1/*
2 * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25#include "precompiled.hpp"
26#include "classfile/systemDictionary.hpp"
27#include "classfile/vmSymbols.hpp"
28#include "code/nmethod.hpp"
29#include "compiler/compileBroker.hpp"
30#include "interpreter/interpreter.hpp"
31#include "interpreter/linkResolver.hpp"
32#include "memory/universe.hpp"
33#include "oops/method.inline.hpp"
34#include "oops/oop.inline.hpp"
35#include "prims/jniCheck.hpp"
36#include "runtime/compilationPolicy.hpp"
37#include "runtime/handles.inline.hpp"
38#include "runtime/interfaceSupport.inline.hpp"
39#include "runtime/javaCalls.hpp"
40#include "runtime/jniHandles.inline.hpp"
41#include "runtime/mutexLocker.hpp"
42#include "runtime/os.inline.hpp"
43#include "runtime/sharedRuntime.hpp"
44#include "runtime/signature.hpp"
45#include "runtime/stubRoutines.hpp"
46#include "runtime/thread.inline.hpp"
47
48// -----------------------------------------------------
49// Implementation of JavaCallWrapper
50
51JavaCallWrapper::JavaCallWrapper(const methodHandle& callee_method, Handle receiver, JavaValue* result, TRAPS) {
52 JavaThread* thread = (JavaThread *)THREAD;
53 bool clear_pending_exception = true;
54
55 guarantee(thread->is_Java_thread(), "crucial check - the VM thread cannot and must not escape to Java code");
56 assert(!thread->owns_locks(), "must release all locks when leaving VM");
57 guarantee(thread->can_call_java(), "cannot make java calls from the native compiler");
58 _result = result;
59
60 // Allocate handle block for Java code. This must be done before we change thread_state to _thread_in_Java_or_stub,
61 // since it can potentially block.
62 JNIHandleBlock* new_handles = JNIHandleBlock::allocate_block(thread);
63
64 // After this, we are official in JavaCode. This needs to be done before we change any of the thread local
65 // info, since we cannot find oops before the new information is set up completely.
66 ThreadStateTransition::transition(thread, _thread_in_vm, _thread_in_Java);
67
68 // Make sure that we handle asynchronous stops and suspends _before_ we clear all thread state
69 // in JavaCallWrapper::JavaCallWrapper(). This way, we can decide if we need to do any pd actions
70 // to prepare for stop/suspend (flush register windows on sparcs, cache sp, or other state).
71 if (thread->has_special_runtime_exit_condition()) {
72 thread->handle_special_runtime_exit_condition();
73 if (HAS_PENDING_EXCEPTION) {
74 clear_pending_exception = false;
75 }
76 }
77
78
79 // Make sure to set the oop's after the thread transition - since we can block there. No one is GC'ing
80 // the JavaCallWrapper before the entry frame is on the stack.
81 _callee_method = callee_method();
82 _receiver = receiver();
83
84#ifdef CHECK_UNHANDLED_OOPS
85 THREAD->allow_unhandled_oop(&_receiver);
86#endif // CHECK_UNHANDLED_OOPS
87
88 _thread = (JavaThread *)thread;
89 _handles = _thread->active_handles(); // save previous handle block & Java frame linkage
90
91 // For the profiler, the last_Java_frame information in thread must always be in
92 // legal state. We have no last Java frame if last_Java_sp == NULL so
93 // the valid transition is to clear _last_Java_sp and then reset the rest of
94 // the (platform specific) state.
95
96 _anchor.copy(_thread->frame_anchor());
97 _thread->frame_anchor()->clear();
98
99 debug_only(_thread->inc_java_call_counter());
100 _thread->set_active_handles(new_handles); // install new handle block and reset Java frame linkage
101
102 assert (_thread->thread_state() != _thread_in_native, "cannot set native pc to NULL");
103
104 // clear any pending exception in thread (native calls start with no exception pending)
105 if(clear_pending_exception) {
106 _thread->clear_pending_exception();
107 }
108
109 if (_anchor.last_Java_sp() == NULL) {
110 _thread->record_base_of_stack_pointer();
111 }
112}
113
114
115JavaCallWrapper::~JavaCallWrapper() {
116 assert(_thread == JavaThread::current(), "must still be the same thread");
117
118 // restore previous handle block & Java frame linkage
119 JNIHandleBlock *_old_handles = _thread->active_handles();
120 _thread->set_active_handles(_handles);
121
122 _thread->frame_anchor()->zap();
123
124 debug_only(_thread->dec_java_call_counter());
125
126 if (_anchor.last_Java_sp() == NULL) {
127 _thread->set_base_of_stack_pointer(NULL);
128 }
129
130
131 // Old thread-local info. has been restored. We are not back in the VM.
132 ThreadStateTransition::transition_from_java(_thread, _thread_in_vm);
133
134 // State has been restored now make the anchor frame visible for the profiler.
135 // Do this after the transition because this allows us to put an assert
136 // the Java->vm transition which checks to see that stack is not walkable
137 // on sparc/ia64 which will catch violations of the reseting of last_Java_frame
138 // invariants (i.e. _flags always cleared on return to Java)
139
140 _thread->frame_anchor()->copy(&_anchor);
141
142 // Release handles after we are marked as being inside the VM again, since this
143 // operation might block
144 JNIHandleBlock::release_block(_old_handles, _thread);
145}
146
147
148void JavaCallWrapper::oops_do(OopClosure* f) {
149 f->do_oop((oop*)&_receiver);
150 handles()->oops_do(f);
151}
152
153
154// Helper methods
155static BasicType runtime_type_from(JavaValue* result) {
156 switch (result->get_type()) {
157 case T_BOOLEAN: // fall through
158 case T_CHAR : // fall through
159 case T_SHORT : // fall through
160 case T_INT : // fall through
161#ifndef _LP64
162 case T_OBJECT : // fall through
163 case T_ARRAY : // fall through
164#endif
165 case T_BYTE : // fall through
166 case T_VOID : return T_INT;
167 case T_LONG : return T_LONG;
168 case T_FLOAT : return T_FLOAT;
169 case T_DOUBLE : return T_DOUBLE;
170#ifdef _LP64
171 case T_ARRAY : // fall through
172 case T_OBJECT: return T_OBJECT;
173#endif
174 default:
175 ShouldNotReachHere();
176 return T_ILLEGAL;
177 }
178}
179
180// ============ Virtual calls ============
181
182void JavaCalls::call_virtual(JavaValue* result, Klass* spec_klass, Symbol* name, Symbol* signature, JavaCallArguments* args, TRAPS) {
183 CallInfo callinfo;
184 Handle receiver = args->receiver();
185 Klass* recvrKlass = receiver.is_null() ? (Klass*)NULL : receiver->klass();
186 LinkInfo link_info(spec_klass, name, signature);
187 LinkResolver::resolve_virtual_call(
188 callinfo, receiver, recvrKlass, link_info, true, CHECK);
189 methodHandle method = callinfo.selected_method();
190 assert(method.not_null(), "should have thrown exception");
191
192 // Invoke the method
193 JavaCalls::call(result, method, args, CHECK);
194}
195
196
197void JavaCalls::call_virtual(JavaValue* result, Handle receiver, Klass* spec_klass, Symbol* name, Symbol* signature, TRAPS) {
198 JavaCallArguments args(receiver);
199 call_virtual(result, spec_klass, name, signature, &args, CHECK);
200}
201
202
203void JavaCalls::call_virtual(JavaValue* result, Handle receiver, Klass* spec_klass, Symbol* name, Symbol* signature, Handle arg1, TRAPS) {
204 JavaCallArguments args(receiver);
205 args.push_oop(arg1);
206 call_virtual(result, spec_klass, name, signature, &args, CHECK);
207}
208
209
210
211void JavaCalls::call_virtual(JavaValue* result, Handle receiver, Klass* spec_klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, TRAPS) {
212 JavaCallArguments args(receiver);
213 args.push_oop(arg1);
214 args.push_oop(arg2);
215 call_virtual(result, spec_klass, name, signature, &args, CHECK);
216}
217
218
219// ============ Special calls ============
220
221void JavaCalls::call_special(JavaValue* result, Klass* klass, Symbol* name, Symbol* signature, JavaCallArguments* args, TRAPS) {
222 CallInfo callinfo;
223 LinkInfo link_info(klass, name, signature);
224 LinkResolver::resolve_special_call(callinfo, args->receiver(), link_info, CHECK);
225 methodHandle method = callinfo.selected_method();
226 assert(method.not_null(), "should have thrown exception");
227
228 // Invoke the method
229 JavaCalls::call(result, method, args, CHECK);
230}
231
232
233void JavaCalls::call_special(JavaValue* result, Handle receiver, Klass* klass, Symbol* name, Symbol* signature, TRAPS) {
234 JavaCallArguments args(receiver);
235 call_special(result, klass, name, signature, &args, CHECK);
236}
237
238
239void JavaCalls::call_special(JavaValue* result, Handle receiver, Klass* klass, Symbol* name, Symbol* signature, Handle arg1, TRAPS) {
240 JavaCallArguments args(receiver);
241 args.push_oop(arg1);
242 call_special(result, klass, name, signature, &args, CHECK);
243}
244
245
246void JavaCalls::call_special(JavaValue* result, Handle receiver, Klass* klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, TRAPS) {
247 JavaCallArguments args(receiver);
248 args.push_oop(arg1);
249 args.push_oop(arg2);
250 call_special(result, klass, name, signature, &args, CHECK);
251}
252
253
254// ============ Static calls ============
255
256void JavaCalls::call_static(JavaValue* result, Klass* klass, Symbol* name, Symbol* signature, JavaCallArguments* args, TRAPS) {
257 CallInfo callinfo;
258 LinkInfo link_info(klass, name, signature);
259 LinkResolver::resolve_static_call(callinfo, link_info, true, CHECK);
260 methodHandle method = callinfo.selected_method();
261 assert(method.not_null(), "should have thrown exception");
262
263 // Invoke the method
264 JavaCalls::call(result, method, args, CHECK);
265}
266
267
268void JavaCalls::call_static(JavaValue* result, Klass* klass, Symbol* name, Symbol* signature, TRAPS) {
269 JavaCallArguments args;
270 call_static(result, klass, name, signature, &args, CHECK);
271}
272
273
274void JavaCalls::call_static(JavaValue* result, Klass* klass, Symbol* name, Symbol* signature, Handle arg1, TRAPS) {
275 JavaCallArguments args(arg1);
276 call_static(result, klass, name, signature, &args, CHECK);
277}
278
279
280void JavaCalls::call_static(JavaValue* result, Klass* klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, TRAPS) {
281 JavaCallArguments args;
282 args.push_oop(arg1);
283 args.push_oop(arg2);
284 call_static(result, klass, name, signature, &args, CHECK);
285}
286
287
288void JavaCalls::call_static(JavaValue* result, Klass* klass, Symbol* name, Symbol* signature, Handle arg1, Handle arg2, Handle arg3, TRAPS) {
289 JavaCallArguments args;
290 args.push_oop(arg1);
291 args.push_oop(arg2);
292 args.push_oop(arg3);
293 call_static(result, klass, name, signature, &args, CHECK);
294}
295
296// ============ allocate and initialize new object instance ============
297
298Handle JavaCalls::construct_new_instance(InstanceKlass* klass, Symbol* constructor_signature, JavaCallArguments* args, TRAPS) {
299 klass->initialize(CHECK_NH); // Quick no-op if already initialized.
300 Handle obj = klass->allocate_instance_handle(CHECK_NH);
301 JavaValue void_result(T_VOID);
302 args->set_receiver(obj); // inserts <obj> as the first argument.
303 JavaCalls::call_special(&void_result, klass,
304 vmSymbols::object_initializer_name(),
305 constructor_signature, args, CHECK_NH);
306 // Already returned a Null Handle if any exception is pending.
307 return obj;
308}
309
310Handle JavaCalls::construct_new_instance(InstanceKlass* klass, Symbol* constructor_signature, TRAPS) {
311 JavaCallArguments args;
312 return JavaCalls::construct_new_instance(klass, constructor_signature, &args, THREAD);
313}
314
315Handle JavaCalls::construct_new_instance(InstanceKlass* klass, Symbol* constructor_signature, Handle arg1, TRAPS) {
316 JavaCallArguments args;
317 args.push_oop(arg1);
318 return JavaCalls::construct_new_instance(klass, constructor_signature, &args, THREAD);
319}
320
321Handle JavaCalls::construct_new_instance(InstanceKlass* klass, Symbol* constructor_signature, Handle arg1, Handle arg2, TRAPS) {
322 JavaCallArguments args;
323 args.push_oop(arg1);
324 args.push_oop(arg2);
325 return JavaCalls::construct_new_instance(klass, constructor_signature, &args, THREAD);
326}
327
328// -------------------------------------------------
329// Implementation of JavaCalls (low level)
330
331
332void JavaCalls::call(JavaValue* result, const methodHandle& method, JavaCallArguments* args, TRAPS) {
333 // Check if we need to wrap a potential OS exception handler around thread
334 // This is used for e.g. Win32 structured exception handlers
335 assert(THREAD->is_Java_thread(), "only JavaThreads can make JavaCalls");
336 // Need to wrap each and every time, since there might be native code down the
337 // stack that has installed its own exception handlers
338 os::os_exception_wrapper(call_helper, result, method, args, THREAD);
339}
340
341void JavaCalls::call_helper(JavaValue* result, const methodHandle& method, JavaCallArguments* args, TRAPS) {
342
343 JavaThread* thread = (JavaThread*)THREAD;
344 assert(thread->is_Java_thread(), "must be called by a java thread");
345 assert(method.not_null(), "must have a method to call");
346 assert(!SafepointSynchronize::is_at_safepoint(), "call to Java code during VM operation");
347 assert(!thread->handle_area()->no_handle_mark_active(), "cannot call out to Java here");
348
349
350 CHECK_UNHANDLED_OOPS_ONLY(thread->clear_unhandled_oops();)
351
352#if INCLUDE_JVMCI
353 // Gets the nmethod (if any) that should be called instead of normal target
354 nmethod* alternative_target = args->alternative_target();
355 if (alternative_target == NULL) {
356#endif
357// Verify the arguments
358
359 if (CheckJNICalls) {
360 args->verify(method, result->get_type());
361 }
362 else debug_only(args->verify(method, result->get_type()));
363#if INCLUDE_JVMCI
364 }
365#else
366
367 // Ignore call if method is empty
368 if (method->is_empty_method()) {
369 assert(result->get_type() == T_VOID, "an empty method must return a void value");
370 return;
371 }
372#endif
373
374#ifdef ASSERT
375 { InstanceKlass* holder = method->method_holder();
376 // A klass might not be initialized since JavaCall's might be used during the executing of
377 // the <clinit>. For example, a Thread.start might start executing on an object that is
378 // not fully initialized! (bad Java programming style)
379 assert(holder->is_linked(), "rewriting must have taken place");
380 }
381#endif
382
383 CompilationPolicy::compile_if_required(method, CHECK);
384
385 // Since the call stub sets up like the interpreter we call the from_interpreted_entry
386 // so we can go compiled via a i2c. Otherwise initial entry method will always
387 // run interpreted.
388 address entry_point = method->from_interpreted_entry();
389 if (JvmtiExport::can_post_interpreter_events() && thread->is_interp_only_mode()) {
390 entry_point = method->interpreter_entry();
391 }
392
393 // Figure out if the result value is an oop or not (Note: This is a different value
394 // than result_type. result_type will be T_INT of oops. (it is about size)
395 BasicType result_type = runtime_type_from(result);
396 bool oop_result_flag = (result->get_type() == T_OBJECT || result->get_type() == T_ARRAY);
397
398 // NOTE: if we move the computation of the result_val_address inside
399 // the call to call_stub, the optimizer produces wrong code.
400 intptr_t* result_val_address = (intptr_t*)(result->get_value_addr());
401
402 // Find receiver
403 Handle receiver = (!method->is_static()) ? args->receiver() : Handle();
404
405 // When we reenter Java, we need to reenable the reserved/yellow zone which
406 // might already be disabled when we are in VM.
407 if (!thread->stack_guards_enabled()) {
408 thread->reguard_stack();
409 }
410
411 // Check that there are shadow pages available before changing thread state
412 // to Java. Calculate current_stack_pointer here to make sure
413 // stack_shadow_pages_available() and bang_stack_shadow_pages() use the same sp.
414 address sp = os::current_stack_pointer();
415 if (!os::stack_shadow_pages_available(THREAD, method, sp)) {
416 // Throw stack overflow exception with preinitialized exception.
417 Exceptions::throw_stack_overflow_exception(THREAD, __FILE__, __LINE__, method);
418 return;
419 } else {
420 // Touch pages checked if the OS needs them to be touched to be mapped.
421 os::map_stack_shadow_pages(sp);
422 }
423
424#if INCLUDE_JVMCI
425 if (alternative_target != NULL) {
426 if (alternative_target->is_alive() && !alternative_target->is_unloading()) {
427 thread->set_jvmci_alternate_call_target(alternative_target->verified_entry_point());
428 entry_point = method->adapter()->get_i2c_entry();
429 } else {
430 THROW(vmSymbols::jdk_vm_ci_code_InvalidInstalledCodeException());
431 }
432 }
433#endif
434
435 // do call
436 { JavaCallWrapper link(method, receiver, result, CHECK);
437 { HandleMark hm(thread); // HandleMark used by HandleMarkCleaner
438
439 StubRoutines::call_stub()(
440 (address)&link,
441 // (intptr_t*)&(result->_value), // see NOTE above (compiler problem)
442 result_val_address, // see NOTE above (compiler problem)
443 result_type,
444 method(),
445 entry_point,
446 args->parameters(),
447 args->size_of_parameters(),
448 CHECK
449 );
450
451 result = link.result(); // circumvent MS C++ 5.0 compiler bug (result is clobbered across call)
452 // Preserve oop return value across possible gc points
453 if (oop_result_flag) {
454 thread->set_vm_result((oop) result->get_jobject());
455 }
456 }
457 } // Exit JavaCallWrapper (can block - potential return oop must be preserved)
458
459 // Check if a thread stop or suspend should be executed
460 // The following assert was not realistic. Thread.stop can set that bit at any moment.
461 //assert(!thread->has_special_runtime_exit_condition(), "no async. exceptions should be installed");
462
463 // Restore possible oop return
464 if (oop_result_flag) {
465 result->set_jobject((jobject)thread->vm_result());
466 thread->set_vm_result(NULL);
467 }
468}
469
470
471//--------------------------------------------------------------------------------------
472// Implementation of JavaCallArguments
473
474inline bool is_value_state_indirect_oop(uint state) {
475 assert(state != JavaCallArguments::value_state_oop,
476 "Checking for handles after removal");
477 assert(state < JavaCallArguments::value_state_limit,
478 "Invalid value state %u", state);
479 return state != JavaCallArguments::value_state_primitive;
480}
481
482inline oop resolve_indirect_oop(intptr_t value, uint state) {
483 switch (state) {
484 case JavaCallArguments::value_state_handle:
485 {
486 oop* ptr = reinterpret_cast<oop*>(value);
487 return Handle::raw_resolve(ptr);
488 }
489
490 case JavaCallArguments::value_state_jobject:
491 {
492 jobject obj = reinterpret_cast<jobject>(value);
493 return JNIHandles::resolve(obj);
494 }
495
496 default:
497 ShouldNotReachHere();
498 return NULL;
499 }
500}
501
502intptr_t* JavaCallArguments::parameters() {
503 // First convert all handles to oops
504 for(int i = 0; i < _size; i++) {
505 uint state = _value_state[i];
506 assert(state != value_state_oop, "Multiple handle conversions");
507 if (is_value_state_indirect_oop(state)) {
508 oop obj = resolve_indirect_oop(_value[i], state);
509 _value[i] = cast_from_oop<intptr_t>(obj);
510 _value_state[i] = value_state_oop;
511 }
512 }
513 // Return argument vector
514 return _value;
515}
516
517
518class SignatureChekker : public SignatureIterator {
519 private:
520 int _pos;
521 BasicType _return_type;
522 u_char* _value_state;
523 intptr_t* _value;
524
525 public:
526 bool _is_return;
527
528 SignatureChekker(Symbol* signature,
529 BasicType return_type,
530 bool is_static,
531 u_char* value_state,
532 intptr_t* value) :
533 SignatureIterator(signature),
534 _pos(0),
535 _return_type(return_type),
536 _value_state(value_state),
537 _value(value),
538 _is_return(false)
539 {
540 if (!is_static) {
541 check_value(true); // Receiver must be an oop
542 }
543 }
544
545 void check_value(bool type) {
546 uint state = _value_state[_pos++];
547 if (type) {
548 guarantee(is_value_state_indirect_oop(state),
549 "signature does not match pushed arguments: %u at %d",
550 state, _pos - 1);
551 } else {
552 guarantee(state == JavaCallArguments::value_state_primitive,
553 "signature does not match pushed arguments: %u at %d",
554 state, _pos - 1);
555 }
556 }
557
558 void check_doing_return(bool state) { _is_return = state; }
559
560 void check_return_type(BasicType t) {
561 guarantee(_is_return && t == _return_type, "return type does not match");
562 }
563
564 void check_int(BasicType t) {
565 if (_is_return) {
566 check_return_type(t);
567 return;
568 }
569 check_value(false);
570 }
571
572 void check_double(BasicType t) { check_long(t); }
573
574 void check_long(BasicType t) {
575 if (_is_return) {
576 check_return_type(t);
577 return;
578 }
579
580 check_value(false);
581 check_value(false);
582 }
583
584 void check_obj(BasicType t) {
585 if (_is_return) {
586 check_return_type(t);
587 return;
588 }
589
590 intptr_t v = _value[_pos];
591 if (v != 0) {
592 // v is a "handle" referring to an oop, cast to integral type.
593 // There shouldn't be any handles in very low memory.
594 guarantee((size_t)v >= (size_t)os::vm_page_size(),
595 "Bad JNI oop argument %d: " PTR_FORMAT, _pos, v);
596 // Verify the pointee.
597 oop vv = resolve_indirect_oop(v, _value_state[_pos]);
598 guarantee(oopDesc::is_oop_or_null(vv, true),
599 "Bad JNI oop argument %d: " PTR_FORMAT " -> " PTR_FORMAT,
600 _pos, v, p2i(vv));
601 }
602
603 check_value(true); // Verify value state.
604 }
605
606 void do_bool() { check_int(T_BOOLEAN); }
607 void do_char() { check_int(T_CHAR); }
608 void do_float() { check_int(T_FLOAT); }
609 void do_double() { check_double(T_DOUBLE); }
610 void do_byte() { check_int(T_BYTE); }
611 void do_short() { check_int(T_SHORT); }
612 void do_int() { check_int(T_INT); }
613 void do_long() { check_long(T_LONG); }
614 void do_void() { check_return_type(T_VOID); }
615 void do_object(int begin, int end) { check_obj(T_OBJECT); }
616 void do_array(int begin, int end) { check_obj(T_OBJECT); }
617};
618
619
620void JavaCallArguments::verify(const methodHandle& method, BasicType return_type) {
621 guarantee(method->size_of_parameters() == size_of_parameters(), "wrong no. of arguments pushed");
622
623 // Treat T_OBJECT and T_ARRAY as the same
624 if (return_type == T_ARRAY) return_type = T_OBJECT;
625
626 // Check that oop information is correct
627 Symbol* signature = method->signature();
628
629 SignatureChekker sc(signature,
630 return_type,
631 method->is_static(),
632 _value_state,
633 _value);
634 sc.iterate_parameters();
635 sc.check_doing_return(true);
636 sc.iterate_returntype();
637}
638