedName(buf,fQualType, *fInterp, normCtxt);
 
    return buf.c_str(); // NOLINT
@@ -257,6 +262,10 @@ std::string TClingTypeInfo::NormalizedName(const ROOT::TMetaUtils::TNormalizedCt
       return "";
    }
    std::string buf;
+
+   // TODO: This needs to be locked, but the lock cannot be placed in TClingUtils.cxx as it cannot depend from
+   // TInterpreter.h for the declaration of gInterpreterMutex. Or can it?
+   R__LOCKGUARD(gInterpreterMutex);
    ROOT::TMetaUtils::GetNormalizedName(buf,fQualType, *fInterp, normCtxt);
 
    // in C++11 this will be efficient thanks to the move constructor.