8040237: nsk/jvmti/RetransformClasses/retransform001 crashed the VM on all platforms when run with with -server -Xcomp
Summary: class redefinition may cause speculative trap clean up code to dereference dead method
Reviewed-by: kvn, coleenp
/*
* Copyright (c) 2012, 2014, 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/bytecodeAssembler.hpp"
#include "classfile/defaultMethods.hpp"
#include "classfile/symbolTable.hpp"
#include "memory/allocation.hpp"
#include "memory/metadataFactory.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/signature.hpp"
#include "runtime/thread.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/klass.hpp"
#include "oops/method.hpp"
#include "utilities/accessFlags.hpp"
#include "utilities/exceptions.hpp"
#include "utilities/ostream.hpp"
#include "utilities/pair.hpp"
#include "utilities/resourceHash.hpp"
typedef enum { QUALIFIED, DISQUALIFIED } QualifiedState;
// Because we use an iterative algorithm when iterating over the type
// hierarchy, we can't use traditional scoped objects which automatically do
// cleanup in the destructor when the scope is exited. PseudoScope (and
// PseudoScopeMark) provides a similar functionality, but for when you want a
// scoped object in non-stack memory (such as in resource memory, as we do
// here). You've just got to remember to call 'destroy()' on the scope when
// leaving it (and marks have to be explicitly added).
class PseudoScopeMark : public ResourceObj {
public:
virtual void destroy() = 0;
};
class PseudoScope : public ResourceObj {
private:
GrowableArray<PseudoScopeMark*> _marks;
public:
static PseudoScope* cast(void* data) {
return static_cast<PseudoScope*>(data);
}
void add_mark(PseudoScopeMark* psm) {
_marks.append(psm);
}
void destroy() {
for (int i = 0; i < _marks.length(); ++i) {
_marks.at(i)->destroy();
}
}
};
#ifndef PRODUCT
static void print_slot(outputStream* str, Symbol* name, Symbol* signature) {
ResourceMark rm;
str->print("%s%s", name->as_C_string(), signature->as_C_string());
}
static void print_method(outputStream* str, Method* mo, bool with_class=true) {
ResourceMark rm;
if (with_class) {
str->print("%s.", mo->klass_name()->as_C_string());
}
print_slot(str, mo->name(), mo->signature());
}
#endif // ndef PRODUCT
/**
* Perform a depth-first iteration over the class hierarchy, applying
* algorithmic logic as it goes.
*
* This class is one half of the inheritance hierarchy analysis mechanism.
* It is meant to be used in conjunction with another class, the algorithm,
* which is indicated by the ALGO template parameter. This class can be
* paired with any algorithm class that provides the required methods.
*
* This class contains all the mechanics for iterating over the class hierarchy
* starting at a particular root, without recursing (thus limiting stack growth
* from this point). It visits each superclass (if present) and superinterface
* in a depth-first manner, with callbacks to the ALGO class as each class is
* encountered (visit()), The algorithm can cut-off further exploration of a
* particular branch by returning 'false' from a visit() call.
*
* The ALGO class, must provide a visit() method, which each of which will be
* called once for each node in the inheritance tree during the iteration. In
* addition, it can provide a memory block via new_node_data(InstanceKlass*),
* which it can use for node-specific storage (and access via the
* current_data() and data_at_depth(int) methods).
*
* Bare minimum needed to be an ALGO class:
* class Algo : public HierarchyVisitor<Algo> {
* void* new_node_data(InstanceKlass* cls) { return NULL; }
* void free_node_data(void* data) { return; }
* bool visit() { return true; }
* };
*/
template <class ALGO>
class HierarchyVisitor : StackObj {
private:
class Node : public ResourceObj {
public:
InstanceKlass* _class;
bool _super_was_visited;
int _interface_index;
void* _algorithm_data;
Node(InstanceKlass* cls, void* data, bool visit_super)
: _class(cls), _super_was_visited(!visit_super),
_interface_index(0), _algorithm_data(data) {}
int number_of_interfaces() { return _class->local_interfaces()->length(); }
int interface_index() { return _interface_index; }
void set_super_visited() { _super_was_visited = true; }
void increment_visited_interface() { ++_interface_index; }
void set_all_interfaces_visited() {
_interface_index = number_of_interfaces();
}
bool has_visited_super() { return _super_was_visited; }
bool has_visited_all_interfaces() {
return interface_index() >= number_of_interfaces();
}
InstanceKlass* interface_at(int index) {
return InstanceKlass::cast(_class->local_interfaces()->at(index));
}
InstanceKlass* next_super() { return _class->java_super(); }
InstanceKlass* next_interface() {
return interface_at(interface_index());
}
};
bool _cancelled;
GrowableArray<Node*> _path;
Node* current_top() const { return _path.top(); }
bool has_more_nodes() const { return !_path.is_empty(); }
void push(InstanceKlass* cls, void* data) {
assert(cls != NULL, "Requires a valid instance class");
Node* node = new Node(cls, data, has_super(cls));
_path.push(node);
}
void pop() { _path.pop(); }
void reset_iteration() {
_cancelled = false;
_path.clear();
}
bool is_cancelled() const { return _cancelled; }
// This code used to skip interface classes because their only
// superclass was j.l.Object which would be also covered by class
// superclass hierarchy walks. Now that the starting point can be
// an interface, we must ensure we catch j.l.Object as the super.
static bool has_super(InstanceKlass* cls) {
return cls->super() != NULL;
}
Node* node_at_depth(int i) const {
return (i >= _path.length()) ? NULL : _path.at(_path.length() - i - 1);
}
protected:
// Accessors available to the algorithm
int current_depth() const { return _path.length() - 1; }
InstanceKlass* class_at_depth(int i) {
Node* n = node_at_depth(i);
return n == NULL ? NULL : n->_class;
}
InstanceKlass* current_class() { return class_at_depth(0); }
void* data_at_depth(int i) {
Node* n = node_at_depth(i);
return n == NULL ? NULL : n->_algorithm_data;
}
void* current_data() { return data_at_depth(0); }
void cancel_iteration() { _cancelled = true; }
public:
void run(InstanceKlass* root) {
ALGO* algo = static_cast<ALGO*>(this);
reset_iteration();
void* algo_data = algo->new_node_data(root);
push(root, algo_data);
bool top_needs_visit = true;
do {
Node* top = current_top();
if (top_needs_visit) {
if (algo->visit() == false) {
// algorithm does not want to continue along this path. Arrange
// it so that this state is immediately popped off the stack
top->set_super_visited();
top->set_all_interfaces_visited();
}
top_needs_visit = false;
}
if (top->has_visited_super() && top->has_visited_all_interfaces()) {
algo->free_node_data(top->_algorithm_data);
pop();
} else {
InstanceKlass* next = NULL;
if (top->has_visited_super() == false) {
next = top->next_super();
top->set_super_visited();
} else {
next = top->next_interface();
top->increment_visited_interface();
}
assert(next != NULL, "Otherwise we shouldn't be here");
algo_data = algo->new_node_data(next);
push(next, algo_data);
top_needs_visit = true;
}
} while (!is_cancelled() && has_more_nodes());
}
};
#ifndef PRODUCT
class PrintHierarchy : public HierarchyVisitor<PrintHierarchy> {
public:
bool visit() {
InstanceKlass* cls = current_class();
streamIndentor si(tty, current_depth() * 2);
tty->indent().print_cr("%s", cls->name()->as_C_string());
return true;
}
void* new_node_data(InstanceKlass* cls) { return NULL; }
void free_node_data(void* data) { return; }
};
#endif // ndef PRODUCT
// Used to register InstanceKlass objects and all related metadata structures
// (Methods, ConstantPools) as "in-use" by the current thread so that they can't
// be deallocated by class redefinition while we're using them. The classes are
// de-registered when this goes out of scope.
//
// Once a class is registered, we need not bother with methodHandles or
// constantPoolHandles for it's associated metadata.
class KeepAliveRegistrar : public StackObj {
private:
Thread* _thread;
GrowableArray<ConstantPool*> _keep_alive;
public:
KeepAliveRegistrar(Thread* thread) : _thread(thread), _keep_alive(20) {
assert(thread == Thread::current(), "Must be current thread");
}
~KeepAliveRegistrar() {
for (int i = _keep_alive.length() - 1; i >= 0; --i) {
ConstantPool* cp = _keep_alive.at(i);
int idx = _thread->metadata_handles()->find_from_end(cp);
assert(idx > 0, "Must be in the list");
_thread->metadata_handles()->remove_at(idx);
}
}
// Register a class as 'in-use' by the thread. It's fine to register a class
// multiple times (though perhaps inefficient)
void register_class(InstanceKlass* ik) {
ConstantPool* cp = ik->constants();
_keep_alive.push(cp);
_thread->metadata_handles()->push(cp);
}
};
class KeepAliveVisitor : public HierarchyVisitor<KeepAliveVisitor> {
private:
KeepAliveRegistrar* _registrar;
public:
KeepAliveVisitor(KeepAliveRegistrar* registrar) : _registrar(registrar) {}
void* new_node_data(InstanceKlass* cls) { return NULL; }
void free_node_data(void* data) { return; }
bool visit() {
_registrar->register_class(current_class());
return true;
}
};
// A method family contains a set of all methods that implement a single
// erased method. As members of the set are collected while walking over the
// hierarchy, they are tagged with a qualification state. The qualification
// state for an erased method is set to disqualified if there exists a path
// from the root of hierarchy to the method that contains an interleaving
// erased method defined in an interface.
class MethodFamily : public ResourceObj {
private:
GrowableArray<Pair<Method*,QualifiedState> > _members;
ResourceHashtable<Method*, int> _member_index;
Method* _selected_target; // Filled in later, if a unique target exists
Symbol* _exception_message; // If no unique target is found
Symbol* _exception_name; // If no unique target is found
bool contains_method(Method* method) {
int* lookup = _member_index.get(method);
return lookup != NULL;
}
void add_method(Method* method, QualifiedState state) {
Pair<Method*,QualifiedState> entry(method, state);
_member_index.put(method, _members.length());
_members.append(entry);
}
void disqualify_method(Method* method) {
int* index = _member_index.get(method);
guarantee(index != NULL && *index >= 0 && *index < _members.length(), "bad index");
_members.at(*index).second = DISQUALIFIED;
}
Symbol* generate_no_defaults_message(TRAPS) const;
Symbol* generate_method_message(Symbol *klass_name, Method* method, TRAPS) const;
Symbol* generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const;
public:
MethodFamily()
: _selected_target(NULL), _exception_message(NULL), _exception_name(NULL) {}
void set_target_if_empty(Method* m) {
if (_selected_target == NULL && !m->is_overpass()) {
_selected_target = m;
}
}
void record_qualified_method(Method* m) {
// If the method already exists in the set as qualified, this operation is
// redundant. If it already exists as disqualified, then we leave it as
// disqualfied. Thus we only add to the set if it's not already in the
// set.
if (!contains_method(m)) {
add_method(m, QUALIFIED);
}
}
void record_disqualified_method(Method* m) {
// If not in the set, add it as disqualified. If it's already in the set,
// then set the state to disqualified no matter what the previous state was.
if (!contains_method(m)) {
add_method(m, DISQUALIFIED);
} else {
disqualify_method(m);
}
}
bool has_target() const { return _selected_target != NULL; }
bool throws_exception() { return _exception_message != NULL; }
Method* get_selected_target() { return _selected_target; }
Symbol* get_exception_message() { return _exception_message; }
Symbol* get_exception_name() { return _exception_name; }
// Either sets the target or the exception error message
void determine_target(InstanceKlass* root, TRAPS) {
if (has_target() || throws_exception()) {
return;
}
// Qualified methods are maximally-specific methods
// These include public, instance concrete (=default) and abstract methods
GrowableArray<Method*> qualified_methods;
int num_defaults = 0;
int default_index = -1;
int qualified_index = -1;
for (int i = 0; i < _members.length(); ++i) {
Pair<Method*,QualifiedState> entry = _members.at(i);
if (entry.second == QUALIFIED) {
qualified_methods.append(entry.first);
qualified_index++;
if (entry.first->is_default_method()) {
num_defaults++;
default_index = qualified_index;
}
}
}
if (num_defaults == 0) {
// If the root klass has a static method with matching name and signature
// then do not generate an overpass method because it will hide the
// static method during resolution.
if (qualified_methods.length() == 0) {
_exception_message = generate_no_defaults_message(CHECK);
} else {
assert(root != NULL, "Null root class");
_exception_message = generate_method_message(root->name(), qualified_methods.at(0), CHECK);
}
_exception_name = vmSymbols::java_lang_AbstractMethodError();
// If only one qualified method is default, select that
} else if (num_defaults == 1) {
_selected_target = qualified_methods.at(default_index);
} else if (num_defaults > 1) {
_exception_message = generate_conflicts_message(&qualified_methods,CHECK);
_exception_name = vmSymbols::java_lang_IncompatibleClassChangeError();
if (TraceDefaultMethods) {
_exception_message->print_value_on(tty);
tty->cr();
}
}
}
bool contains_signature(Symbol* query) {
for (int i = 0; i < _members.length(); ++i) {
if (query == _members.at(i).first->signature()) {
return true;
}
}
return false;
}
#ifndef PRODUCT
void print_sig_on(outputStream* str, Symbol* signature, int indent) const {
streamIndentor si(str, indent * 2);
str->indent().print_cr("Logical Method %s:", signature->as_C_string());
streamIndentor si2(str);
for (int i = 0; i < _members.length(); ++i) {
str->indent();
print_method(str, _members.at(i).first);
if (_members.at(i).second == DISQUALIFIED) {
str->print(" (disqualified)");
}
str->cr();
}
if (_selected_target != NULL) {
print_selected(str, 1);
}
}
void print_selected(outputStream* str, int indent) const {
assert(has_target(), "Should be called otherwise");
streamIndentor si(str, indent * 2);
str->indent().print("Selected method: ");
print_method(str, _selected_target);
Klass* method_holder = _selected_target->method_holder();
if (!method_holder->is_interface()) {
tty->print(" : in superclass");
}
str->cr();
}
void print_exception(outputStream* str, int indent) {
assert(throws_exception(), "Should be called otherwise");
assert(_exception_name != NULL, "exception_name should be set");
streamIndentor si(str, indent * 2);
str->indent().print_cr("%s: %s", _exception_name->as_C_string(), _exception_message->as_C_string());
}
#endif // ndef PRODUCT
};
Symbol* MethodFamily::generate_no_defaults_message(TRAPS) const {
return SymbolTable::new_symbol("No qualifying defaults found", CHECK_NULL);
}
Symbol* MethodFamily::generate_method_message(Symbol *klass_name, Method* method, TRAPS) const {
stringStream ss;
ss.print("Method ");
Symbol* name = method->name();
Symbol* signature = method->signature();
ss.write((const char*)klass_name->bytes(), klass_name->utf8_length());
ss.print(".");
ss.write((const char*)name->bytes(), name->utf8_length());
ss.write((const char*)signature->bytes(), signature->utf8_length());
ss.print(" is abstract");
return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);
}
Symbol* MethodFamily::generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const {
stringStream ss;
ss.print("Conflicting default methods:");
for (int i = 0; i < methods->length(); ++i) {
Method* method = methods->at(i);
Symbol* klass = method->klass_name();
Symbol* name = method->name();
ss.print(" ");
ss.write((const char*)klass->bytes(), klass->utf8_length());
ss.print(".");
ss.write((const char*)name->bytes(), name->utf8_length());
}
return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);
}
class StateRestorer;
// StatefulMethodFamily is a wrapper around a MethodFamily that maintains the
// qualification state during hierarchy visitation, and applies that state
// when adding members to the MethodFamily
class StatefulMethodFamily : public ResourceObj {
friend class StateRestorer;
private:
QualifiedState _qualification_state;
void set_qualification_state(QualifiedState state) {
_qualification_state = state;
}
protected:
MethodFamily* _method_family;
public:
StatefulMethodFamily() {
_method_family = new MethodFamily();
_qualification_state = QUALIFIED;
}
StatefulMethodFamily(MethodFamily* mf) {
_method_family = mf;
_qualification_state = QUALIFIED;
}
void set_target_if_empty(Method* m) { _method_family->set_target_if_empty(m); }
MethodFamily* get_method_family() { return _method_family; }
StateRestorer* record_method_and_dq_further(Method* mo);
};
class StateRestorer : public PseudoScopeMark {
private:
StatefulMethodFamily* _method;
QualifiedState _state_to_restore;
public:
StateRestorer(StatefulMethodFamily* dm, QualifiedState state)
: _method(dm), _state_to_restore(state) {}
~StateRestorer() { destroy(); }
void restore_state() { _method->set_qualification_state(_state_to_restore); }
virtual void destroy() { restore_state(); }
};
StateRestorer* StatefulMethodFamily::record_method_and_dq_further(Method* mo) {
StateRestorer* mark = new StateRestorer(this, _qualification_state);
if (_qualification_state == QUALIFIED) {
_method_family->record_qualified_method(mo);
} else {
_method_family->record_disqualified_method(mo);
}
// Everything found "above"??? this method in the hierarchy walk is set to
// disqualified
set_qualification_state(DISQUALIFIED);
return mark;
}
// Represents a location corresponding to a vtable slot for methods that
// neither the class nor any of it's ancestors provide an implementaion.
// Default methods may be present to fill this slot.
class EmptyVtableSlot : public ResourceObj {
private:
Symbol* _name;
Symbol* _signature;
int _size_of_parameters;
MethodFamily* _binding;
public:
EmptyVtableSlot(Method* method)
: _name(method->name()), _signature(method->signature()),
_size_of_parameters(method->size_of_parameters()), _binding(NULL) {}
Symbol* name() const { return _name; }
Symbol* signature() const { return _signature; }
int size_of_parameters() const { return _size_of_parameters; }
void bind_family(MethodFamily* lm) { _binding = lm; }
bool is_bound() { return _binding != NULL; }
MethodFamily* get_binding() { return _binding; }
#ifndef PRODUCT
void print_on(outputStream* str) const {
print_slot(str, name(), signature());
}
#endif // ndef PRODUCT
};
static bool already_in_vtable_slots(GrowableArray<EmptyVtableSlot*>* slots, Method* m) {
bool found = false;
for (int j = 0; j < slots->length(); ++j) {
if (slots->at(j)->name() == m->name() &&
slots->at(j)->signature() == m->signature() ) {
found = true;
break;
}
}
return found;
}
static GrowableArray<EmptyVtableSlot*>* find_empty_vtable_slots(
InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {
assert(klass != NULL, "Must be valid class");
GrowableArray<EmptyVtableSlot*>* slots = new GrowableArray<EmptyVtableSlot*>();
// All miranda methods are obvious candidates
for (int i = 0; i < mirandas->length(); ++i) {
Method* m = mirandas->at(i);
if (!already_in_vtable_slots(slots, m)) {
slots->append(new EmptyVtableSlot(m));
}
}
// Also any overpasses in our superclasses, that we haven't implemented.
// (can't use the vtable because it is not guaranteed to be initialized yet)
InstanceKlass* super = klass->java_super();
while (super != NULL) {
for (int i = 0; i < super->methods()->length(); ++i) {
Method* m = super->methods()->at(i);
if (m->is_overpass() || m->is_static()) {
// m is a method that would have been a miranda if not for the
// default method processing that occurred on behalf of our superclass,
// so it's a method we want to re-examine in this new context. That is,
// unless we have a real implementation of it in the current class.
Method* impl = klass->lookup_method(m->name(), m->signature());
if (impl == NULL || impl->is_overpass() || impl->is_static()) {
if (!already_in_vtable_slots(slots, m)) {
slots->append(new EmptyVtableSlot(m));
}
}
}
}
// also any default methods in our superclasses
if (super->default_methods() != NULL) {
for (int i = 0; i < super->default_methods()->length(); ++i) {
Method* m = super->default_methods()->at(i);
// m is a method that would have been a miranda if not for the
// default method processing that occurred on behalf of our superclass,
// so it's a method we want to re-examine in this new context. That is,
// unless we have a real implementation of it in the current class.
Method* impl = klass->lookup_method(m->name(), m->signature());
if (impl == NULL || impl->is_overpass() || impl->is_static()) {
if (!already_in_vtable_slots(slots, m)) {
slots->append(new EmptyVtableSlot(m));
}
}
}
}
super = super->java_super();
}
#ifndef PRODUCT
if (TraceDefaultMethods) {
tty->print_cr("Slots that need filling:");
streamIndentor si(tty);
for (int i = 0; i < slots->length(); ++i) {
tty->indent();
slots->at(i)->print_on(tty);
tty->cr();
}
}
#endif // ndef PRODUCT
return slots;
}
// Iterates over the superinterface type hierarchy looking for all methods
// with a specific erased signature.
class FindMethodsByErasedSig : public HierarchyVisitor<FindMethodsByErasedSig> {
private:
// Context data
Symbol* _method_name;
Symbol* _method_signature;
StatefulMethodFamily* _family;
public:
FindMethodsByErasedSig(Symbol* name, Symbol* signature) :
_method_name(name), _method_signature(signature),
_family(NULL) {}
void get_discovered_family(MethodFamily** family) {
if (_family != NULL) {
*family = _family->get_method_family();
} else {
*family = NULL;
}
}
void* new_node_data(InstanceKlass* cls) { return new PseudoScope(); }
void free_node_data(void* node_data) {
PseudoScope::cast(node_data)->destroy();
}
// Find all methods on this hierarchy that match this
// method's erased (name, signature)
bool visit() {
PseudoScope* scope = PseudoScope::cast(current_data());
InstanceKlass* iklass = current_class();
Method* m = iklass->find_method(_method_name, _method_signature);
// private interface methods are not candidates for default methods
// invokespecial to private interface methods doesn't use default method logic
// The overpasses are your supertypes' errors, we do not include them
// future: take access controls into account for superclass methods
if (m != NULL && !m->is_static() && !m->is_overpass() &&
(!iklass->is_interface() || m->is_public())) {
if (_family == NULL) {
_family = new StatefulMethodFamily();
}
if (iklass->is_interface()) {
StateRestorer* restorer = _family->record_method_and_dq_further(m);
scope->add_mark(restorer);
} else {
// This is the rule that methods in classes "win" (bad word) over
// methods in interfaces. This works because of single inheritance
_family->set_target_if_empty(m);
}
}
return true;
}
};
static void create_defaults_and_exceptions(
GrowableArray<EmptyVtableSlot*>* slots, InstanceKlass* klass, TRAPS);
static void generate_erased_defaults(
InstanceKlass* klass, GrowableArray<EmptyVtableSlot*>* empty_slots,
EmptyVtableSlot* slot, TRAPS) {
// sets up a set of methods with the same exact erased signature
FindMethodsByErasedSig visitor(slot->name(), slot->signature());
visitor.run(klass);
MethodFamily* family;
visitor.get_discovered_family(&family);
if (family != NULL) {
family->determine_target(klass, CHECK);
slot->bind_family(family);
}
}
static void merge_in_new_methods(InstanceKlass* klass,
GrowableArray<Method*>* new_methods, TRAPS);
static void create_default_methods( InstanceKlass* klass,
GrowableArray<Method*>* new_methods, TRAPS);
// This is the guts of the default methods implementation. This is called just
// after the classfile has been parsed if some ancestor has default methods.
//
// First if finds any name/signature slots that need any implementation (either
// because they are miranda or a superclass's implementation is an overpass
// itself). For each slot, iterate over the hierarchy, to see if they contain a
// signature that matches the slot we are looking at.
//
// For each slot filled, we generate an overpass method that either calls the
// unique default method candidate using invokespecial, or throws an exception
// (in the case of no default method candidates, or more than one valid
// candidate). These methods are then added to the class's method list.
// The JVM does not create bridges nor handle generic signatures here.
void DefaultMethods::generate_default_methods(
InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {
// This resource mark is the bound for all memory allocation that takes
// place during default method processing. After this goes out of scope,
// all (Resource) objects' memory will be reclaimed. Be careful if adding an
// embedded resource mark under here as that memory can't be used outside
// whatever scope it's in.
ResourceMark rm(THREAD);
// Keep entire hierarchy alive for the duration of the computation
KeepAliveRegistrar keepAlive(THREAD);
KeepAliveVisitor loadKeepAlive(&keepAlive);
loadKeepAlive.run(klass);
#ifndef PRODUCT
if (TraceDefaultMethods) {
ResourceMark rm; // be careful with these!
tty->print_cr("%s %s requires default method processing",
klass->is_interface() ? "Interface" : "Class",
klass->name()->as_klass_external_name());
PrintHierarchy printer;
printer.run(klass);
}
#endif // ndef PRODUCT
GrowableArray<EmptyVtableSlot*>* empty_slots =
find_empty_vtable_slots(klass, mirandas, CHECK);
for (int i = 0; i < empty_slots->length(); ++i) {
EmptyVtableSlot* slot = empty_slots->at(i);
#ifndef PRODUCT
if (TraceDefaultMethods) {
streamIndentor si(tty, 2);
tty->indent().print("Looking for default methods for slot ");
slot->print_on(tty);
tty->cr();
}
#endif // ndef PRODUCT
generate_erased_defaults(klass, empty_slots, slot, CHECK);
}
#ifndef PRODUCT
if (TraceDefaultMethods) {
tty->print_cr("Creating defaults and overpasses...");
}
#endif // ndef PRODUCT
create_defaults_and_exceptions(empty_slots, klass, CHECK);
#ifndef PRODUCT
if (TraceDefaultMethods) {
tty->print_cr("Default method processing complete");
}
#endif // ndef PRODUCT
}
static int assemble_method_error(
BytecodeConstantPool* cp, BytecodeBuffer* buffer, Symbol* errorName, Symbol* message, TRAPS) {
Symbol* init = vmSymbols::object_initializer_name();
Symbol* sig = vmSymbols::string_void_signature();
BytecodeAssembler assem(buffer, cp);
assem._new(errorName);
assem.dup();
assem.load_string(message);
assem.invokespecial(errorName, init, sig);
assem.athrow();
return 3; // max stack size: [ exception, exception, string ]
}
static Method* new_method(
BytecodeConstantPool* cp, BytecodeBuffer* bytecodes, Symbol* name,
Symbol* sig, AccessFlags flags, int max_stack, int params,
ConstMethod::MethodType mt, TRAPS) {
address code_start = 0;
int code_length = 0;
InlineTableSizes sizes;
if (bytecodes != NULL && bytecodes->length() > 0) {
code_start = static_cast<address>(bytecodes->adr_at(0));
code_length = bytecodes->length();
}
Method* m = Method::allocate(cp->pool_holder()->class_loader_data(),
code_length, flags, &sizes,
mt, CHECK_NULL);
m->set_constants(NULL); // This will get filled in later
m->set_name_index(cp->utf8(name));
m->set_signature_index(cp->utf8(sig));
#ifdef CC_INTERP
ResultTypeFinder rtf(sig);
m->set_result_index(rtf.type());
#endif
m->set_size_of_parameters(params);
m->set_max_stack(max_stack);
m->set_max_locals(params);
m->constMethod()->set_stackmap_data(NULL);
m->set_code(code_start);
return m;
}
static void switchover_constant_pool(BytecodeConstantPool* bpool,
InstanceKlass* klass, GrowableArray<Method*>* new_methods, TRAPS) {
if (new_methods->length() > 0) {
ConstantPool* cp = bpool->create_constant_pool(CHECK);
if (cp != klass->constants()) {
klass->class_loader_data()->add_to_deallocate_list(klass->constants());
klass->set_constants(cp);
cp->set_pool_holder(klass);
for (int i = 0; i < new_methods->length(); ++i) {
new_methods->at(i)->set_constants(cp);
}
for (int i = 0; i < klass->methods()->length(); ++i) {
Method* mo = klass->methods()->at(i);
mo->set_constants(cp);
}
}
}
}
// Create default_methods list for the current class.
// With the VM only processing erased signatures, the VM only
// creates an overpass in a conflict case or a case with no candidates.
// This allows virtual methods to override the overpass, but ensures
// that a local method search will find the exception rather than an abstract
// or default method that is not a valid candidate.
static void create_defaults_and_exceptions(
GrowableArray<EmptyVtableSlot*>* slots,
InstanceKlass* klass, TRAPS) {
GrowableArray<Method*> overpasses;
GrowableArray<Method*> defaults;
BytecodeConstantPool bpool(klass->constants());
for (int i = 0; i < slots->length(); ++i) {
EmptyVtableSlot* slot = slots->at(i);
if (slot->is_bound()) {
MethodFamily* method = slot->get_binding();
BytecodeBuffer buffer;
#ifndef PRODUCT
if (TraceDefaultMethods) {
tty->print("for slot: ");
slot->print_on(tty);
tty->cr();
if (method->has_target()) {
method->print_selected(tty, 1);
} else if (method->throws_exception()) {
method->print_exception(tty, 1);
}
}
#endif // ndef PRODUCT
if (method->has_target()) {
Method* selected = method->get_selected_target();
if (selected->method_holder()->is_interface()) {
defaults.push(selected);
}
} else if (method->throws_exception()) {
int max_stack = assemble_method_error(&bpool, &buffer,
method->get_exception_name(), method->get_exception_message(), CHECK);
AccessFlags flags = accessFlags_from(
JVM_ACC_PUBLIC | JVM_ACC_SYNTHETIC | JVM_ACC_BRIDGE);
Method* m = new_method(&bpool, &buffer, slot->name(), slot->signature(),
flags, max_stack, slot->size_of_parameters(),
ConstMethod::OVERPASS, CHECK);
// We push to the methods list:
// overpass methods which are exception throwing methods
if (m != NULL) {
overpasses.push(m);
}
}
}
}
#ifndef PRODUCT
if (TraceDefaultMethods) {
tty->print_cr("Created %d overpass methods", overpasses.length());
tty->print_cr("Created %d default methods", defaults.length());
}
#endif // ndef PRODUCT
if (overpasses.length() > 0) {
switchover_constant_pool(&bpool, klass, &overpasses, CHECK);
merge_in_new_methods(klass, &overpasses, CHECK);
}
if (defaults.length() > 0) {
create_default_methods(klass, &defaults, CHECK);
}
}
static void create_default_methods( InstanceKlass* klass,
GrowableArray<Method*>* new_methods, TRAPS) {
int new_size = new_methods->length();
Array<Method*>* total_default_methods = MetadataFactory::new_array<Method*>(
klass->class_loader_data(), new_size, NULL, CHECK);
for (int index = 0; index < new_size; index++ ) {
total_default_methods->at_put(index, new_methods->at(index));
}
Method::sort_methods(total_default_methods, false, false);
klass->set_default_methods(total_default_methods);
}
static void sort_methods(GrowableArray<Method*>* methods) {
// Note that this must sort using the same key as is used for sorting
// methods in InstanceKlass.
bool sorted = true;
for (int i = methods->length() - 1; i > 0; --i) {
for (int j = 0; j < i; ++j) {
Method* m1 = methods->at(j);
Method* m2 = methods->at(j + 1);
if ((uintptr_t)m1->name() > (uintptr_t)m2->name()) {
methods->at_put(j, m2);
methods->at_put(j + 1, m1);
sorted = false;
}
}
if (sorted) break;
sorted = true;
}
#ifdef ASSERT
uintptr_t prev = 0;
for (int i = 0; i < methods->length(); ++i) {
Method* mh = methods->at(i);
uintptr_t nv = (uintptr_t)mh->name();
assert(nv >= prev, "Incorrect overpass method ordering");
prev = nv;
}
#endif
}
static void merge_in_new_methods(InstanceKlass* klass,
GrowableArray<Method*>* new_methods, TRAPS) {
enum { ANNOTATIONS, PARAMETERS, DEFAULTS, NUM_ARRAYS };
Array<Method*>* original_methods = klass->methods();
Array<int>* original_ordering = klass->method_ordering();
Array<int>* merged_ordering = Universe::the_empty_int_array();
int new_size = klass->methods()->length() + new_methods->length();
Array<Method*>* merged_methods = MetadataFactory::new_array<Method*>(
klass->class_loader_data(), new_size, NULL, CHECK);
// original_ordering might be empty if this class has no methods of its own
if (JvmtiExport::can_maintain_original_method_order() || DumpSharedSpaces) {
merged_ordering = MetadataFactory::new_array<int>(
klass->class_loader_data(), new_size, CHECK);
}
int method_order_index = klass->methods()->length();
sort_methods(new_methods);
// Perform grand merge of existing methods and new methods
int orig_idx = 0;
int new_idx = 0;
for (int i = 0; i < new_size; ++i) {
Method* orig_method = NULL;
Method* new_method = NULL;
if (orig_idx < original_methods->length()) {
orig_method = original_methods->at(orig_idx);
}
if (new_idx < new_methods->length()) {
new_method = new_methods->at(new_idx);
}
if (orig_method != NULL &&
(new_method == NULL || orig_method->name() < new_method->name())) {
merged_methods->at_put(i, orig_method);
original_methods->at_put(orig_idx, NULL);
if (merged_ordering->length() > 0) {
assert(original_ordering != NULL && original_ordering->length() > 0,
"should have original order information for this method");
merged_ordering->at_put(i, original_ordering->at(orig_idx));
}
++orig_idx;
} else {
merged_methods->at_put(i, new_method);
if (merged_ordering->length() > 0) {
merged_ordering->at_put(i, method_order_index++);
}
++new_idx;
}
// update idnum for new location
merged_methods->at(i)->set_method_idnum(i);
}
// Verify correct order
#ifdef ASSERT
uintptr_t prev = 0;
for (int i = 0; i < merged_methods->length(); ++i) {
Method* mo = merged_methods->at(i);
uintptr_t nv = (uintptr_t)mo->name();
assert(nv >= prev, "Incorrect method ordering");
prev = nv;
}
#endif
// Replace klass methods with new merged lists
klass->set_methods(merged_methods);
klass->set_initial_method_idnum(new_size);
klass->set_method_ordering(merged_ordering);
// Free metadata
ClassLoaderData* cld = klass->class_loader_data();
if (original_methods->length() > 0) {
MetadataFactory::free_array(cld, original_methods);
}
if (original_ordering != NULL && original_ordering->length() > 0) {
MetadataFactory::free_array(cld, original_ordering);
}
}