// Revised lookup semantics introduced 1.3 (Kestral beta)
void klassVtable::initialize_vtable(bool checkconstraints, TRAPS) {
// Note: Arrays can have intermediate array supers. Use java_super to skip them.
KlassHandle super (THREAD, klass()->java_super());
int nofNewEntries = 0;
if (PrintVtables && !klass()->oop_is_array()) {
ResourceMark rm(THREAD);
tty->print_cr("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()) {
// just clear everything
for (int i = 0; i < _length; i++) table()[i].clear();
return;
}
int super_vtable_len = initialize_from_super(super);
if (klass()->oop_is_array()) {
assert(super_vtable_len == _length, "arrays shouldn't introduce new methods");
} else {
assert(_klass->oop_is_instance(), "must be instanceKlass");
objArrayHandle methods(THREAD, ik()->methods());
int len = methods()->length();
int initialized = super_vtable_len;
// update_inherited_vtable can stop for gc - ensure using handles
for (int i = 0; i < len; i++) {
HandleMark hm(THREAD);
assert(methods()->obj_at(i)->is_method(), "must be a methodOop");
methodHandle mh(THREAD, (methodOop)methods()->obj_at(i));
bool needs_new_entry = update_inherited_vtable(ik(), mh, super_vtable_len, checkconstraints, CHECK);
if (needs_new_entry) {
put_method_at(mh(), initialized);
mh()->set_vtable_index(initialized); // set primary vtable index
initialized++;
}
}
// add miranda methods; it will also update the value of initialized
fill_in_mirandas(initialized);
// In class hierarchies where the accessibility is not increasing (i.e., going from private ->
// package_private -> publicprotected), the vtable might actually be smaller than our initial
// calculation.
assert(initialized <= _length, "vtable initialization failed");
for(;initialized < _length; initialized++) {
put_method_at(NULL, initialized);
}
NOT_PRODUCT(verify(tty, true));
}
}
// 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, methodHandle target_method, int super_vtable_len,
bool checkconstraints, TRAPS) {
ResourceMark rm;
bool allocate_new = true;
assert(klass->oop_is_instance(), "must be instanceKlass");
// 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(methodOopDesc::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 (klass->is_final() || target_method()->is_final()) {
// 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;
}
// we need a new entry if there is no superclass
if (klass->super() == NULL) {
return allocate_new;
}
// private methods always have a new entry in the vtable
// specification interpretation since classic has
// private methods not overriding
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();
Handle target_loader(THREAD, _klass->class_loader());
Symbol* target_classname = _klass->name();
for(int i = 0; i < super_vtable_len; i++) {
methodOop super_method = method_at(i);
// Check if method name matches
if (super_method->name() == name && super_method->signature() == signature) {
// get super_klass for method_holder for the found method
instanceKlass* super_klass = instanceKlass::cast(super_method->method_holder());
if ((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))) {
// overriding, so no new entry
allocate_new = false;
if (checkconstraints) {
// 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 (target_loader() != super_loader()) {
ResourceMark rm(THREAD);
char* failed_type_name =
SystemDictionary::check_signature_loaders(signature, target_loader,
super_loader, true,
CHECK_(false));
if (failed_type_name != NULL) {
const char* msg = "loader constraint violation: when resolving "
"overridden method \"%s\" the class loader (instance"
" of %s) of the current class, %s, and its superclass loader "
"(instance of %s), have different Class objects for the type "
"%s used in the signature";
char* sig = target_method()->name_and_sig_as_C_string();
const char* loader1 = SystemDictionary::loader_name(target_loader());
char* current = _klass->name()->as_C_string();
const char* loader2 = SystemDictionary::loader_name(super_loader());
size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
strlen(current) + strlen(loader2) + strlen(failed_type_name);
char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
failed_type_name);
THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
}
}
}
put_method_at(target_method(), i);
target_method()->set_vtable_index(i);
#ifndef PRODUCT
if (PrintVtables && Verbose) {
tty->print("overriding with %s::%s index %d, original flags: ",
_klass->internal_name(), (target_method() != NULL) ?
target_method()->name()->as_C_string() : "<NULL>", i);
super_method->access_flags().print_on(tty);
tty->print("overriders flags: ");
target_method->access_flags().print_on(tty);
tty->cr();
}
#endif /*PRODUCT*/
} else {
// 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_super_vtable(instanceKlass* klass, methodHandle target_method, int super_vtable_len, bool checkconstraints, TRAPS) {
ResourceMark rm;
bool allocate_new = true;
assert(klass->oop_is_instance(), "must be instanceKlass");
// 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(methodOopDesc::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 (klass->is_final() || target_method()->is_final()) {
// 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;
}
// we need a new entry if there is no superclass
if (klass->super() == NULL) {
return allocate_new;
}
// private methods always have a new entry in the vtable
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, not
// unhandled oops unless they are reinitialized for each loop
// handles for name, signature, klass, target_method
// not for match_method, holder
symbolHandle name(THREAD,target_method()->name());
symbolHandle signature(THREAD,target_method()->signature());
for(int i = 0; i < super_vtable_len; i++) {
methodOop match_method = method_at(i);
// Check if method name matches
if (match_method->name() == name() && match_method->signature() == signature()) {
instanceKlass* holder = (THREAD, instanceKlass::cast(match_method->method_holder()));
// Check if the match_method is accessable from current class
bool same_package_init = false;
bool same_package_flag = false;
bool simple_match = match_method->is_public() || match_method->is_protected();
if (!simple_match) {
same_package_init = true;
same_package_flag = holder->is_same_class_package(_klass->class_loader(), _klass->name());
simple_match = match_method->is_package_private() && same_package_flag;
}
// match_method is the superclass' method. Note we can't override
// and shouldn't access superclass' ACC_PRIVATE methods
// (although they have been copied into our vtable)
// A simple form of this statement is:
// if ( (match_method->is_public() || match_method->is_protected()) ||
// (match_method->is_package_private() && holder->is_same_class_package(klass->class_loader(), klass->name()))) {
//
// The complexity is introduced it avoid recomputing 'is_same_class_package' which is expensive.
if (simple_match) {
// Check if target_method and match_method has same level of accessibility. The accesibility of the
// match method is the "most-general" visibility of all entries at it's particular vtable index for
// all superclasses. This check must be done before we override the current entry in the vtable.
AccessType at = vtable_accessibility_at(i);
bool same_access = false;
if ( (at == acc_publicprotected && (target_method()->is_public() || target_method()->is_protected()))
|| (at == acc_package_private && (target_method()->is_package_private() &&
(( same_package_init && same_package_flag) ||
(!same_package_init&&holder->is_same_class_package(_klass->class_loader(),_klass->name())))))){
same_access = true;
}
if (checkconstraints) {
// 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.
symbolHandle signature(THREAD, target_method()->signature());
Handle this_loader(THREAD, _klass->class_loader());
instanceKlassHandle super_klass(THREAD, _klass->super());
Handle super_loader(THREAD, super_klass->class_loader());
if (this_loader() != super_loader()) {
ResourceMark rm(THREAD);
char* failed_type_name =
SystemDictionary::check_signature_loaders(signature, this_loader,
super_loader, true,
CHECK_(false));
if (failed_type_name != NULL) {
const char* msg = "loader constraint violation: when resolving "
"overridden method \"%s\" the class loader (instance"
" of %s) of the current class, %s, and its superclass loader "
"(instance of %s), have different Class objects for the type "
"%s used in the signature";
char* sig = target_method()->name_and_sig_as_C_string();
const char* loader1 = SystemDictionary::loader_name(this_loader());
char* current = _klass->name()->as_C_string();
const char* loader2 = SystemDictionary::loader_name(super_loader());
size_t buflen = strlen(msg) + strlen(sig) + strlen(loader1) +
strlen(current) + strlen(loader2) + strlen(failed_type_name);
char* buf = NEW_RESOURCE_ARRAY_IN_THREAD(THREAD, char, buflen);
jio_snprintf(buf, buflen, msg, sig, loader1, current, loader2,
failed_type_name);
THROW_MSG_(vmSymbols::java_lang_LinkageError(), buf, false);
}
}
}
put_method_at(target_method(), i);
if (same_access) {
// target and match has same accessiblity - share entry
allocate_new = false;
target_method()->set_vtable_index(i);
#ifndef PRODUCT
if (PrintVtables && Verbose) {
AccessType targetacc;
if (target_method()->is_protected() ||
target_method()->is_public()) {
targetacc = acc_publicprotected;
} else {
targetacc = target_method()->is_package_private() ? acc_package_private : acc_private;
}
tty->print_cr("overriding with %s::%s index %d, original flags: %x overriders flags: %x",
_klass->internal_name(), (target_method() != NULL) ?
target_method()->name()->as_C_string() : "<NULL>", i,
at, targetacc);
}
#endif /*PRODUCT*/
} else {
#ifndef PRODUCT
if (PrintVtables && Verbose) {
AccessType targetacc;
if (target_method()->is_protected() ||
target_method()->is_public()) {
targetacc = acc_publicprotected;
} else {
targetacc = target_method()->is_package_private() ? acc_package_private : acc_private;
}
tty->print_cr("override %s %s::%s at index %d, original flags: %x overriders flags: %x",
allocate_new ? "+ new" : "only",
_klass->internal_name(), (target_method() != NULL) ?
target_method()->name()->as_C_string() : "<NULL>", i,
at, targetacc);
}
#endif /*PRODUCT*/
}
}
}