--- old/src/hotspot/share/classfile/javaClasses.cpp	2018-04-10 16:58:48.425013000 +0200
+++ new/src/hotspot/share/classfile/javaClasses.cpp	2018-04-10 16:58:47.976981000 +0200
@@ -4126,7 +4126,7 @@
     ss.print("\"%s\" (instance of %s", name, loader->klass()->external_name());
     seperator = ", ";
   } else {
-    ss.print("%s", loader->klass()->external_name());
+    ss.print("instance of %s", loader->klass()->external_name());
     seperator = " (";
   }
 
--- old/src/hotspot/share/classfile/systemDictionary.cpp	2018-04-10 16:58:49.768142000 +0200
+++ new/src/hotspot/share/classfile/systemDictionary.cpp	2018-04-10 16:58:49.321073000 +0200
@@ -2170,7 +2170,6 @@
       if ((defining == true) || (k != check)) {
         linkage_error1 = "loader ";
         linkage_error2 = " attempted duplicate class definition for ";
-        guarantee(check->class_loader() == class_loader(), "Per construction. Else report the other loader.");
       } else {
         return;
       }
@@ -3107,18 +3106,10 @@
   NOT_PRODUCT(SystemDictionary::verify());
 }
 
-// Return string to give helpful intformation about a classloader.
 // Caller needs ResourceMark.
 const char* SystemDictionary::loader_name(const oop loader) {
-#if INCLUDE_CDS
-  if (DumpSharedSpaces) {
-    // Describe_external() calls assert(is_instance...) in various places,
-    // which may fail with DumpSharedSpaces.
-    if ((loader) == NULL) return "<bootloader>";
-    return InstanceKlass::cast((loader)->klass())->name()->as_C_string();
-  }
-#endif
-  return java_lang_ClassLoader::describe_external(loader);
+  return ((loader) == NULL ? "<bootloader>" :
+          InstanceKlass::cast((loader)->klass())->name()->as_C_string());
 }
 
 // caller needs ResourceMark
--- old/src/hotspot/share/oops/klassVtable.cpp	2018-04-10 16:58:51.497259000 +0200
+++ new/src/hotspot/share/oops/klassVtable.cpp	2018-04-10 16:58:51.040231000 +0200
@@ -24,6 +24,7 @@
 
 #include "precompiled.hpp"
 #include "jvm.h"
+#include "classfile/javaClasses.hpp"
 #include "classfile/systemDictionary.hpp"
 #include "classfile/vmSymbols.hpp"
 #include "interpreter/linkResolver.hpp"
@@ -509,17 +510,17 @@
                 "selected method's type %s, and the class loader %s for its super "
                 "type %s have different Class objects for the type %s used in the signature";
               const char* curr_class = klass->external_name();
-              const char* sig = target_method()->name_and_sig_as_C_string();
+              const char* method = target_method()->name_and_sig_as_C_string();
               const char* loader1 = java_lang_ClassLoader::describe_external(target_loader());
               const char* sel_class = target_klass->external_name();
               const char* loader2 = java_lang_ClassLoader::describe_external(super_loader());
               const char* super_class = super_klass->external_name();
-              char* failed_type_name = failed_type_symbol->as_C_string();
-              size_t buflen = strlen(msg) + strlen(curr_class) + strlen(sig) +
+              const char* failed_type_name = failed_type_symbol->as_klass_external_name();
+              size_t buflen = strlen(msg) + strlen(curr_class) + strlen(method) +
                 strlen(loader1) + strlen(sel_class) + strlen(loader2) +
                 strlen(super_class) + strlen(failed_type_name);
               char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
-              jio_snprintf(buf, buflen, msg, curr_class, sig, loader1, sel_class, loader2,
+              jio_snprintf(buf, buflen, msg, curr_class, method, loader1, sel_class, loader2,
                            super_class, failed_type_name);
               THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
             }
@@ -1245,7 +1246,7 @@
             const char* iface = InstanceKlass::cast(interf)->external_name();
             const char* loader2 = java_lang_ClassLoader::describe_external(method_holder_loader());
             const char* mclass = target()->method_holder()->external_name();
-            const char* failed_type_name = failed_type_symbol->as_C_string();
+            const char* failed_type_name = failed_type_symbol->as_klass_external_name();
             size_t buflen = strlen(msg) + strlen(current) + strlen(sig) +
               strlen(loader1) + strlen(iface) + strlen(loader2) + strlen(mclass) +
               strlen(failed_type_name);