8067662: "java.lang.NullPointerException: Method name is null" from StackTraceElement.<init>

Summary: use method cpref and klass version to provide meaningful methods name in stacktraces
Reviewed-by: coleenp, dcubed

src/share/vm/classfile/javaClasses.cpp

 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1278,7 +1278,8 @@ static inline int version_at(unsigned int merged) {
 }
 
 static inline bool version_matches(Method* method, int version) {
-  return (method->constants()->version() == version && version < MAX_VERSION);
+  assert(version < MAX_VERSION, "version is too big");
+  return method != NULL && (method->constants()->version() == version);
 }
 
 static inline int get_line_number(Method* method, int bci) {
@@ -1308,6 +1309,7 @@ class BacktraceBuilder: public StackObj {
   typeArrayOop    _methods;
   typeArrayOop    _bcis;
   objArrayOop     _mirrors;
+  typeArrayOop    _cprefs; // needed to insulate method name against redefinition
   int             _index;
   No_Safepoint_Verifier _nsv;
 
@@ -1317,6 +1319,7 @@ class BacktraceBuilder: public StackObj {
     trace_methods_offset = java_lang_Throwable::trace_methods_offset,
     trace_bcis_offset    = java_lang_Throwable::trace_bcis_offset,
     trace_mirrors_offset = java_lang_Throwable::trace_mirrors_offset,
+    trace_cprefs_offset  = java_lang_Throwable::trace_cprefs_offset,
     trace_next_offset    = java_lang_Throwable::trace_next_offset,
     trace_size           = java_lang_Throwable::trace_size,
     trace_chunk_size     = java_lang_Throwable::trace_chunk_size
@@ -1338,9 +1341,14 @@ class BacktraceBuilder: public StackObj {
     assert(mirrors != NULL, "mirror array should be initialized in backtrace");
     return mirrors;
   }
+  static typeArrayOop get_cprefs(objArrayHandle chunk) {
+    typeArrayOop cprefs = typeArrayOop(chunk->obj_at(trace_cprefs_offset));
+    assert(cprefs != NULL, "cprefs array should be initialized in backtrace");
+    return cprefs;
+  }
 
   // constructor for new backtrace
-  BacktraceBuilder(TRAPS): _methods(NULL), _bcis(NULL), _head(NULL), _mirrors(NULL) {
+  BacktraceBuilder(TRAPS): _methods(NULL), _bcis(NULL), _head(NULL), _mirrors(NULL), _cprefs(NULL) {
     expand(CHECK);
     _backtrace = _head;
     _index = 0;
@@ -1350,6 +1358,7 @@ class BacktraceBuilder: public StackObj {
     _methods = get_methods(backtrace);
     _bcis = get_bcis(backtrace);
     _mirrors = get_mirrors(backtrace);
+    _cprefs = get_cprefs(backtrace);
     assert(_methods->length() == _bcis->length() &&
            _methods->length() == _mirrors->length(),
            "method and source information arrays should match");
@@ -1375,17 +1384,22 @@ class BacktraceBuilder: public StackObj {
     objArrayOop mirrors = oopFactory::new_objectArray(trace_chunk_size, CHECK);
     objArrayHandle new_mirrors(THREAD, mirrors);
 
+    typeArrayOop cprefs = oopFactory::new_shortArray(trace_chunk_size, CHECK);
+    typeArrayHandle new_cprefs(THREAD, cprefs);
+
     if (!old_head.is_null()) {
       old_head->obj_at_put(trace_next_offset, new_head());
     }
     new_head->obj_at_put(trace_methods_offset, new_methods());
     new_head->obj_at_put(trace_bcis_offset, new_bcis());
     new_head->obj_at_put(trace_mirrors_offset, new_mirrors());
+    new_head->obj_at_put(trace_cprefs_offset, new_cprefs());
 
     _head    = new_head();
     _methods = new_methods();
     _bcis = new_bcis();
     _mirrors = new_mirrors();
+    _cprefs  = new_cprefs();
     _index = 0;
   }
 
@@ -1405,8 +1419,9 @@ class BacktraceBuilder: public StackObj {
       method = mhandle();
     }
 
-    _methods->short_at_put(_index, method->method_idnum());
+    _methods->short_at_put(_index, method->orig_method_idnum());
     _bcis->int_at_put(_index, merge_bci_and_version(bci, method->constants()->version()));
+    _cprefs->short_at_put(_index, method->name_index());
 
     // We need to save the mirrors in the backtrace to keep the class
     // from being unloaded while we still have this stack trace.
@@ -1419,27 +1434,26 @@ class BacktraceBuilder: public StackObj {
 
 // Print stack trace element to resource allocated buffer
 char* java_lang_Throwable::print_stack_element_to_buffer(Handle mirror,
-                                  int method_id, int version, int bci) {
+                                  int method_id, int version, int bci, int cpref) {
 
   // Get strings and string lengths
   InstanceKlass* holder = InstanceKlass::cast(java_lang_Class::as_Klass(mirror()));
   const char* klass_name  = holder->external_name();
   int buf_len = (int)strlen(klass_name);
 
-  // The method id may point to an obsolete method, can't get more stack information
-  Method* method = holder->method_with_idnum(method_id);
-  if (method == NULL) {
-    char* buf = NEW_RESOURCE_ARRAY(char, buf_len + 64);
-    // This is what the java code prints in this case - added Redefined
-    sprintf(buf, "\tat %s.null (Redefined)", klass_name);
-    return buf;
-  }
+  Method* method = holder->method_with_orig_idnum(method_id, version);
 
-  char* method_name = method->name()->as_C_string();
+  // The method can be NULL if the requested class version is gone
+  Symbol* sym = (method != NULL) ? method->name() : holder->constants()->symbol_at(cpref);
+  char* method_name = sym->as_C_string();
   buf_len += (int)strlen(method_name);
 
+  // Use a specific ik version as a holder since the mirror might
+  // refer to a version that is now obsolete and no longer accessible
+  // via the previous versions list.
+  holder = holder->get_klass_version(version);
   char* source_file_name = NULL;
-  if (version_matches(method, version)) {
+  if (holder != NULL) {
     Symbol* source = holder->source_file_name();
     if (source != NULL) {
       source_file_name = source->as_C_string();
@@ -1481,17 +1495,18 @@ char* java_lang_Throwable::print_stack_element_to_buffer(Handle mirror,
 }
 
 void java_lang_Throwable::print_stack_element(outputStream *st, Handle mirror,
-                                              int method_id, int version, int bci) {
+                                              int method_id, int version, int bci, int cpref) {
   ResourceMark rm;
-  char* buf = print_stack_element_to_buffer(mirror, method_id, version, bci);
+  char* buf = print_stack_element_to_buffer(mirror, method_id, version, bci, cpref);
   st->print_cr("%s", buf);
 }
 
 void java_lang_Throwable::print_stack_element(outputStream *st, methodHandle method, int bci) {
   Handle mirror = method->method_holder()->java_mirror();
-  int method_id = method->method_idnum();
+  int method_id = method->orig_method_idnum();
   int version = method->constants()->version();
-  print_stack_element(st, mirror, method_id, version, bci);
+  int cpref = method->name_index();
+  print_stack_element(st, mirror, method_id, version, bci, cpref);
 }
 
 const char* java_lang_Throwable::no_stack_trace_message() {
@@ -1516,6 +1531,7 @@ void java_lang_Throwable::print_stack_trace(oop throwable, outputStream* st) {
       typeArrayHandle methods (THREAD, BacktraceBuilder::get_methods(result));
       typeArrayHandle bcis (THREAD, BacktraceBuilder::get_bcis(result));
       objArrayHandle mirrors (THREAD, BacktraceBuilder::get_mirrors(result));
+      typeArrayHandle cprefs (THREAD, BacktraceBuilder::get_cprefs(result));
 
       int length = methods()->length();
       for (int index = 0; index < length; index++) {
@@ -1525,7 +1541,8 @@ void java_lang_Throwable::print_stack_trace(oop throwable, outputStream* st) {
         int method = methods->short_at(index);
         int version = version_at(bcis->int_at(index));
         int bci = bci_at(bcis->int_at(index));
-        print_stack_element(st, mirror, method, version, bci);
+        int cpref = cprefs->short_at(index);
+        print_stack_element(st, mirror, method, version, bci, cpref);
       }
       result = objArrayHandle(THREAD, objArrayOop(result->obj_at(trace_next_offset)));
     }
@@ -1809,29 +1826,30 @@ oop java_lang_Throwable::get_stack_trace_element(oop throwable, int index, TRAPS
   if (chunk == NULL) {
     THROW_(vmSymbols::java_lang_IndexOutOfBoundsException(), NULL);
   }
-  // Get method id, bci, version and mirror from chunk
+  // Get method id, bci, version, mirror and cpref from chunk
   typeArrayOop methods = BacktraceBuilder::get_methods(chunk);
   typeArrayOop bcis = BacktraceBuilder::get_bcis(chunk);
   objArrayOop mirrors = BacktraceBuilder::get_mirrors(chunk);
+  typeArrayOop cprefs = BacktraceBuilder::get_cprefs(chunk);
 
   assert(methods != NULL && bcis != NULL && mirrors != NULL, "sanity check");
 
   int method = methods->short_at(chunk_index);
   int version = version_at(bcis->int_at(chunk_index));
   int bci = bci_at(bcis->int_at(chunk_index));
+  int cpref = cprefs->short_at(chunk_index);
   Handle mirror(THREAD, mirrors->obj_at(chunk_index));
 
   // Chunk can be partial full
   if (mirror.is_null()) {
     THROW_(vmSymbols::java_lang_IndexOutOfBoundsException(), NULL);
   }
-
-  oop element = java_lang_StackTraceElement::create(mirror, method, version, bci, CHECK_0);
+  oop element = java_lang_StackTraceElement::create(mirror, method, version, bci, cpref, CHECK_0);
   return element;
 }
 
 oop java_lang_StackTraceElement::create(Handle mirror, int method_id,
-                                        int version, int bci, TRAPS) {
+                                        int version, int bci, int cpref, TRAPS) {
   // Allocate java.lang.StackTraceElement instance
   Klass* k = SystemDictionary::StackTraceElement_klass();
   assert(k != NULL, "must be loaded in 1.4+");
@@ -1848,17 +1866,13 @@ oop java_lang_StackTraceElement::create(Handle mirror, int method_id,
   oop classname = StringTable::intern((char*) str, CHECK_0);
   java_lang_StackTraceElement::set_declaringClass(element(), classname);
 
-  Method* method = holder->method_with_idnum(method_id);
-  // Method on stack may be obsolete because it was redefined so cannot be
-  // found by idnum.
-  if (method == NULL) {
-    // leave name and fileName null
-    java_lang_StackTraceElement::set_lineNumber(element(), -1);
-    return element();
-  }
+  Method* method = holder->method_with_orig_idnum(method_id, version);
+
+  // The method can be NULL if the requested class version is gone
+  Symbol* sym = (method != NULL) ? method->name() : holder->constants()->symbol_at(cpref);
 
   // Fill in method name
-  oop methodname = StringTable::intern(method->name(), CHECK_0);
+  oop methodname = StringTable::intern(sym, CHECK_0);
   java_lang_StackTraceElement::set_methodName(element(), methodname);
 
   if (!version_matches(method, version)) {
@@ -1867,6 +1881,11 @@ oop java_lang_StackTraceElement::create(Handle mirror, int method_id,
     java_lang_StackTraceElement::set_lineNumber(element(), -1);
   } else {
     // Fill in source file name and line number.
+    // Use a specific ik version as a holder since the mirror might
+    // refer to a version that is now obsolete and no longer accessible
+    // via the previous versions list.
+    holder = holder->get_klass_version(version);
+    assert(holder != NULL, "sanity check");
     Symbol* source = holder->source_file_name();
     if (ShowHiddenFrames && source == NULL)
       source = vmSymbols::unknown_class_name();
@@ -1881,8 +1900,9 @@ oop java_lang_StackTraceElement::create(Handle mirror, int method_id,
 
 oop java_lang_StackTraceElement::create(methodHandle method, int bci, TRAPS) {
   Handle mirror (THREAD, method->method_holder()->java_mirror());
-  int method_id = method->method_idnum();
-  return create(mirror, method_id, method->constants()->version(), bci, THREAD);
+  int method_id = method->orig_method_idnum();
+  int cpref = method->name_index();
+  return create(mirror, method_id, method->constants()->version(), bci, cpref, THREAD);
 }
 
 void java_lang_reflect_AccessibleObject::compute_offsets() {

src/share/vm/classfile/javaClasses.hpp

 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -484,8 +484,9 @@ class java_lang_Throwable: AllStatic {
     trace_methods_offset = 0,
     trace_bcis_offset    = 1,
     trace_mirrors_offset = 2,
-    trace_next_offset    = 3,
-    trace_size           = 4,
+    trace_cprefs_offset  = 3,
+    trace_next_offset    = 4,
+    trace_size           = 5,
     trace_chunk_size     = 32
   };
 
@@ -496,7 +497,7 @@ class java_lang_Throwable: AllStatic {
   static int static_unassigned_stacktrace_offset;
 
   // Printing
-  static char* print_stack_element_to_buffer(Handle mirror, int method, int version, int bci);
+  static char* print_stack_element_to_buffer(Handle mirror, int method, int version, int bci, int cpref);
   // StackTrace (programmatic access, new since 1.4)
   static void clear_stacktrace(oop throwable);
   // No stack trace available
@@ -517,7 +518,7 @@ class java_lang_Throwable: AllStatic {
   static oop message(Handle throwable);
   static void set_message(oop throwable, oop value);
   static void print_stack_element(outputStream *st, Handle mirror, int method,
-                                  int version, int bci);
+                                  int version, int bci, int cpref);
   static void print_stack_element(outputStream *st, methodHandle method, int bci);
   static void print_stack_usage(Handle stream);
 
@@ -1326,7 +1327,7 @@ class java_lang_StackTraceElement: AllStatic {
   static void set_lineNumber(oop element, int value);
 
   // Create an instance of StackTraceElement
-  static oop create(Handle mirror, int method, int version, int bci, TRAPS);
+  static oop create(Handle mirror, int method, int version, int bci, int cpref, TRAPS);
   static oop create(methodHandle method, int bci, TRAPS);
 
   // Debugging

src/share/vm/oops/instanceKlass.cpp

@@ -3747,6 +3747,22 @@ bool InstanceKlass::has_previous_version() const {
 } // end has_previous_version()
 
 
+InstanceKlass* InstanceKlass::get_klass_version(int version) {
+  if (constants()->version() == version) {
+    return this;
+  }
+  PreviousVersionWalker pvw(Thread::current(), (InstanceKlass*)this);
+  for (PreviousVersionNode * pv_node = pvw.next_previous_version();
+       pv_node != NULL; pv_node = pvw.next_previous_version()) {
+    ConstantPool* prev_cp = pv_node->prev_constant_pool();
+    if (prev_cp->version() == version) {
+      return prev_cp->pool_holder();
+    }
+  }
+  return NULL; // None found
+}
+
+
 Method* InstanceKlass::method_with_idnum(int idnum) {
   Method* m = NULL;
   if (idnum < methods()->length()) {
@@ -3765,6 +3781,37 @@ Method* InstanceKlass::method_with_idnum(int idnum) {
   return m;
 }
 
+
+Method* InstanceKlass::method_with_orig_idnum(int idnum) {
+  if (idnum >= methods()->length()) {
+    return NULL;
+  }
+  Method* m = methods()->at(idnum);
+  if (m != NULL && m->orig_method_idnum() == idnum) {
+    return m;
+  }
+  // Obsolete method idnum does not match the original idnum
+  for (int index = 0; index < methods()->length(); ++index) {
+    m = methods()->at(index);
+    if (m->orig_method_idnum() == idnum) {
+      return m;
+    }
+  }
+  // None found, return null for the caller to handle.
+  return NULL;
+}
+
+
+Method* InstanceKlass::method_with_orig_idnum(int idnum, int version) {
+  InstanceKlass* holder = get_klass_version(version);
+  if (holder == NULL) {
+    return NULL; // The version of klass is gone, no method is found
+  }
+  Method* method = holder->method_with_orig_idnum(idnum);
+  return method;
+}
+
+
 jint InstanceKlass::get_cached_class_file_len() {
   return VM_RedefineClasses::get_cached_class_file_len(_cached_class_file);
 }

src/share/vm/oops/instanceKlass.hpp

@@ -358,6 +358,8 @@ class InstanceKlass: public Klass {
   Array<Method*>* methods() const          { return _methods; }
   void set_methods(Array<Method*>* a)      { _methods = a; }
   Method* method_with_idnum(int idnum);
+  Method* method_with_orig_idnum(int idnum);
+  Method* method_with_orig_idnum(int idnum, int version);
 
   // method ordering
   Array<int>* method_ordering() const     { return _method_ordering; }
@@ -658,6 +660,7 @@ class InstanceKlass: public Klass {
     return _previous_versions;
   }
 
+  InstanceKlass* get_klass_version(int version);
   static void purge_previous_versions(InstanceKlass* ik);
 
   // JVMTI: Support for caching a class file before it is modified by an agent that can do retransformation