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/*
* Copyright (c) 1997, 2018, 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 "jvm.h"
#include "classfile/javaClasses.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "interpreter/linkResolver.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/metaspaceShared.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klassVtable.hpp"
#include "oops/method.hpp"
#include "oops/objArrayOop.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/arguments.hpp"
#include "runtime/flags/flagSetting.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/safepointVerifiers.hpp"
#include "utilities/copy.hpp"
inline InstanceKlass* klassVtable::ik() const {
return InstanceKlass::cast(_klass);
}
bool klassVtable::is_preinitialized_vtable() {
return _klass->is_shared() && !MetaspaceShared::remapped_readwrite();
}
// this function computes the vtable size (including the size needed for miranda
// methods) and the number of miranda methods in this class.
// Note on Miranda methods: Let's say there is a class C that implements
// interface I, and none of C's superclasses implements I.
// Let's say there is an abstract method m in I that neither C
// nor any of its super classes implement (i.e there is no method of any access,
// with the same name and signature as m), then m is a Miranda method which is
// entered as a public abstract method in C's vtable. From then on it should
// treated as any other public method in C for method over-ride purposes.
void klassVtable::compute_vtable_size_and_num_mirandas(
int* vtable_length_ret, int* num_new_mirandas,
GrowableArray<Method*>* all_mirandas, const Klass* super,
Array<Method*>* methods, AccessFlags class_flags, u2 major_version,
Handle classloader, Symbol* classname, Array<Klass*>* local_interfaces,
TRAPS) {
NoSafepointVerifier nsv;
// set up default result values
int vtable_length = 0;
// start off with super's vtable length
vtable_length = super == NULL ? 0 : super->vtable_length();
// go thru each method in the methods table to see if it needs a new entry
int len = methods->length();
for (int i = 0; i < len; i++) {
assert(methods->at(i)->is_method(), "must be a Method*");
methodHandle mh(THREAD, methods->at(i));
if (needs_new_vtable_entry(mh, super, classloader, classname, class_flags, major_version, THREAD)) {
vtable_length += vtableEntry::size(); // we need a new entry
}
}
GrowableArray<Method*> new_mirandas(20);
// compute the number of mirandas methods that must be added to the end
get_mirandas(&new_mirandas, all_mirandas, super, methods, NULL, local_interfaces,
class_flags.is_interface());
*num_new_mirandas = new_mirandas.length();
// Interfaces do not need interface methods in their vtables
// This includes miranda methods and during later processing, default methods
if (!class_flags.is_interface()) {
vtable_length += *num_new_mirandas * vtableEntry::size();
}
if (Universe::is_bootstrapping() && vtable_length == 0) {
// array classes don't have their superclass set correctly during
// bootstrapping
vtable_length = Universe::base_vtable_size();
}
if (super == NULL && vtable_length != Universe::base_vtable_size()) {
if (Universe::is_bootstrapping()) {
// Someone is attempting to override java.lang.Object incorrectly on the
// bootclasspath. The JVM cannot recover from this error including throwing
// an exception
vm_exit_during_initialization("Incompatible definition of java.lang.Object");
} else {
// Someone is attempting to redefine java.lang.Object incorrectly. The
// only way this should happen is from
// SystemDictionary::resolve_from_stream(), which will detect this later
// and throw a security exception. So don't assert here to let
// the exception occur.
vtable_length = Universe::base_vtable_size();
}
}
assert(vtable_length % vtableEntry::size() == 0, "bad vtable length");
assert(vtable_length >= Universe::base_vtable_size(), "vtable too small");
*vtable_length_ret = vtable_length;
}
int klassVtable::index_of(Method* m, int len) const {
assert(m->has_vtable_index(), "do not ask this of non-vtable methods");
return m->vtable_index();
}
// Copy super class's vtable to the first part (prefix) of this class's vtable,
// and return the number of entries copied. Expects that 'super' is the Java
// super class (arrays can have "array" super classes that must be skipped).
int klassVtable::initialize_from_super(Klass* super) {
if (super == NULL) {
return 0;
} else if (is_preinitialized_vtable()) {
// A shared class' vtable is preinitialized at dump time. No need to copy
// methods from super class for shared class, as that was already done
// during archiving time. However, if Jvmti has redefined a class,
// copy super class's vtable in case the super class has changed.
return super->vtable().length();
} else {
// copy methods from superKlass
klassVtable superVtable = super->vtable();
assert(superVtable.length() <= _length, "vtable too short");
#ifdef ASSERT
superVtable.verify(tty, true);
#endif
superVtable.copy_vtable_to(table());
if (log_develop_is_enabled(Trace, vtables)) {
ResourceMark rm;
log_develop_trace(vtables)("copy vtable from %s to %s size %d",
super->internal_name(), klass()->internal_name(),
_length);
}
return superVtable.length();
}
}
//
// Revised lookup semantics introduced 1.3 (Kestrel beta)
void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
// Note: Arrays can have intermediate array supers. Use java_super to skip them.
Klass* super = _klass->java_super();
int nofNewEntries = 0;
bool is_shared = _klass->is_shared();
if (!_klass->is_array_klass()) {
ResourceMark rm(THREAD);
log_develop_debug(vtables)("Initializing: %s", _klass->name()->as_C_string());
}
#ifdef ASSERT
oop* end_of_obj = (oop*)_klass + _klass->size();
oop* end_of_vtable = (oop*)&table()[_length];
assert(end_of_vtable <= end_of_obj, "vtable extends beyond end");
#endif
if (Universe::is_bootstrapping()) {
assert(!is_shared, "sanity");
// just clear everything
for (int i = 0; i < _length; i++) table()[i].clear();
return;
}
int super_vtable_len = initialize_from_super(super);
if (_klass->is_array_klass()) {
assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
} else {
assert(_klass->is_instance_klass(), "must be InstanceKlass");
Array<Method*>* methods = ik()->methods();
int len = methods->length();
int initialized = super_vtable_len;
// Check each of this class's methods against super;
// if override, replace in copy of super vtable, otherwise append to end
for (int i = 0; i < len; i++) {
// update_inherited_vtable can stop for gc - ensure using handles
HandleMark hm(THREAD);
assert(methods->at(i)->is_method(), "must be a Method*");
methodHandle mh(THREAD, methods->at(i));
bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, -1, checkconstraints, CHECK);
if (needs_new_entry) {
put_method_at(mh(), initialized);
mh()->set_vtable_index(initialized); // set primary vtable index
initialized++;
}
}
// update vtable with default_methods
Array<Method*>* default_methods = ik()->default_methods();
if (default_methods != NULL) {
len = default_methods->length();
if (len > 0) {
Array<int>* def_vtable_indices = NULL;
if ((def_vtable_indices = ik()->default_vtable_indices()) == NULL) {
assert(!is_shared, "shared class def_vtable_indices does not exist");
def_vtable_indices = ik()->create_new_default_vtable_indices(len, CHECK);
} else {
assert(def_vtable_indices->length() == len, "reinit vtable len?");
}
for (int i = 0; i < len; i++) {
HandleMark hm(THREAD);
assert(default_methods->at(i)->is_method(), "must be a Method*");
methodHandle mh(THREAD, default_methods->at(i));
assert(!mh->is_private(), "private interface method in the default method list");
bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, i, checkconstraints, CHECK);
// needs new entry
if (needs_new_entry) {
put_method_at(mh(), initialized);
if (is_preinitialized_vtable()) {
// At runtime initialize_vtable is rerun for a shared class
// (loaded by the non-boot loader) as part of link_class_impl().
// The dumptime vtable index should be the same as the runtime index.
assert(def_vtable_indices->at(i) == initialized,
"dump time vtable index is different from runtime index");
} else {
def_vtable_indices->at_put(i, initialized); //set vtable index
}
initialized++;
}
}
}
}
// add miranda methods; it will also return the updated initialized
// Interfaces do not need interface methods in their vtables
// This includes miranda methods and during later processing, default methods
if (!ik()->is_interface()) {
initialized = fill_in_mirandas(initialized);
}
// In class hierarchies where the accessibility is not increasing (i.e., going from private ->
// package_private -> public/protected), the vtable might actually be smaller than our initial
// calculation, for classfile versions for which we do not do transitive override
// calculations.
if (ik()->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
assert(initialized == _length, "vtable initialization failed");
} else {
assert(initialized <= _length, "vtable initialization failed");
for(;initialized < _length; initialized++) {
table()[initialized].clear();
}
}
NOT_PRODUCT(verify(tty, true));
}
}
// Called for cases where a method does not override its superclass' vtable entry
// For bytecodes not produced by javac together it is possible that a method does not override
// the superclass's method, but might indirectly override a super-super class's vtable entry
// If none found, return a null superk, else return the superk of the method this does override
// For public and protected methods: if they override a superclass, they will
// also be overridden themselves appropriately.
// Private methods do not override and are not overridden.
// Package Private methods are trickier:
// e.g. P1.A, pub m
// P2.B extends A, package private m
// P1.C extends B, public m
// P1.C.m needs to override P1.A.m and can not override P2.B.m
// Therefore: all package private methods need their own vtable entries for
// them to be the root of an inheritance overriding decision
// Package private methods may also override other vtable entries
InstanceKlass* klassVtable::find_transitive_override(InstanceKlass* initialsuper, const methodHandle& target_method,
int vtable_index, Handle target_loader, Symbol* target_classname, Thread * THREAD) {
InstanceKlass* superk = initialsuper;
while (superk != NULL && superk->super() != NULL) {
klassVtable ssVtable = (superk->super())->vtable();
if (vtable_index < ssVtable.length()) {
Method* super_method = ssVtable.method_at(vtable_index);
// get the class holding the matching method
// make sure you use that class for is_override
InstanceKlass* supermethodholder = super_method->method_holder();
#ifndef PRODUCT
Symbol* name= target_method()->name();
Symbol* signature = target_method()->signature();
assert(super_method->name() == name && super_method->signature() == signature, "vtable entry name/sig mismatch");
#endif
if (supermethodholder->is_override(super_method, target_loader, target_classname, THREAD)) {
if (log_develop_is_enabled(Trace, vtables)) {
ResourceMark rm(THREAD);
LogTarget(Trace, vtables) lt;
LogStream ls(lt);
char* sig = target_method()->name_and_sig_as_C_string();
ls.print("transitive overriding superclass %s with %s index %d, original flags: ",
supermethodholder->internal_name(),
sig, vtable_index);
super_method->print_linkage_flags(&ls);
ls.print("overriders flags: ");
target_method->print_linkage_flags(&ls);
ls.cr();
}
break; // return found superk
}
} else {
// super class has no vtable entry here, stop transitive search
superk = (InstanceKlass*)NULL;
break;
}
// if no override found yet, continue to search up
superk = superk->super() == NULL ? NULL : InstanceKlass::cast(superk->super());
}
return superk;
}
static void log_vtables(int i, bool overrides, const methodHandle& target_method,
Klass* target_klass, Method* super_method,
Thread* thread) {
#ifndef PRODUCT
if (log_develop_is_enabled(Trace, vtables)) {
ResourceMark rm(thread);
LogTarget(Trace, vtables) lt;
LogStream ls(lt);
char* sig = target_method()->name_and_sig_as_C_string();
if (overrides) {
ls.print("overriding with %s index %d, original flags: ",
sig, i);
} else {
ls.print("NOT overriding with %s index %d, original flags: ",
sig, i);
}
super_method->print_linkage_flags(&ls);
ls.print("overriders flags: ");
target_method->print_linkage_flags(&ls);
ls.cr();
}
#endif
}
// Update child's copy of super vtable for overrides
// OR return true if a new vtable entry is required.
// Only called for InstanceKlass's, i.e. not for arrays
// If that changed, could not use _klass as handle for klass
bool klassVtable::update_inherited_vtable(InstanceKlass* klass, const methodHandle& target_method,
int super_vtable_len, int default_index,
bool checkconstraints, TRAPS) {
ResourceMark rm;
bool allocate_new = true;
assert(klass->is_instance_klass(), "must be InstanceKlass");
Array<int>* def_vtable_indices = NULL;
bool is_default = false;
// default methods are non-private concrete methods in superinterfaces which are added
// to the vtable with their real method_holder.
// Since vtable and itable indices share the same storage, don't touch
// the default method's real vtable/itable index.
// default_vtable_indices stores the vtable value relative to this inheritor
if (default_index >= 0 ) {
is_default = true;
def_vtable_indices = klass->default_vtable_indices();
assert(!target_method()->is_private(), "private interface method flagged as default");
assert(def_vtable_indices != NULL, "def vtable alloc?");
assert(default_index <= def_vtable_indices->length(), "def vtable len?");
} else {
assert(klass == target_method()->method_holder(), "caller resp.");
// Initialize the method's vtable index to "nonvirtual".
// If we allocate a vtable entry, we will update it to a non-negative number.
target_method()->set_vtable_index(Method::nonvirtual_vtable_index);
}
// Static and <init> methods are never in
if (target_method()->is_static() || target_method()->name() == vmSymbols::object_initializer_name()) {
return false;
}
if (target_method->is_final_method(klass->access_flags())) {
// a final method never needs a new entry; final methods can be statically
// resolved and they have to be present in the vtable only if they override
// a super's method, in which case they re-use its entry
allocate_new = false;
} else if (klass->is_interface()) {
allocate_new = false; // see note below in needs_new_vtable_entry
// An interface never allocates new vtable slots, only inherits old ones.
// This method will either be assigned its own itable index later,
// or be assigned an inherited vtable index in the loop below.
// default methods inherited by classes store their vtable indices
// in the inheritor's default_vtable_indices.
// default methods inherited by interfaces may already have a
// valid itable index, if so, don't change it.
// Overpass methods in an interface will be assigned an itable index later
// by an inheriting class.
// Private interface methods have no itable index and are always invoked nonvirtually,
// so they retain their nonvirtual_vtable_index value, and therefore can_be_statically_bound()
// will return true.
if ((!is_default || !target_method()->has_itable_index()) && !target_method()->is_private()) {
target_method()->set_vtable_index(Method::pending_itable_index);
}
}
// we need a new entry if there is no superclass
Klass* super = klass->super();
if (super == NULL) {
return allocate_new;
}
// private methods in classes always have a new entry in the vtable
// specification interpretation since classic has
// private methods not overriding
// JDK8 adds private methods in interfaces which require invokespecial
if (target_method()->is_private()) {
return allocate_new;
}
// search through the vtable and update overridden entries
// Since check_signature_loaders acquires SystemDictionary_lock
// which can block for gc, once we are in this loop, use handles
// For classfiles built with >= jdk7, we now look for transitive overrides
Symbol* name = target_method()->name();
Symbol* signature = target_method()->signature();
Klass* target_klass = target_method()->method_holder();
if (target_klass == NULL) {
target_klass = _klass;
}
Handle target_loader(THREAD, target_klass->class_loader());
Symbol* target_classname = target_klass->name();
for(int i = 0; i < super_vtable_len; i++) {
Method* super_method;
if (is_preinitialized_vtable()) {
// If this is a shared class, the vtable is already in the final state (fully
// initialized). Need to look at the super's vtable.
klassVtable superVtable = super->vtable();
super_method = superVtable.method_at(i);
} else {
super_method = method_at(i);
}
// Check if method name matches. Ignore match if klass is an interface and the
// matching method is a non-public java.lang.Object method. (See JVMS 5.4.3.4)
// This is safe because the method at this slot should never get invoked.
// (TBD: put in a method to throw NoSuchMethodError if this slot is ever used.)
if (super_method->name() == name && super_method->signature() == signature &&
(!_klass->is_interface() ||
!SystemDictionary::is_nonpublic_Object_method(super_method))) {
// get super_klass for method_holder for the found method
InstanceKlass* super_klass = super_method->method_holder();
// Whether the method is being overridden
bool overrides = false;
// private methods are also never overridden
if (!super_method->is_private() &&
(is_default
|| ((super_klass->is_override(super_method, target_loader, target_classname, THREAD))
|| ((klass->major_version() >= VTABLE_TRANSITIVE_OVERRIDE_VERSION)
&& ((super_klass = find_transitive_override(super_klass,
target_method, i, target_loader,
target_classname, THREAD))
!= (InstanceKlass*)NULL)))))
{
// Package private methods always need a new entry to root their own
// overriding. They may also override other methods.
if (!target_method()->is_package_private()) {
allocate_new = false;
}
// Do not check loader constraints for overpass methods because overpass
// methods are created by the jvm to throw exceptions.
if (checkconstraints && !target_method()->is_overpass()) {
// Override vtable entry if passes loader constraint check
// if loader constraint checking requested
// No need to visit his super, since he and his super
// have already made any needed loader constraints.
// Since loader constraints are transitive, it is enough
// to link to the first super, and we get all the others.
Handle super_loader(THREAD, super_klass->class_loader());
if (!oopDesc::equals(target_loader(), super_loader())) {
ResourceMark rm(THREAD);
Symbol* failed_type_symbol =
SystemDictionary::check_signature_loaders(signature, target_loader,
super_loader, true,
CHECK_(false));
if (failed_type_symbol != NULL) {
stringStream ss;
ss.print("loader constraint violation for class %s: when selecting "
"overriding method '", klass->external_name());
target_method()->print_external_name(&ss),
ss.print("' the class loader %s of the "
"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 (%s; %s)",
target_klass->class_loader_data()->loader_name_and_id(),
target_klass->external_name(),
super_klass->class_loader_data()->loader_name_and_id(),
super_klass->external_name(),
failed_type_symbol->as_klass_external_name(),
target_klass->class_in_module_of_loader(false, true),
super_klass->class_in_module_of_loader(false, true));
THROW_MSG_(vmSymbols::java_lang_LinkageError(), ss.as_string(), false);
}
}
}
put_method_at(target_method(), i);
overrides = true;
if (!is_default) {
target_method()->set_vtable_index(i);
} else {
if (def_vtable_indices != NULL) {
if (is_preinitialized_vtable()) {
// At runtime initialize_vtable is rerun as part of link_class_impl()
// for a shared class loaded by the non-boot loader.
// The dumptime vtable index should be the same as the runtime index.
assert(def_vtable_indices->at(default_index) == i,
"dump time vtable index is different from runtime index");
} else {
def_vtable_indices->at_put(default_index, i);
}
}
assert(super_method->is_default_method() || super_method->is_overpass()
|| super_method->is_abstract(), "default override error");
}
} else {
overrides = false;
}
log_vtables(i, overrides, target_method, target_klass, super_method, THREAD);
}
}
return allocate_new;
}
void klassVtable::put_method_at(Method* m, int index) {
if (is_preinitialized_vtable()) {
// At runtime initialize_vtable is rerun as part of link_class_impl()
// for shared class loaded by the non-boot loader to obtain the loader
// constraints based on the runtime classloaders' context. The dumptime
// method at the vtable index should be the same as the runtime method.
assert(table()[index].method() == m,
"archived method is different from the runtime method");
} else {
if (log_develop_is_enabled(Trace, vtables)) {
ResourceMark rm;
LogTarget(Trace, vtables) lt;
LogStream ls(lt);
const char* sig = (m != NULL) ? m->name_and_sig_as_C_string() : "<NULL>";
ls.print("adding %s at index %d, flags: ", sig, index);
if (m != NULL) {
m->print_linkage_flags(&ls);
}
ls.cr();
}
table()[index].set(m);
}
}
// Find out if a method "m" with superclass "super", loader "classloader" and
// name "classname" needs a new vtable entry. Let P be a class package defined
// by "classloader" and "classname".
// NOTE: The logic used here is very similar to the one used for computing
// the vtables indices for a method. We cannot directly use that function because,
// we allocate the InstanceKlass at load time, and that requires that the
// superclass has been loaded.
// However, the vtable entries are filled in at link time, and therefore
// the superclass' vtable may not yet have been filled in.
bool klassVtable::needs_new_vtable_entry(const methodHandle& target_method,
const Klass* super,
Handle classloader,
Symbol* classname,
AccessFlags class_flags,
u2 major_version,
TRAPS) {
if (class_flags.is_interface()) {
// Interfaces do not use vtables, except for java.lang.Object methods,
// so there is no point to assigning
// a vtable index to any of their local methods. If we refrain from doing this,
// we can use Method::_vtable_index to hold the itable index
return false;
}
if (target_method->is_final_method(class_flags) ||
// a final method never needs a new entry; final methods can be statically
// resolved and they have to be present in the vtable only if they override
// a super's method, in which case they re-use its entry
(target_method()->is_static()) ||
// static methods don't need to be in vtable
(target_method()->name() == vmSymbols::object_initializer_name())
// <init> is never called dynamically-bound
) {
return false;
}
// Concrete interface methods do not need new entries, they override
// abstract method entries using default inheritance rules
if (target_method()->method_holder() != NULL &&
target_method()->method_holder()->is_interface() &&
!target_method()->is_abstract()) {
assert(target_method()->is_default_method() || target_method()->is_private(),
"unexpected interface method type");
return false;
}
// we need a new entry if there is no superclass
if (super == NULL) {
return true;
}
// private methods in classes always have a new entry in the vtable.
// Specification interpretation since classic has private methods not overriding.
if (target_method()->is_private()) {
return true;
}
// Package private methods always need a new entry to root their own
// overriding. This allows transitive overriding to work.
if (target_method()->is_package_private()) {
return true;
}
// search through the super class hierarchy to see if we need
// a new entry
ResourceMark rm(THREAD);
Symbol* name = target_method()->name();
Symbol* signature = target_method()->signature();
const Klass* k = super;
Method* super_method = NULL;
InstanceKlass *holder = NULL;
Method* recheck_method = NULL;
bool found_pkg_prvt_method = false;
while (k != NULL) {
// lookup through the hierarchy for a method with matching name and sign.
super_method = InstanceKlass::cast(k)->lookup_method(name, signature);
if (super_method == NULL) {
break; // we still have to search for a matching miranda method
}
// get the class holding the matching method
// make sure you use that class for is_override
InstanceKlass* superk = super_method->method_holder();
// we want only instance method matches
// pretend private methods are not in the super vtable
// since we do override around them: e.g. a.m pub/b.m private/c.m pub,
// ignore private, c.m pub does override a.m pub
// For classes that were not javac'd together, we also do transitive overriding around
// methods that have less accessibility
if ((!super_method->is_static()) &&
(!super_method->is_private())) {
if (superk->is_override(super_method, classloader, classname, THREAD)) {
return false;
// else keep looking for transitive overrides
}
// If we get here then one of the super classes has a package private method
// that will not get overridden because it is in a different package. But,
// that package private method does "override" any matching methods in super
// interfaces, so there will be no miranda vtable entry created. So, set flag
// to TRUE for use below, in case there are no methods in super classes that
// this target method overrides.
assert(super_method->is_package_private(), "super_method must be package private");
assert(!superk->is_same_class_package(classloader(), classname),
"Must be different packages");
found_pkg_prvt_method = true;
}
// Start with lookup result and continue to search up, for versions supporting transitive override
if (major_version >= VTABLE_TRANSITIVE_OVERRIDE_VERSION) {
k = superk->super(); // haven't found an override match yet; continue to look
} else {
break;
}
}
// If found_pkg_prvt_method is set, then the ONLY matching method in the
// superclasses is package private in another package. That matching method will
// prevent a miranda vtable entry from being created. Because the target method can not
// override the package private method in another package, then it needs to be the root
// for its own vtable entry.
if (found_pkg_prvt_method) {
return true;
}
// if the target method is public or protected it may have a matching
// miranda method in the super, whose entry it should re-use.
// Actually, to handle cases that javac would not generate, we need
// this check for all access permissions.
const InstanceKlass *sk = InstanceKlass::cast(super);
if (sk->has_miranda_methods()) {
if (sk->lookup_method_in_all_interfaces(name, signature, Klass::find_defaults) != NULL) {
return false; // found a matching miranda; we do not need a new entry
}
}
return true; // found no match; we need a new entry
}
// Support for miranda methods
// get the vtable index of a miranda method with matching "name" and "signature"
int klassVtable::index_of_miranda(Symbol* name, Symbol* signature) {
// search from the bottom, might be faster
for (int i = (length() - 1); i >= 0; i--) {
Method* m = table()[i].method();
if (is_miranda_entry_at(i) &&
m->name() == name && m->signature() == signature) {
return i;
}
}
return Method::invalid_vtable_index;
}
// check if an entry at an index is miranda
// requires that method m at entry be declared ("held") by an interface.
bool klassVtable::is_miranda_entry_at(int i) {
Method* m = method_at(i);
Klass* method_holder = m->method_holder();
InstanceKlass *mhk = InstanceKlass::cast(method_holder);
// miranda methods are public abstract instance interface methods in a class's vtable
if (mhk->is_interface()) {
assert(m->is_public(), "should be public");
assert(ik()->implements_interface(method_holder) , "this class should implement the interface");
if (is_miranda(m, ik()->methods(), ik()->default_methods(), ik()->super(), klass()->is_interface())) {
return true;
}
}
return false;
}
// Check if a method is a miranda method, given a class's methods array,
// its default_method table and its super class.
// "Miranda" means an abstract non-private method that would not be
// overridden for the local class.
// A "miranda" method should only include non-private interface
// instance methods, i.e. not private methods, not static methods,
// not default methods (concrete interface methods), not overpass methods.
// If a given class already has a local (including overpass) method, a
// default method, or any of its superclasses has the same which would have
// overridden an abstract method, then this is not a miranda method.
//
// Miranda methods are checked multiple times.
// Pass 1: during class load/class file parsing: before vtable size calculation:
// include superinterface abstract and default methods (non-private instance).
// We include potential default methods to give them space in the vtable.
// During the first run, the current instanceKlass has not yet been
// created, the superclasses and superinterfaces do have instanceKlasses
// but may not have vtables, the default_methods list is empty, no overpasses.
// Default method generation uses the all_mirandas array as the starter set for
// maximally-specific default method calculation. So, for both classes and
// interfaces, it is necessary that the first pass will find all non-private
// interface instance methods, whether or not they are concrete.
//
// Pass 2: recalculated during vtable initialization: only include abstract methods.
// The goal of pass 2 is to walk through the superinterfaces to see if any of
// the superinterface methods (which were all abstract pre-default methods)
// need to be added to the vtable.
// With the addition of default methods, we have three new challenges:
// overpasses, static interface methods and private interface methods.
// Static and private interface methods do not get added to the vtable and
// are not seen by the method resolution process, so we skip those.
// Overpass methods are already in the vtable, so vtable lookup will
// find them and we don't need to add a miranda method to the end of
// the vtable. So we look for overpass methods and if they are found we
// return false. Note that we inherit our superclasses vtable, so
// the superclass' search also needs to use find_overpass so that if
// one is found we return false.
// False means - we don't need a miranda method added to the vtable.
//
// During the second run, default_methods is set up, so concrete methods from
// superinterfaces with matching names/signatures to default_methods are already
// in the default_methods list and do not need to be appended to the vtable
// as mirandas. Abstract methods may already have been handled via
// overpasses - either local or superclass overpasses, which may be
// in the vtable already.
//
// Pass 3: They are also checked by link resolution and selection,
// for invocation on a method (not interface method) reference that
// resolves to a method with an interface as its method_holder.
// Used as part of walking from the bottom of the vtable to find
// the vtable index for the miranda method.
//
// Part of the Miranda Rights in the US mean that if you do not have
// an attorney one will be appointed for you.
bool klassVtable::is_miranda(Method* m, Array<Method*>* class_methods,
Array<Method*>* default_methods, const Klass* super,
bool is_interface) {
if (m->is_static() || m->is_private() || m->is_overpass()) {
return false;
}
Symbol* name = m->name();
Symbol* signature = m->signature();
// First look in local methods to see if already covered
if (InstanceKlass::find_local_method(class_methods, name, signature,
Klass::find_overpass, Klass::skip_static, Klass::skip_private) != NULL)
{
return false;
}
// Check local default methods
if ((default_methods != NULL) &&
(InstanceKlass::find_method(default_methods, name, signature) != NULL))
{
return false;
}
// Iterate on all superclasses, which should be InstanceKlasses.
// Note that we explicitly look for overpasses at each level.
// Overpasses may or may not exist for supers for pass 1,
// they should have been created for pass 2 and later.
for (const Klass* cursuper = super; cursuper != NULL; cursuper = cursuper->super())
{
Method* found_mth = InstanceKlass::cast(cursuper)->find_local_method(name, signature,
Klass::find_overpass, Klass::skip_static, Klass::skip_private);
// Ignore non-public methods in java.lang.Object if klass is an interface.
if (found_mth != NULL && (!is_interface ||
!SystemDictionary::is_nonpublic_Object_method(found_mth))) {
return false;
}
}
return true;
}
// Scans current_interface_methods for miranda methods that do not
// already appear in new_mirandas, or default methods, and are also not defined-and-non-private
// in super (superclass). These mirandas are added to all_mirandas if it is
// not null; in addition, those that are not duplicates of miranda methods
// inherited by super from its interfaces are added to new_mirandas.
// Thus, new_mirandas will be the set of mirandas that this class introduces,
// all_mirandas will be the set of all mirandas applicable to this class
// including all defined in superclasses.
void klassVtable::add_new_mirandas_to_lists(
GrowableArray<Method*>* new_mirandas, GrowableArray<Method*>* all_mirandas,
Array<Method*>* current_interface_methods, Array<Method*>* class_methods,
Array<Method*>* default_methods, const Klass* super, bool is_interface) {
// iterate thru the current interface's method to see if it a miranda
int num_methods = current_interface_methods->length();
for (int i = 0; i < num_methods; i++) {
Method* im = current_interface_methods->at(i);
bool is_duplicate = false;
int num_of_current_mirandas = new_mirandas->length();
// check for duplicate mirandas in different interfaces we implement
for (int j = 0; j < num_of_current_mirandas; j++) {
Method* miranda = new_mirandas->at(j);
if ((im->name() == miranda->name()) &&
(im->signature() == miranda->signature())) {
is_duplicate = true;
break;
}
}
if (!is_duplicate) { // we don't want duplicate miranda entries in the vtable
if (is_miranda(im, class_methods, default_methods, super, is_interface)) { // is it a miranda at all?
const InstanceKlass *sk = InstanceKlass::cast(super);
// check if it is a duplicate of a super's miranda
if (sk->lookup_method_in_all_interfaces(im->name(), im->signature(), Klass::find_defaults) == NULL) {
new_mirandas->append(im);
}
if (all_mirandas != NULL) {
all_mirandas->append(im);
}
}
}
}
}
void klassVtable::get_mirandas(GrowableArray<Method*>* new_mirandas,
GrowableArray<Method*>* all_mirandas,
const Klass* super,
Array<Method*>* class_methods,
Array<Method*>* default_methods,
Array<Klass*>* local_interfaces,
bool is_interface) {
assert((new_mirandas->length() == 0) , "current mirandas must be 0");
// iterate thru the local interfaces looking for a miranda
int num_local_ifs = local_interfaces->length();
for (int i = 0; i < num_local_ifs; i++) {
InstanceKlass *ik = InstanceKlass::cast(local_interfaces->at(i));
add_new_mirandas_to_lists(new_mirandas, all_mirandas,
ik->methods(), class_methods,
default_methods, super, is_interface);
// iterate thru each local's super interfaces
Array<Klass*>* super_ifs = ik->transitive_interfaces();
int num_super_ifs = super_ifs->length();
for (int j = 0; j < num_super_ifs; j++) {
InstanceKlass *sik = InstanceKlass::cast(super_ifs->at(j));
add_new_mirandas_to_lists(new_mirandas, all_mirandas,
sik->methods(), class_methods,
default_methods, super, is_interface);
}
}
}
// Discover miranda methods ("miranda" = "interface abstract, no binding"),
// and append them into the vtable starting at index initialized,
// return the new value of initialized.
// Miranda methods use vtable entries, but do not get assigned a vtable_index
// The vtable_index is discovered by searching from the end of the vtable
int klassVtable::fill_in_mirandas(int initialized) {
GrowableArray<Method*> mirandas(20);
get_mirandas(&mirandas, NULL, ik()->super(), ik()->methods(),
ik()->default_methods(), ik()->local_interfaces(),
klass()->is_interface());
for (int i = 0; i < mirandas.length(); i++) {
if (log_develop_is_enabled(Trace, vtables)) {
Method* meth = mirandas.at(i);
ResourceMark rm(Thread::current());
LogTarget(Trace, vtables) lt;
LogStream ls(lt);
if (meth != NULL) {
char* sig = meth->name_and_sig_as_C_string();
ls.print("fill in mirandas with %s index %d, flags: ",
sig, initialized);
meth->print_linkage_flags(&ls);
ls.cr();
}
}
put_method_at(mirandas.at(i), initialized);
++initialized;
}
return initialized;
}
// Copy this class's vtable to the vtable beginning at start.
// Used to copy superclass vtable to prefix of subclass's vtable.
void klassVtable::copy_vtable_to(vtableEntry* start) {
Copy::disjoint_words((HeapWord*)table(), (HeapWord*)start, _length * vtableEntry::size());
}
#if INCLUDE_JVMTI
bool klassVtable::adjust_default_method(int vtable_index, Method* old_method, Method* new_method) {
// If old_method is default, find this vtable index in default_vtable_indices
// and replace that method in the _default_methods list
bool updated = false;
Array<Method*>* default_methods = ik()->default_methods();
if (default_methods != NULL) {
int len = default_methods->length();
for (int idx = 0; idx < len; idx++) {
if (vtable_index == ik()->default_vtable_indices()->at(idx)) {
if (default_methods->at(idx) == old_method) {
default_methods->at_put(idx, new_method);
updated = true;
}
break;
}
}
}
return updated;
}
// search the vtable for uses of either obsolete or EMCP methods
void klassVtable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
int prn_enabled = 0;
for (int index = 0; index < length(); index++) {
Method* old_method = unchecked_method_at(index);
if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
continue; // skip uninteresting entries
}
assert(!old_method->is_deleted(), "vtable methods may not be deleted");
Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
assert(new_method != NULL, "method_with_idnum() should not be NULL");
assert(old_method != new_method, "sanity check");
put_method_at(new_method, index);
// For default methods, need to update the _default_methods array
// which can only have one method entry for a given signature
bool updated_default = false;
if (old_method->is_default_method()) {
updated_default = adjust_default_method(index, old_method, new_method);
}
if (log_is_enabled(Info, redefine, class, update)) {
ResourceMark rm;
if (!(*trace_name_printed)) {
log_info(redefine, class, update)
("adjust: klassname=%s for methods from name=%s",
_klass->external_name(), old_method->method_holder()->external_name());
*trace_name_printed = true;
}
log_debug(redefine, class, update, vtables)
("vtable method update: %s(%s), updated default = %s",
new_method->name()->as_C_string(), new_method->signature()->as_C_string(), updated_default ? "true" : "false");
}
}
}
// a vtable should never contain old or obsolete methods
bool klassVtable::check_no_old_or_obsolete_entries() {
for (int i = 0; i < length(); i++) {
Method* m = unchecked_method_at(i);
if (m != NULL &&
(NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
return false;
}
}
return true;
}
void klassVtable::dump_vtable() {
tty->print_cr("vtable dump --");
for (int i = 0; i < length(); i++) {
Method* m = unchecked_method_at(i);
if (m != NULL) {
tty->print(" (%5d) ", i);
m->access_flags().print_on(tty);
if (m->is_default_method()) {
tty->print("default ");
}
if (m->is_overpass()) {
tty->print("overpass");
}
tty->print(" -- ");
m->print_name(tty);
tty->cr();
}
}
}
#endif // INCLUDE_JVMTI
// CDS/RedefineClasses support - clear vtables so they can be reinitialized
void klassVtable::clear_vtable() {
for (int i = 0; i < _length; i++) table()[i].clear();
}
bool klassVtable::is_initialized() {
return _length == 0 || table()[0].method() != NULL;
}
//-----------------------------------------------------------------------------------------
// Itable code
// Initialize a itableMethodEntry
void itableMethodEntry::initialize(Method* m) {
if (m == NULL) return;
#ifdef ASSERT
if (MetaspaceShared::is_in_shared_metaspace((void*)&_method) &&
!MetaspaceShared::remapped_readwrite()) {
// At runtime initialize_itable is rerun as part of link_class_impl()
// for a shared class loaded by the non-boot loader.
// The dumptime itable method entry should be the same as the runtime entry.
assert(_method == m, "sanity");
}
#endif
_method = m;
}
klassItable::klassItable(InstanceKlass* klass) {
_klass = klass;
if (klass->itable_length() > 0) {
itableOffsetEntry* offset_entry = (itableOffsetEntry*)klass->start_of_itable();
if (offset_entry != NULL && offset_entry->interface_klass() != NULL) { // Check that itable is initialized
// First offset entry points to the first method_entry
intptr_t* method_entry = (intptr_t *)(((address)klass) + offset_entry->offset());
intptr_t* end = klass->end_of_itable();
_table_offset = (intptr_t*)offset_entry - (intptr_t*)klass;
_size_offset_table = (method_entry - ((intptr_t*)offset_entry)) / itableOffsetEntry::size();
_size_method_table = (end - method_entry) / itableMethodEntry::size();
assert(_table_offset >= 0 && _size_offset_table >= 0 && _size_method_table >= 0, "wrong computation");
return;
}
}
// The length of the itable was either zero, or it has not yet been initialized.
_table_offset = 0;
_size_offset_table = 0;
_size_method_table = 0;
}
static int initialize_count = 0;
// Initialization
void klassItable::initialize_itable(bool checkconstraints, TRAPS) {
if (_klass->is_interface()) {
// This needs to go after vtable indices are assigned but
// before implementors need to know the number of itable indices.
assign_itable_indices_for_interface(_klass);
}
// Cannot be setup doing bootstrapping, interfaces don't have
// itables, and klass with only ones entry have empty itables
if (Universe::is_bootstrapping() ||
_klass->is_interface() ||
_klass->itable_length() == itableOffsetEntry::size()) return;
// There's alway an extra itable entry so we can null-terminate it.
guarantee(size_offset_table() >= 1, "too small");
int num_interfaces = size_offset_table() - 1;
if (num_interfaces > 0) {
log_develop_debug(itables)("%3d: Initializing itables for %s", ++initialize_count,
_klass->name()->as_C_string());
// Iterate through all interfaces
int i;
for(i = 0; i < num_interfaces; i++) {
itableOffsetEntry* ioe = offset_entry(i);
HandleMark hm(THREAD);
Klass* interf = ioe->interface_klass();
assert(interf != NULL && ioe->offset() != 0, "bad offset entry in itable");
initialize_itable_for_interface(ioe->offset(), interf, checkconstraints, CHECK);
}
}
// Check that the last entry is empty
itableOffsetEntry* ioe = offset_entry(size_offset_table() - 1);
guarantee(ioe->interface_klass() == NULL && ioe->offset() == 0, "terminator entry missing");
}
inline bool interface_method_needs_itable_index(Method* m) {
if (m->is_static()) return false; // e.g., Stream.empty
if (m->is_initializer()) return false; // <init> or <clinit>
if (m->is_private()) return false; // uses direct call
// If an interface redeclares a method from java.lang.Object,
// it should already have a vtable index, don't touch it.
// e.g., CharSequence.toString (from initialize_vtable)
// if (m->has_vtable_index()) return false; // NO!
return true;
}
int klassItable::assign_itable_indices_for_interface(Klass* klass) {
// an interface does not have an itable, but its methods need to be numbered
log_develop_debug(itables)("%3d: Initializing itable indices for interface %s",
++initialize_count, klass->name()->as_C_string());
Array<Method*>* methods = InstanceKlass::cast(klass)->methods();
int nof_methods = methods->length();
int ime_num = 0;
for (int i = 0; i < nof_methods; i++) {
Method* m = methods->at(i);
if (interface_method_needs_itable_index(m)) {
assert(!m->is_final_method(), "no final interface methods");
// If m is already assigned a vtable index, do not disturb it.
if (log_develop_is_enabled(Trace, itables)) {
ResourceMark rm;
LogTarget(Trace, itables) lt;
LogStream ls(lt);
assert(m != NULL, "methods can never be null");
const char* sig = m->name_and_sig_as_C_string();
if (m->has_vtable_index()) {
ls.print("vtable index %d for method: %s, flags: ", m->vtable_index(), sig);
} else {
ls.print("itable index %d for method: %s, flags: ", ime_num, sig);
}
m->print_linkage_flags(&ls);
ls.cr();
}
if (!m->has_vtable_index()) {
// A shared method could have an initialized itable_index that
// is < 0.
assert(m->vtable_index() == Method::pending_itable_index ||
m->is_shared(),
"set by initialize_vtable");
m->set_itable_index(ime_num);
// Progress to next itable entry
ime_num++;
}
}
}
assert(ime_num == method_count_for_interface(klass), "proper sizing");
return ime_num;
}
int klassItable::method_count_for_interface(Klass* interf) {
assert(interf->is_instance_klass(), "must be");
assert(interf->is_interface(), "must be");
Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
int nof_methods = methods->length();
int length = 0;
while (nof_methods > 0) {
Method* m = methods->at(nof_methods-1);
if (m->has_itable_index()) {
length = m->itable_index() + 1;
break;
}
nof_methods -= 1;
}
#ifdef ASSERT
int nof_methods_copy = nof_methods;
while (nof_methods_copy > 0) {
Method* mm = methods->at(--nof_methods_copy);
assert(!mm->has_itable_index() || mm->itable_index() < length, "");
}
#endif //ASSERT
// return the rightmost itable index, plus one; or 0 if no methods have
// itable indices
return length;
}
void klassItable::initialize_itable_for_interface(int method_table_offset, Klass* interf, bool checkconstraints, TRAPS) {
Array<Method*>* methods = InstanceKlass::cast(interf)->methods();
int nof_methods = methods->length();
HandleMark hm;
Handle interface_loader (THREAD, InstanceKlass::cast(interf)->class_loader());
int ime_count = method_count_for_interface(interf);
for (int i = 0; i < nof_methods; i++) {
Method* m = methods->at(i);
methodHandle target;
if (m->has_itable_index()) {
// This search must match the runtime resolution, i.e. selection search for invokeinterface
// to correctly enforce loader constraints for interface method inheritance.
// Private methods are skipped as a private class method can never be the implementation
// of an interface method.
// Invokespecial does not perform selection based on the receiver, so it does not use
// the cached itable.
target = LinkResolver::lookup_instance_method_in_klasses(_klass, m->name(), m->signature(),
Klass::skip_private, CHECK);
}
if (target == NULL || !target->is_public() || target->is_abstract() || target->is_overpass()) {
assert(target == NULL || !target->is_overpass() || target->is_public(),
"Non-public overpass method!");
// Entry does not resolve. Leave it empty for AbstractMethodError or other error.
if (!(target == NULL) && !target->is_public()) {
// Stuff an IllegalAccessError throwing method in there instead.
itableOffsetEntry::method_entry(_klass, method_table_offset)[m->itable_index()].
initialize(Universe::throw_illegal_access_error());
}
} else {
// Entry did resolve, check loader constraints before initializing
// if checkconstraints requested
if (checkconstraints) {
Handle method_holder_loader (THREAD, target->method_holder()->class_loader());
if (!oopDesc::equals(method_holder_loader(), interface_loader())) {
ResourceMark rm(THREAD);
Symbol* failed_type_symbol =
SystemDictionary::check_signature_loaders(m->signature(),
method_holder_loader,
interface_loader,
true, CHECK);
if (failed_type_symbol != NULL) {
stringStream ss;
ss.print("loader constraint violation in interface itable"
" initialization for class %s: when selecting method '",
_klass->external_name());
m->print_external_name(&ss),
ss.print("' the class loader %s for super interface %s, and the class"
" loader %s of the selected method's %s, %s have"
" different Class objects for the type %s used in the signature (%s; %s)",
interf->class_loader_data()->loader_name_and_id(),
interf->external_name(),
target()->method_holder()->class_loader_data()->loader_name_and_id(),
target()->method_holder()->external_kind(),
target()->method_holder()->external_name(),
failed_type_symbol->as_klass_external_name(),
interf->class_in_module_of_loader(false, true),
target()->method_holder()->class_in_module_of_loader(false, true));
THROW_MSG(vmSymbols::java_lang_LinkageError(), ss.as_string());
}
}
}
// ime may have moved during GC so recalculate address
int ime_num = m->itable_index();
assert(ime_num < ime_count, "oob");
itableOffsetEntry::method_entry(_klass, method_table_offset)[ime_num].initialize(target());
if (log_develop_is_enabled(Trace, itables)) {
ResourceMark rm(THREAD);
if (target() != NULL) {
LogTarget(Trace, itables) lt;
LogStream ls(lt);
char* sig = target()->name_and_sig_as_C_string();
ls.print("interface: %s, ime_num: %d, target: %s, method_holder: %s ",
interf->internal_name(), ime_num, sig,
target()->method_holder()->internal_name());
ls.print("target_method flags: ");
target()->print_linkage_flags(&ls);
ls.cr();
}
}
}
}
}
#if INCLUDE_JVMTI
// search the itable for uses of either obsolete or EMCP methods
void klassItable::adjust_method_entries(InstanceKlass* holder, bool * trace_name_printed) {
itableMethodEntry* ime = method_entry(0);
for (int i = 0; i < _size_method_table; i++, ime++) {
Method* old_method = ime->method();
if (old_method == NULL || old_method->method_holder() != holder || !old_method->is_old()) {
continue; // skip uninteresting entries
}
assert(!old_method->is_deleted(), "itable methods may not be deleted");
Method* new_method = holder->method_with_idnum(old_method->orig_method_idnum());
assert(new_method != NULL, "method_with_idnum() should not be NULL");
assert(old_method != new_method, "sanity check");
ime->initialize(new_method);
if (log_is_enabled(Info, redefine, class, update)) {
ResourceMark rm;
if (!(*trace_name_printed)) {
log_info(redefine, class, update)("adjust: name=%s", old_method->method_holder()->external_name());
*trace_name_printed = true;
}
log_trace(redefine, class, update, itables)
("itable method update: %s(%s)", new_method->name()->as_C_string(), new_method->signature()->as_C_string());
}
}
}
// an itable should never contain old or obsolete methods
bool klassItable::check_no_old_or_obsolete_entries() {
itableMethodEntry* ime = method_entry(0);
for (int i = 0; i < _size_method_table; i++) {
Method* m = ime->method();
if (m != NULL &&
(NOT_PRODUCT(!m->is_valid() ||) m->is_old() || m->is_obsolete())) {
return false;
}
ime++;
}
return true;
}
void klassItable::dump_itable() {
itableMethodEntry* ime = method_entry(0);
tty->print_cr("itable dump --");
for (int i = 0; i < _size_method_table; i++) {
Method* m = ime->method();
if (m != NULL) {
tty->print(" (%5d) ", i);
m->access_flags().print_on(tty);
if (m->is_default_method()) {
tty->print("default ");
}
tty->print(" -- ");
m->print_name(tty);
tty->cr();
}
ime++;
}
}
#endif // INCLUDE_JVMTI
// Setup
class InterfaceVisiterClosure : public StackObj {
public:
virtual void doit(Klass* intf, int method_count) = 0;
};
// Visit all interfaces with at least one itable method
void visit_all_interfaces(Array<Klass*>* transitive_intf, InterfaceVisiterClosure *blk) {
// Handle array argument
for(int i = 0; i < transitive_intf->length(); i++) {
Klass* intf = transitive_intf->at(i);
assert(intf->is_interface(), "sanity check");
// Find no. of itable methods
int method_count = 0;
// method_count = klassItable::method_count_for_interface(intf);
Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
if (methods->length() > 0) {
for (int i = methods->length(); --i >= 0; ) {
if (interface_method_needs_itable_index(methods->at(i))) {
method_count++;
}
}
}
// Visit all interfaces which either have any methods or can participate in receiver type check.
// We do not bother to count methods in transitive interfaces, although that would allow us to skip
// this step in the rare case of a zero-method interface extending another zero-method interface.
if (method_count > 0 || InstanceKlass::cast(intf)->transitive_interfaces()->length() > 0) {
blk->doit(intf, method_count);
}
}
}
class CountInterfacesClosure : public InterfaceVisiterClosure {
private:
int _nof_methods;
int _nof_interfaces;
public:
CountInterfacesClosure() { _nof_methods = 0; _nof_interfaces = 0; }
int nof_methods() const { return _nof_methods; }
int nof_interfaces() const { return _nof_interfaces; }
void doit(Klass* intf, int method_count) { _nof_methods += method_count; _nof_interfaces++; }
};
class SetupItableClosure : public InterfaceVisiterClosure {
private:
itableOffsetEntry* _offset_entry;
itableMethodEntry* _method_entry;
address _klass_begin;
public:
SetupItableClosure(address klass_begin, itableOffsetEntry* offset_entry, itableMethodEntry* method_entry) {
_klass_begin = klass_begin;
_offset_entry = offset_entry;
_method_entry = method_entry;
}
itableMethodEntry* method_entry() const { return _method_entry; }
void doit(Klass* intf, int method_count) {
int offset = ((address)_method_entry) - _klass_begin;
_offset_entry->initialize(intf, offset);
_offset_entry++;
_method_entry += method_count;
}
};
int klassItable::compute_itable_size(Array<Klass*>* transitive_interfaces) {
// Count no of interfaces and total number of interface methods
CountInterfacesClosure cic;
visit_all_interfaces(transitive_interfaces, &cic);
// There's alway an extra itable entry so we can null-terminate it.
int itable_size = calc_itable_size(cic.nof_interfaces() + 1, cic.nof_methods());
// Statistics
update_stats(itable_size * wordSize);
return itable_size;
}
// Fill out offset table and interface klasses into the itable space
void klassItable::setup_itable_offset_table(InstanceKlass* klass) {
if (klass->itable_length() == 0) return;
assert(!klass->is_interface(), "Should have zero length itable");
// Count no of interfaces and total number of interface methods
CountInterfacesClosure cic;
visit_all_interfaces(klass->transitive_interfaces(), &cic);
int nof_methods = cic.nof_methods();
int nof_interfaces = cic.nof_interfaces();
// Add one extra entry so we can null-terminate the table
nof_interfaces++;
assert(compute_itable_size(klass->transitive_interfaces()) ==
calc_itable_size(nof_interfaces, nof_methods),
"mismatch calculation of itable size");
// Fill-out offset table
itableOffsetEntry* ioe = (itableOffsetEntry*)klass->start_of_itable();
itableMethodEntry* ime = (itableMethodEntry*)(ioe + nof_interfaces);
intptr_t* end = klass->end_of_itable();
assert((oop*)(ime + nof_methods) <= (oop*)klass->start_of_nonstatic_oop_maps(), "wrong offset calculation (1)");
assert((oop*)(end) == (oop*)(ime + nof_methods), "wrong offset calculation (2)");
// Visit all interfaces and initialize itable offset table
SetupItableClosure sic((address)klass, ioe, ime);
visit_all_interfaces(klass->transitive_interfaces(), &sic);
#ifdef ASSERT
ime = sic.method_entry();
oop* v = (oop*) klass->end_of_itable();
assert( (oop*)(ime) == v, "wrong offset calculation (2)");
#endif
}
// inverse to itable_index
Method* klassItable::method_for_itable_index(Klass* intf, int itable_index) {
assert(InstanceKlass::cast(intf)->is_interface(), "sanity check");
assert(intf->verify_itable_index(itable_index), "");
Array<Method*>* methods = InstanceKlass::cast(intf)->methods();
if (itable_index < 0 || itable_index >= method_count_for_interface(intf))
return NULL; // help caller defend against bad indices
int index = itable_index;
Method* m = methods->at(index);
int index2 = -1;
while (!m->has_itable_index() ||
(index2 = m->itable_index()) != itable_index) {
assert(index2 < itable_index, "monotonic");
if (++index == methods->length())
return NULL;
m = methods->at(index);
}
assert(m->itable_index() == itable_index, "correct inverse");
return m;
}
void klassVtable::verify(outputStream* st, bool forced) {
// make sure table is initialized
if (!Universe::is_fully_initialized()) return;
#ifndef PRODUCT
// avoid redundant verifies
if (!forced && _verify_count == Universe::verify_count()) return;
_verify_count = Universe::verify_count();
#endif
oop* end_of_obj = (oop*)_klass + _klass->size();
oop* end_of_vtable = (oop *)&table()[_length];
if (end_of_vtable > end_of_obj) {
fatal("klass %s: klass object too short (vtable extends beyond end)",
_klass->internal_name());
}
for (int i = 0; i < _length; i++) table()[i].verify(this, st);
// verify consistency with superKlass vtable
Klass* super = _klass->super();
if (super != NULL) {
InstanceKlass* sk = InstanceKlass::cast(super);
klassVtable vt = sk->vtable();
for (int i = 0; i < vt.length(); i++) {
verify_against(st, &vt, i);
}
}
}
void klassVtable::verify_against(outputStream* st, klassVtable* vt, int index) {
vtableEntry* vte = &vt->table()[index];
if (vte->method()->name() != table()[index].method()->name() ||
vte->method()->signature() != table()[index].method()->signature()) {
fatal("mismatched name/signature of vtable entries");
}
}
#ifndef PRODUCT
void klassVtable::print() {
ResourceMark rm;
tty->print("klassVtable for klass %s (length %d):\n", _klass->internal_name(), length());
for (int i = 0; i < length(); i++) {
table()[i].print();
tty->cr();
}
}
#endif
void vtableEntry::verify(klassVtable* vt, outputStream* st) {
NOT_PRODUCT(FlagSetting fs(IgnoreLockingAssertions, true));
Klass* vtklass = vt->klass();
if (vtklass->is_instance_klass() &&
(InstanceKlass::cast(vtklass)->major_version() >= klassVtable::VTABLE_TRANSITIVE_OVERRIDE_VERSION)) {
assert(method() != NULL, "must have set method");
}
if (method() != NULL) {
method()->verify();
// we sub_type, because it could be a miranda method
if (!vtklass->is_subtype_of(method()->method_holder())) {
#ifndef PRODUCT
print();
#endif
fatal("vtableEntry " PTR_FORMAT ": method is from subclass", p2i(this));
}
}
}
#ifndef PRODUCT
void vtableEntry::print() {
ResourceMark rm;
tty->print("vtableEntry %s: ", method()->name()->as_C_string());
if (Verbose) {
tty->print("m " PTR_FORMAT " ", p2i(method()));
}
}
class VtableStats : AllStatic {
public:
static int no_klasses; // # classes with vtables
static int no_array_klasses; // # array classes
static int no_instance_klasses; // # instanceKlasses
static int sum_of_vtable_len; // total # of vtable entries
static int sum_of_array_vtable_len; // total # of vtable entries in array klasses only
static int fixed; // total fixed overhead in bytes
static int filler; // overhead caused by filler bytes
static int entries; // total bytes consumed by vtable entries
static int array_entries; // total bytes consumed by array vtable entries
static void do_class(Klass* k) {
Klass* kl = k;
klassVtable vt = kl->vtable();
no_klasses++;
if (kl->is_instance_klass()) {
no_instance_klasses++;
kl->array_klasses_do(do_class);
}
if (kl->is_array_klass()) {
no_array_klasses++;
sum_of_array_vtable_len += vt.length();
}
sum_of_vtable_len += vt.length();
}
static void compute() {
ClassLoaderDataGraph::classes_do(do_class);
fixed = no_klasses * oopSize; // vtable length
// filler size is a conservative approximation
filler = oopSize * (no_klasses - no_instance_klasses) * (sizeof(InstanceKlass) - sizeof(ArrayKlass) - 1);
entries = sizeof(vtableEntry) * sum_of_vtable_len;
array_entries = sizeof(vtableEntry) * sum_of_array_vtable_len;
}
};
int VtableStats::no_klasses = 0;
int VtableStats::no_array_klasses = 0;
int VtableStats::no_instance_klasses = 0;
int VtableStats::sum_of_vtable_len = 0;
int VtableStats::sum_of_array_vtable_len = 0;
int VtableStats::fixed = 0;
int VtableStats::filler = 0;
int VtableStats::entries = 0;
int VtableStats::array_entries = 0;
void klassVtable::print_statistics() {
ResourceMark rm;
HandleMark hm;
VtableStats::compute();
tty->print_cr("vtable statistics:");
tty->print_cr("%6d classes (%d instance, %d array)", VtableStats::no_klasses, VtableStats::no_instance_klasses, VtableStats::no_array_klasses);
int total = VtableStats::fixed + VtableStats::filler + VtableStats::entries;
tty->print_cr("%6d bytes fixed overhead (refs + vtable object header)", VtableStats::fixed);
tty->print_cr("%6d bytes filler overhead", VtableStats::filler);
tty->print_cr("%6d bytes for vtable entries (%d for arrays)", VtableStats::entries, VtableStats::array_entries);
tty->print_cr("%6d bytes total", total);
}
int klassItable::_total_classes; // Total no. of classes with itables
long klassItable::_total_size; // Total no. of bytes used for itables
void klassItable::print_statistics() {
tty->print_cr("itable statistics:");
tty->print_cr("%6d classes with itables", _total_classes);
tty->print_cr("%6lu K uses for itables (average by class: %ld bytes)", _total_size / K, _total_size / _total_classes);
}
#endif // PRODUCT