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The klass.cpp Java example source code
/*
* Copyright (c) 1997, 2013, 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
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/dictionary.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "gc_implementation/shared/markSweep.inline.hpp"
#include "gc_interface/collectedHeap.inline.hpp"
#include "memory/heapInspection.hpp"
#include "memory/metadataFactory.hpp"
#include "memory/oopFactory.hpp"
#include "memory/resourceArea.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klass.inline.hpp"
#include "oops/oop.inline2.hpp"
#include "runtime/atomic.hpp"
#include "trace/traceMacros.hpp"
#include "utilities/stack.hpp"
#include "utilities/macros.hpp"
#if INCLUDE_ALL_GCS
#include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
#include "gc_implementation/parallelScavenge/psPromotionManager.hpp"
#include "gc_implementation/parallelScavenge/psScavenge.hpp"
#endif // INCLUDE_ALL_GCS
void Klass::set_name(Symbol* n) {
_name = n;
if (_name != NULL) _name->increment_refcount();
}
bool Klass::is_subclass_of(const Klass* k) const {
// Run up the super chain and check
if (this == k) return true;
Klass* t = const_cast<Klass*>(this)->super();
while (t != NULL) {
if (t == k) return true;
t = t->super();
}
return false;
}
bool Klass::search_secondary_supers(Klass* k) const {
// Put some extra logic here out-of-line, before the search proper.
// This cuts down the size of the inline method.
// This is necessary, since I am never in my own secondary_super list.
if (this == k)
return true;
// Scan the array-of-objects for a match
int cnt = secondary_supers()->length();
for (int i = 0; i < cnt; i++) {
if (secondary_supers()->at(i) == k) {
((Klass*)this)->set_secondary_super_cache(k);
return true;
}
}
return false;
}
// Return self, except for abstract classes with exactly 1
// implementor. Then return the 1 concrete implementation.
Klass *Klass::up_cast_abstract() {
Klass *r = this;
while( r->is_abstract() ) { // Receiver is abstract?
Klass *s = r->subklass(); // Check for exactly 1 subklass
if( !s || s->next_sibling() ) // Oops; wrong count; give up
return this; // Return 'this' as a no-progress flag
r = s; // Loop till find concrete class
}
return r; // Return the 1 concrete class
}
// Find LCA in class hierarchy
Klass *Klass::LCA( Klass *k2 ) {
Klass *k1 = this;
while( 1 ) {
if( k1->is_subtype_of(k2) ) return k2;
if( k2->is_subtype_of(k1) ) return k1;
k1 = k1->super();
k2 = k2->super();
}
}
void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
ResourceMark rm(THREAD);
THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
: vmSymbols::java_lang_InstantiationException(), external_name());
}
void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
THROW(vmSymbols::java_lang_ArrayStoreException());
}
void Klass::initialize(TRAPS) {
ShouldNotReachHere();
}
bool Klass::compute_is_subtype_of(Klass* k) {
assert(k->is_klass(), "argument must be a class");
return is_subclass_of(k);
}
Method* Klass::uncached_lookup_method(Symbol* name, Symbol* signature) const {
#ifdef ASSERT
tty->print_cr("Error: uncached_lookup_method called on a klass oop."
" Likely error: reflection method does not correctly"
" wrap return value in a mirror object.");
#endif
ShouldNotReachHere();
return NULL;
}
void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
return Metaspace::allocate(loader_data, word_size, /*read_only*/false,
MetaspaceObj::ClassType, CHECK_NULL);
}
Klass::Klass() {
Klass* k = this;
// Preinitialize supertype information.
// A later call to initialize_supers() may update these settings:
set_super(NULL);
for (juint i = 0; i < Klass::primary_super_limit(); i++) {
_primary_supers[i] = NULL;
}
set_secondary_supers(NULL);
set_secondary_super_cache(NULL);
_primary_supers[0] = k;
set_super_check_offset(in_bytes(primary_supers_offset()));
set_java_mirror(NULL);
set_modifier_flags(0);
set_layout_helper(Klass::_lh_neutral_value);
set_name(NULL);
AccessFlags af;
af.set_flags(0);
set_access_flags(af);
set_subklass(NULL);
set_next_sibling(NULL);
set_next_link(NULL);
TRACE_INIT_ID(this);
set_prototype_header(markOopDesc::prototype());
set_biased_lock_revocation_count(0);
set_last_biased_lock_bulk_revocation_time(0);
// The klass doesn't have any references at this point.
clear_modified_oops();
clear_accumulated_modified_oops();
}
jint Klass::array_layout_helper(BasicType etype) {
assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
// Note that T_ARRAY is not allowed here.
int hsize = arrayOopDesc::base_offset_in_bytes(etype);
int esize = type2aelembytes(etype);
bool isobj = (etype == T_OBJECT);
int tag = isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));
assert(lh < (int)_lh_neutral_value, "must look like an array layout");
assert(layout_helper_is_array(lh), "correct kind");
assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
assert(layout_helper_header_size(lh) == hsize, "correct decode");
assert(layout_helper_element_type(lh) == etype, "correct decode");
assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
return lh;
}
bool Klass::can_be_primary_super_slow() const {
if (super() == NULL)
return true;
else if (super()->super_depth() >= primary_super_limit()-1)
return false;
else
return true;
}
void Klass::initialize_supers(Klass* k, TRAPS) {
if (FastSuperclassLimit == 0) {
// None of the other machinery matters.
set_super(k);
return;
}
if (k == NULL) {
set_super(NULL);
_primary_supers[0] = this;
assert(super_depth() == 0, "Object must already be initialized properly");
} else if (k != super() || k == SystemDictionary::Object_klass()) {
assert(super() == NULL || super() == SystemDictionary::Object_klass(),
"initialize this only once to a non-trivial value");
set_super(k);
Klass* sup = k;
int sup_depth = sup->super_depth();
juint my_depth = MIN2(sup_depth + 1, (int)primary_super_limit());
if (!can_be_primary_super_slow())
my_depth = primary_super_limit();
for (juint i = 0; i < my_depth; i++) {
_primary_supers[i] = sup->_primary_supers[i];
}
Klass* *super_check_cell;
if (my_depth < primary_super_limit()) {
_primary_supers[my_depth] = this;
super_check_cell = &_primary_supers[my_depth];
} else {
// Overflow of the primary_supers array forces me to be secondary.
super_check_cell = &_secondary_super_cache;
}
set_super_check_offset((address)super_check_cell - (address) this);
#ifdef ASSERT
{
juint j = super_depth();
assert(j == my_depth, "computed accessor gets right answer");
Klass* t = this;
while (!t->can_be_primary_super()) {
t = t->super();
j = t->super_depth();
}
for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
assert(primary_super_of_depth(j1) == NULL, "super list padding");
}
while (t != NULL) {
assert(primary_super_of_depth(j) == t, "super list initialization");
t = t->super();
--j;
}
assert(j == (juint)-1, "correct depth count");
}
#endif
}
if (secondary_supers() == NULL) {
KlassHandle this_kh (THREAD, this);
// Now compute the list of secondary supertypes.
// Secondaries can occasionally be on the super chain,
// if the inline "_primary_supers" array overflows.
int extras = 0;
Klass* p;
for (p = super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
++extras;
}
ResourceMark rm(THREAD); // need to reclaim GrowableArrays allocated below
// Compute the "real" non-extra secondaries.
GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras);
if (secondaries == NULL) {
// secondary_supers set by compute_secondary_supers
return;
}
GrowableArray<Klass*>* primaries = new GrowableArray(extras);
for (p = this_kh->super(); !(p == NULL || p->can_be_primary_super()); p = p->super()) {
int i; // Scan for overflow primaries being duplicates of 2nd'arys
// This happens frequently for very deeply nested arrays: the
// primary superclass chain overflows into the secondary. The
// secondary list contains the element_klass's secondaries with
// an extra array dimension added. If the element_klass's
// secondary list already contains some primary overflows, they
// (with the extra level of array-ness) will collide with the
// normal primary superclass overflows.
for( i = 0; i < secondaries->length(); i++ ) {
if( secondaries->at(i) == p )
break;
}
if( i < secondaries->length() )
continue; // It's a dup, don't put it in
primaries->push(p);
}
// Combine the two arrays into a metadata object to pack the array.
// The primaries are added in the reverse order, then the secondaries.
int new_length = primaries->length() + secondaries->length();
Array<Klass*>* s2 = MetadataFactory::new_array(
class_loader_data(), new_length, CHECK);
int fill_p = primaries->length();
for (int j = 0; j < fill_p; j++) {
s2->at_put(j, primaries->pop()); // add primaries in reverse order.
}
for( int j = 0; j < secondaries->length(); j++ ) {
s2->at_put(j+fill_p, secondaries->at(j)); // add secondaries on the end.
}
#ifdef ASSERT
// We must not copy any NULL placeholders left over from bootstrap.
for (int j = 0; j < s2->length(); j++) {
assert(s2->at(j) != NULL, "correct bootstrapping order");
}
#endif
this_kh->set_secondary_supers(s2);
}
}
GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots) {
assert(num_extra_slots == 0, "override for complex klasses");
set_secondary_supers(Universe::the_empty_klass_array());
return NULL;
}
Klass* Klass::subklass() const {
return _subklass == NULL ? NULL : _subklass;
}
InstanceKlass* Klass::superklass() const {
assert(super() == NULL || super()->oop_is_instance(), "must be instance klass");
return _super == NULL ? NULL : InstanceKlass::cast(_super);
}
Klass* Klass::next_sibling() const {
return _next_sibling == NULL ? NULL : _next_sibling;
}
void Klass::set_subklass(Klass* s) {
assert(s != this, "sanity check");
_subklass = s;
}
void Klass::set_next_sibling(Klass* s) {
assert(s != this, "sanity check");
_next_sibling = s;
}
void Klass::append_to_sibling_list() {
debug_only(verify();)
// add ourselves to superklass' subklass list
InstanceKlass* super = superklass();
if (super == NULL) return; // special case: class Object
assert((!super->is_interface() // interfaces cannot be supers
&& (super->superklass() == NULL || !is_interface())),
"an interface can only be a subklass of Object");
Klass* prev_first_subklass = super->subklass_oop();
if (prev_first_subklass != NULL) {
// set our sibling to be the superklass' previous first subklass
set_next_sibling(prev_first_subklass);
}
// make ourselves the superklass' first subklass
super->set_subklass(this);
debug_only(verify();)
}
bool Klass::is_loader_alive(BoolObjectClosure* is_alive) {
assert(ClassLoaderDataGraph::contains((address)this), "is in the metaspace");
#ifdef ASSERT
// The class is alive iff the class loader is alive.
oop loader = class_loader();
bool loader_alive = (loader == NULL) || is_alive->do_object_b(loader);
#endif // ASSERT
// The class is alive if it's mirror is alive (which should be marked if the
// loader is alive) unless it's an anoymous class.
bool mirror_alive = is_alive->do_object_b(java_mirror());
assert(!mirror_alive || loader_alive, "loader must be alive if the mirror is"
" but not the other way around with anonymous classes");
return mirror_alive;
}
void Klass::clean_weak_klass_links(BoolObjectClosure* is_alive) {
if (!ClassUnloading) {
return;
}
Klass* root = SystemDictionary::Object_klass();
Stack<Klass*, mtGC> stack;
stack.push(root);
while (!stack.is_empty()) {
Klass* current = stack.pop();
assert(current->is_loader_alive(is_alive), "just checking, this should be live");
// Find and set the first alive subklass
Klass* sub = current->subklass_oop();
while (sub != NULL && !sub->is_loader_alive(is_alive)) {
#ifndef PRODUCT
if (TraceClassUnloading && WizardMode) {
ResourceMark rm;
tty->print_cr("[Unlinking class (subclass) %s]", sub->external_name());
}
#endif
sub = sub->next_sibling_oop();
}
current->set_subklass(sub);
if (sub != NULL) {
stack.push(sub);
}
// Find and set the first alive sibling
Klass* sibling = current->next_sibling_oop();
while (sibling != NULL && !sibling->is_loader_alive(is_alive)) {
if (TraceClassUnloading && WizardMode) {
ResourceMark rm;
tty->print_cr("[Unlinking class (sibling) %s]", sibling->external_name());
}
sibling = sibling->next_sibling_oop();
}
current->set_next_sibling(sibling);
if (sibling != NULL) {
stack.push(sibling);
}
// Clean the implementors list and method data.
if (current->oop_is_instance()) {
InstanceKlass* ik = InstanceKlass::cast(current);
ik->clean_implementors_list(is_alive);
ik->clean_method_data(is_alive);
}
}
}
void Klass::klass_update_barrier_set(oop v) {
record_modified_oops();
}
void Klass::klass_update_barrier_set_pre(void* p, oop v) {
// This barrier used by G1, where it's used remember the old oop values,
// so that we don't forget any objects that were live at the snapshot at
// the beginning. This function is only used when we write oops into
// Klasses. Since the Klasses are used as roots in G1, we don't have to
// do anything here.
}
void Klass::klass_oop_store(oop* p, oop v) {
assert(!Universe::heap()->is_in_reserved((void*)p), "Should store pointer into metadata");
assert(v == NULL || Universe::heap()->is_in_reserved((void*)v), "Should store pointer to an object");
// do the store
if (always_do_update_barrier) {
klass_oop_store((volatile oop*)p, v);
} else {
klass_update_barrier_set_pre((void*)p, v);
*p = v;
klass_update_barrier_set(v);
}
}
void Klass::klass_oop_store(volatile oop* p, oop v) {
assert(!Universe::heap()->is_in_reserved((void*)p), "Should store pointer into metadata");
assert(v == NULL || Universe::heap()->is_in_reserved((void*)v), "Should store pointer to an object");
klass_update_barrier_set_pre((void*)p, v);
OrderAccess::release_store_ptr(p, v);
klass_update_barrier_set(v);
}
void Klass::oops_do(OopClosure* cl) {
cl->do_oop(&_java_mirror);
}
void Klass::remove_unshareable_info() {
if (!DumpSharedSpaces) {
// Clean up after OOM during class loading
if (class_loader_data() != NULL) {
class_loader_data()->remove_class(this);
}
}
set_subklass(NULL);
set_next_sibling(NULL);
// Clear the java mirror
set_java_mirror(NULL);
set_next_link(NULL);
// Null out class_loader_data because we don't share that yet.
set_class_loader_data(NULL);
}
void Klass::restore_unshareable_info(TRAPS) {
ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();
// Restore class_loader_data to the null class loader data
set_class_loader_data(loader_data);
// Add to null class loader list first before creating the mirror
// (same order as class file parsing)
loader_data->add_class(this);
// Recreate the class mirror. The protection_domain is always null for
// boot loader, for now.
java_lang_Class::create_mirror(this, Handle(NULL), CHECK);
}
Klass* Klass::array_klass_or_null(int rank) {
EXCEPTION_MARK;
// No exception can be thrown by array_klass_impl when called with or_null == true.
// (In anycase, the execption mark will fail if it do so)
return array_klass_impl(true, rank, THREAD);
}
Klass* Klass::array_klass_or_null() {
EXCEPTION_MARK;
// No exception can be thrown by array_klass_impl when called with or_null == true.
// (In anycase, the execption mark will fail if it do so)
return array_klass_impl(true, THREAD);
}
Klass* Klass::array_klass_impl(bool or_null, int rank, TRAPS) {
fatal("array_klass should be dispatched to InstanceKlass, ObjArrayKlass or TypeArrayKlass");
return NULL;
}
Klass* Klass::array_klass_impl(bool or_null, TRAPS) {
fatal("array_klass should be dispatched to InstanceKlass, ObjArrayKlass or TypeArrayKlass");
return NULL;
}
oop Klass::class_loader() const { return class_loader_data()->class_loader(); }
const char* Klass::external_name() const {
if (oop_is_instance()) {
InstanceKlass* ik = (InstanceKlass*) this;
if (ik->is_anonymous()) {
assert(EnableInvokeDynamic, "");
intptr_t hash = 0;
if (ik->java_mirror() != NULL) {
// java_mirror might not be created yet, return 0 as hash.
hash = ik->java_mirror()->identity_hash();
}
char hash_buf[40];
sprintf(hash_buf, "/" UINTX_FORMAT, (uintx)hash);
size_t hash_len = strlen(hash_buf);
size_t result_len = name()->utf8_length();
char* result = NEW_RESOURCE_ARRAY(char, result_len + hash_len + 1);
name()->as_klass_external_name(result, (int) result_len + 1);
assert(strlen(result) == result_len, "");
strcpy(result + result_len, hash_buf);
assert(strlen(result) == result_len + hash_len, "");
return result;
}
}
if (name() == NULL) return "<unknown>";
return name()->as_klass_external_name();
}
const char* Klass::signature_name() const {
if (name() == NULL) return "<unknown>";
return name()->as_C_string();
}
// Unless overridden, modifier_flags is 0.
jint Klass::compute_modifier_flags(TRAPS) const {
return 0;
}
int Klass::atomic_incr_biased_lock_revocation_count() {
return (int) Atomic::add(1, &_biased_lock_revocation_count);
}
// Unless overridden, jvmti_class_status has no flags set.
jint Klass::jvmti_class_status() const {
return 0;
}
// Printing
void Klass::print_on(outputStream* st) const {
ResourceMark rm;
// print title
st->print("%s", internal_name());
print_address_on(st);
st->cr();
}
void Klass::oop_print_on(oop obj, outputStream* st) {
ResourceMark rm;
// print title
st->print_cr("%s ", internal_name());
obj->print_address_on(st);
if (WizardMode) {
// print header
obj->mark()->print_on(st);
}
// print class
st->print(" - klass: ");
obj->klass()->print_value_on(st);
st->cr();
}
void Klass::oop_print_value_on(oop obj, outputStream* st) {
// print title
ResourceMark rm; // Cannot print in debug mode without this
st->print("%s", internal_name());
obj->print_address_on(st);
}
#if INCLUDE_SERVICES
// Size Statistics
void Klass::collect_statistics(KlassSizeStats *sz) const {
sz->_klass_bytes = sz->count(this);
sz->_mirror_bytes = sz->count(java_mirror());
sz->_secondary_supers_bytes = sz->count_array(secondary_supers());
sz->_ro_bytes += sz->_secondary_supers_bytes;
sz->_rw_bytes += sz->_klass_bytes + sz->_mirror_bytes;
}
#endif // INCLUDE_SERVICES
// Verification
void Klass::verify_on(outputStream* st, bool check_dictionary) {
// This can be expensive, but it is worth checking that this klass is actually
// in the CLD graph but not in production.
assert(ClassLoaderDataGraph::contains((address)this), "Should be");
guarantee(this->is_klass(),"should be klass");
if (super() != NULL) {
guarantee(super()->is_klass(), "should be klass");
}
if (secondary_super_cache() != NULL) {
Klass* ko = secondary_super_cache();
guarantee(ko->is_klass(), "should be klass");
}
for ( uint i = 0; i < primary_super_limit(); i++ ) {
Klass* ko = _primary_supers[i];
if (ko != NULL) {
guarantee(ko->is_klass(), "should be klass");
}
}
if (java_mirror() != NULL) {
guarantee(java_mirror()->is_oop(), "should be instance");
}
}
void Klass::oop_verify_on(oop obj, outputStream* st) {
guarantee(obj->is_oop(), "should be oop");
guarantee(obj->klass()->is_klass(), "klass field is not a klass");
}
#ifndef PRODUCT
bool Klass::verify_vtable_index(int i) {
if (oop_is_instance()) {
int limit = ((InstanceKlass*)this)->vtable_length()/vtableEntry::size();
assert(i >= 0 && i < limit, err_msg("index %d out of bounds %d", i, limit));
} else {
assert(oop_is_array(), "Must be");
int limit = ((ArrayKlass*)this)->vtable_length()/vtableEntry::size();
assert(i >= 0 && i < limit, err_msg("index %d out of bounds %d", i, limit));
}
return true;
}
bool Klass::verify_itable_index(int i) {
assert(oop_is_instance(), "");
int method_count = klassItable::method_count_for_interface(this);
assert(i >= 0 && i < method_count, "index out of bounds");
return true;
}
#endif
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