1 /* 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. Oracle designates this 7 * particular file as subject to the "Classpath" exception as provided 8 * by Oracle in the LICENSE file that accompanied this code. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 */ 24 25 /* 26 * This file is available under and governed by the GNU General Public 27 * License version 2 only, as published by the Free Software Foundation. 28 * However, the following notice accompanied the original version of this 29 * file: 30 * 31 * ASM: a very small and fast Java bytecode manipulation framework 32 * Copyright (c) 2000-2011 INRIA, France Telecom 33 * All rights reserved. 34 * 35 * Redistribution and use in source and binary forms, with or without 36 * modification, are permitted provided that the following conditions 37 * are met: 38 * 1. Redistributions of source code must retain the above copyright 39 * notice, this list of conditions and the following disclaimer. 40 * 2. Redistributions in binary form must reproduce the above copyright 41 * notice, this list of conditions and the following disclaimer in the 42 * documentation and/or other materials provided with the distribution. 43 * 3. Neither the name of the copyright holders nor the names of its 44 * contributors may be used to endorse or promote products derived from 45 * this software without specific prior written permission. 46 * 47 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 48 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 49 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 50 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 51 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 52 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 53 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 54 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 55 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 56 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 57 * THE POSSIBILITY OF SUCH DAMAGE. 58 */ 59 package jdk.internal.org.objectweb.asm.tree.analysis; 60 61 import java.util.ArrayList; 62 import java.util.List; 63 64 import jdk.internal.org.objectweb.asm.Opcodes; 65 import jdk.internal.org.objectweb.asm.Type; 66 import jdk.internal.org.objectweb.asm.tree.AbstractInsnNode; 67 import jdk.internal.org.objectweb.asm.tree.IincInsnNode; 68 import jdk.internal.org.objectweb.asm.tree.InvokeDynamicInsnNode; 69 import jdk.internal.org.objectweb.asm.tree.MethodInsnNode; 70 import jdk.internal.org.objectweb.asm.tree.MultiANewArrayInsnNode; 71 import jdk.internal.org.objectweb.asm.tree.VarInsnNode; 72 73 /** 74 * A symbolic execution stack frame. A stack frame contains a set of local 75 * variable slots, and an operand stack. Warning: long and double values are 76 * represented by <i>two</i> slots in local variables, and by <i>one</i> slot in 77 * the operand stack. 78 * 79 * @param <V> 80 * type of the Value used for the analysis. 81 * 82 * @author Eric Bruneton 83 */ 84 public class Frame<V extends Value> { 85 86 /** 87 * The expected return type of the analyzed method, or <tt>null</tt> if the 88 * method returns void. 89 */ 90 private V returnValue; 91 92 /** 93 * The local variables and operand stack of this frame. 94 */ 95 private V[] values; 96 97 /** 98 * The number of local variables of this frame. 99 */ 100 private int locals; 101 102 /** 103 * The number of elements in the operand stack. 104 */ 105 private int top; 106 107 /** 108 * Constructs a new frame with the given size. 109 * 110 * @param nLocals 111 * the maximum number of local variables of the frame. 112 * @param nStack 113 * the maximum stack size of the frame. 114 */ 115 public Frame(final int nLocals, final int nStack) { 116 this.values = (V[]) new Value[nLocals + nStack]; 117 this.locals = nLocals; 118 } 119 120 /** 121 * Constructs a new frame that is identical to the given frame. 122 * 123 * @param src 124 * a frame. 125 */ 126 public Frame(final Frame<? extends V> src) { 127 this(src.locals, src.values.length - src.locals); 128 init(src); 129 } 130 131 /** 132 * Copies the state of the given frame into this frame. 133 * 134 * @param src 135 * a frame. 136 * @return this frame. 137 */ 138 public Frame<V> init(final Frame<? extends V> src) { 139 returnValue = src.returnValue; 140 System.arraycopy(src.values, 0, values, 0, values.length); 141 top = src.top; 142 return this; 143 } 144 145 /** 146 * Sets the expected return type of the analyzed method. 147 * 148 * @param v 149 * the expected return type of the analyzed method, or 150 * <tt>null</tt> if the method returns void. 151 */ 152 public void setReturn(final V v) { 153 returnValue = v; 154 } 155 156 /** 157 * Returns the maximum number of local variables of this frame. 158 * 159 * @return the maximum number of local variables of this frame. 160 */ 161 public int getLocals() { 162 return locals; 163 } 164 165 /** 166 * Returns the maximum stack size of this frame. 167 * 168 * @return the maximum stack size of this frame. 169 */ 170 public int getMaxStackSize() { 171 return values.length - locals; 172 } 173 174 /** 175 * Returns the value of the given local variable. 176 * 177 * @param i 178 * a local variable index. 179 * @return the value of the given local variable. 180 * @throws IndexOutOfBoundsException 181 * if the variable does not exist. 182 */ 183 public V getLocal(final int i) throws IndexOutOfBoundsException { 184 if (i >= locals) { 185 throw new IndexOutOfBoundsException( 186 "Trying to access an inexistant local variable"); 187 } 188 return values[i]; 189 } 190 191 /** 192 * Sets the value of the given local variable. 193 * 194 * @param i 195 * a local variable index. 196 * @param value 197 * the new value of this local variable. 198 * @throws IndexOutOfBoundsException 199 * if the variable does not exist. 200 */ 201 public void setLocal(final int i, final V value) 202 throws IndexOutOfBoundsException { 203 if (i >= locals) { 204 throw new IndexOutOfBoundsException( 205 "Trying to access an inexistant local variable " + i); 206 } 207 values[i] = value; 208 } 209 210 /** 211 * Returns the number of values in the operand stack of this frame. Long and 212 * double values are treated as single values. 213 * 214 * @return the number of values in the operand stack of this frame. 215 */ 216 public int getStackSize() { 217 return top; 218 } 219 220 /** 221 * Returns the value of the given operand stack slot. 222 * 223 * @param i 224 * the index of an operand stack slot. 225 * @return the value of the given operand stack slot. 226 * @throws IndexOutOfBoundsException 227 * if the operand stack slot does not exist. 228 */ 229 public V getStack(final int i) throws IndexOutOfBoundsException { 230 return values[i + locals]; 231 } 232 233 /** 234 * Clears the operand stack of this frame. 235 */ 236 public void clearStack() { 237 top = 0; 238 } 239 240 /** 241 * Pops a value from the operand stack of this frame. 242 * 243 * @return the value that has been popped from the stack. 244 * @throws IndexOutOfBoundsException 245 * if the operand stack is empty. 246 */ 247 public V pop() throws IndexOutOfBoundsException { 248 if (top == 0) { 249 throw new IndexOutOfBoundsException( 250 "Cannot pop operand off an empty stack."); 251 } 252 return values[--top + locals]; 253 } 254 255 /** 256 * Pushes a value into the operand stack of this frame. 257 * 258 * @param value 259 * the value that must be pushed into the stack. 260 * @throws IndexOutOfBoundsException 261 * if the operand stack is full. 262 */ 263 public void push(final V value) throws IndexOutOfBoundsException { 264 if (top + locals >= values.length) { 265 throw new IndexOutOfBoundsException( 266 "Insufficient maximum stack size."); 267 } 268 values[top++ + locals] = value; 269 } 270 271 public void execute(final AbstractInsnNode insn, 272 final Interpreter<V> interpreter) throws AnalyzerException { 273 V value1, value2, value3, value4; 274 List<V> values; 275 int var; 276 277 switch (insn.getOpcode()) { 278 case Opcodes.NOP: 279 break; 280 case Opcodes.ACONST_NULL: 281 case Opcodes.ICONST_M1: 282 case Opcodes.ICONST_0: 283 case Opcodes.ICONST_1: 284 case Opcodes.ICONST_2: 285 case Opcodes.ICONST_3: 286 case Opcodes.ICONST_4: 287 case Opcodes.ICONST_5: 288 case Opcodes.LCONST_0: 289 case Opcodes.LCONST_1: 290 case Opcodes.FCONST_0: 291 case Opcodes.FCONST_1: 292 case Opcodes.FCONST_2: 293 case Opcodes.DCONST_0: 294 case Opcodes.DCONST_1: 295 case Opcodes.BIPUSH: 296 case Opcodes.SIPUSH: 297 case Opcodes.LDC: 298 push(interpreter.newOperation(insn)); 299 break; 300 case Opcodes.ILOAD: 301 case Opcodes.LLOAD: 302 case Opcodes.FLOAD: 303 case Opcodes.DLOAD: 304 case Opcodes.ALOAD: 305 push(interpreter.copyOperation(insn, 306 getLocal(((VarInsnNode) insn).var))); 307 break; 308 case Opcodes.IALOAD: 309 case Opcodes.LALOAD: 310 case Opcodes.FALOAD: 311 case Opcodes.DALOAD: 312 case Opcodes.AALOAD: 313 case Opcodes.BALOAD: 314 case Opcodes.CALOAD: 315 case Opcodes.SALOAD: 316 value2 = pop(); 317 value1 = pop(); 318 push(interpreter.binaryOperation(insn, value1, value2)); 319 break; 320 case Opcodes.ISTORE: 321 case Opcodes.LSTORE: 322 case Opcodes.FSTORE: 323 case Opcodes.DSTORE: 324 case Opcodes.ASTORE: 325 value1 = interpreter.copyOperation(insn, pop()); 326 var = ((VarInsnNode) insn).var; 327 setLocal(var, value1); 328 if (value1.getSize() == 2) { 329 setLocal(var + 1, interpreter.newValue(null)); 330 } 331 if (var > 0) { 332 Value local = getLocal(var - 1); 333 if (local != null && local.getSize() == 2) { 334 setLocal(var - 1, interpreter.newValue(null)); 335 } 336 } 337 break; 338 case Opcodes.IASTORE: 339 case Opcodes.LASTORE: 340 case Opcodes.FASTORE: 341 case Opcodes.DASTORE: 342 case Opcodes.AASTORE: 343 case Opcodes.BASTORE: 344 case Opcodes.CASTORE: 345 case Opcodes.SASTORE: 346 value3 = pop(); 347 value2 = pop(); 348 value1 = pop(); 349 interpreter.ternaryOperation(insn, value1, value2, value3); 350 break; 351 case Opcodes.POP: 352 if (pop().getSize() == 2) { 353 throw new AnalyzerException(insn, "Illegal use of POP"); 354 } 355 break; 356 case Opcodes.POP2: 357 if (pop().getSize() == 1) { 358 if (pop().getSize() != 1) { 359 throw new AnalyzerException(insn, "Illegal use of POP2"); 360 } 361 } 362 break; 363 case Opcodes.DUP: 364 value1 = pop(); 365 if (value1.getSize() != 1) { 366 throw new AnalyzerException(insn, "Illegal use of DUP"); 367 } 368 push(value1); 369 push(interpreter.copyOperation(insn, value1)); 370 break; 371 case Opcodes.DUP_X1: 372 value1 = pop(); 373 value2 = pop(); 374 if (value1.getSize() != 1 || value2.getSize() != 1) { 375 throw new AnalyzerException(insn, "Illegal use of DUP_X1"); 376 } 377 push(interpreter.copyOperation(insn, value1)); 378 push(value2); 379 push(value1); 380 break; 381 case Opcodes.DUP_X2: 382 value1 = pop(); 383 if (value1.getSize() == 1) { 384 value2 = pop(); 385 if (value2.getSize() == 1) { 386 value3 = pop(); 387 if (value3.getSize() == 1) { 388 push(interpreter.copyOperation(insn, value1)); 389 push(value3); 390 push(value2); 391 push(value1); 392 break; 393 } 394 } else { 395 push(interpreter.copyOperation(insn, value1)); 396 push(value2); 397 push(value1); 398 break; 399 } 400 } 401 throw new AnalyzerException(insn, "Illegal use of DUP_X2"); 402 case Opcodes.DUP2: 403 value1 = pop(); 404 if (value1.getSize() == 1) { 405 value2 = pop(); 406 if (value2.getSize() == 1) { 407 push(value2); 408 push(value1); 409 push(interpreter.copyOperation(insn, value2)); 410 push(interpreter.copyOperation(insn, value1)); 411 break; 412 } 413 } else { 414 push(value1); 415 push(interpreter.copyOperation(insn, value1)); 416 break; 417 } 418 throw new AnalyzerException(insn, "Illegal use of DUP2"); 419 case Opcodes.DUP2_X1: 420 value1 = pop(); 421 if (value1.getSize() == 1) { 422 value2 = pop(); 423 if (value2.getSize() == 1) { 424 value3 = pop(); 425 if (value3.getSize() == 1) { 426 push(interpreter.copyOperation(insn, value2)); 427 push(interpreter.copyOperation(insn, value1)); 428 push(value3); 429 push(value2); 430 push(value1); 431 break; 432 } 433 } 434 } else { 435 value2 = pop(); 436 if (value2.getSize() == 1) { 437 push(interpreter.copyOperation(insn, value1)); 438 push(value2); 439 push(value1); 440 break; 441 } 442 } 443 throw new AnalyzerException(insn, "Illegal use of DUP2_X1"); 444 case Opcodes.DUP2_X2: 445 value1 = pop(); 446 if (value1.getSize() == 1) { 447 value2 = pop(); 448 if (value2.getSize() == 1) { 449 value3 = pop(); 450 if (value3.getSize() == 1) { 451 value4 = pop(); 452 if (value4.getSize() == 1) { 453 push(interpreter.copyOperation(insn, value2)); 454 push(interpreter.copyOperation(insn, value1)); 455 push(value4); 456 push(value3); 457 push(value2); 458 push(value1); 459 break; 460 } 461 } else { 462 push(interpreter.copyOperation(insn, value2)); 463 push(interpreter.copyOperation(insn, value1)); 464 push(value3); 465 push(value2); 466 push(value1); 467 break; 468 } 469 } 470 } else { 471 value2 = pop(); 472 if (value2.getSize() == 1) { 473 value3 = pop(); 474 if (value3.getSize() == 1) { 475 push(interpreter.copyOperation(insn, value1)); 476 push(value3); 477 push(value2); 478 push(value1); 479 break; 480 } 481 } else { 482 push(interpreter.copyOperation(insn, value1)); 483 push(value2); 484 push(value1); 485 break; 486 } 487 } 488 throw new AnalyzerException(insn, "Illegal use of DUP2_X2"); 489 case Opcodes.SWAP: 490 value2 = pop(); 491 value1 = pop(); 492 if (value1.getSize() != 1 || value2.getSize() != 1) { 493 throw new AnalyzerException(insn, "Illegal use of SWAP"); 494 } 495 push(interpreter.copyOperation(insn, value2)); 496 push(interpreter.copyOperation(insn, value1)); 497 break; 498 case Opcodes.IADD: 499 case Opcodes.LADD: 500 case Opcodes.FADD: 501 case Opcodes.DADD: 502 case Opcodes.ISUB: 503 case Opcodes.LSUB: 504 case Opcodes.FSUB: 505 case Opcodes.DSUB: 506 case Opcodes.IMUL: 507 case Opcodes.LMUL: 508 case Opcodes.FMUL: 509 case Opcodes.DMUL: 510 case Opcodes.IDIV: 511 case Opcodes.LDIV: 512 case Opcodes.FDIV: 513 case Opcodes.DDIV: 514 case Opcodes.IREM: 515 case Opcodes.LREM: 516 case Opcodes.FREM: 517 case Opcodes.DREM: 518 value2 = pop(); 519 value1 = pop(); 520 push(interpreter.binaryOperation(insn, value1, value2)); 521 break; 522 case Opcodes.INEG: 523 case Opcodes.LNEG: 524 case Opcodes.FNEG: 525 case Opcodes.DNEG: 526 push(interpreter.unaryOperation(insn, pop())); 527 break; 528 case Opcodes.ISHL: 529 case Opcodes.LSHL: 530 case Opcodes.ISHR: 531 case Opcodes.LSHR: 532 case Opcodes.IUSHR: 533 case Opcodes.LUSHR: 534 case Opcodes.IAND: 535 case Opcodes.LAND: 536 case Opcodes.IOR: 537 case Opcodes.LOR: 538 case Opcodes.IXOR: 539 case Opcodes.LXOR: 540 value2 = pop(); 541 value1 = pop(); 542 push(interpreter.binaryOperation(insn, value1, value2)); 543 break; 544 case Opcodes.IINC: 545 var = ((IincInsnNode) insn).var; 546 setLocal(var, interpreter.unaryOperation(insn, getLocal(var))); 547 break; 548 case Opcodes.I2L: 549 case Opcodes.I2F: 550 case Opcodes.I2D: 551 case Opcodes.L2I: 552 case Opcodes.L2F: 553 case Opcodes.L2D: 554 case Opcodes.F2I: 555 case Opcodes.F2L: 556 case Opcodes.F2D: 557 case Opcodes.D2I: 558 case Opcodes.D2L: 559 case Opcodes.D2F: 560 case Opcodes.I2B: 561 case Opcodes.I2C: 562 case Opcodes.I2S: 563 push(interpreter.unaryOperation(insn, pop())); 564 break; 565 case Opcodes.LCMP: 566 case Opcodes.FCMPL: 567 case Opcodes.FCMPG: 568 case Opcodes.DCMPL: 569 case Opcodes.DCMPG: 570 value2 = pop(); 571 value1 = pop(); 572 push(interpreter.binaryOperation(insn, value1, value2)); 573 break; 574 case Opcodes.IFEQ: 575 case Opcodes.IFNE: 576 case Opcodes.IFLT: 577 case Opcodes.IFGE: 578 case Opcodes.IFGT: 579 case Opcodes.IFLE: 580 interpreter.unaryOperation(insn, pop()); 581 break; 582 case Opcodes.IF_ICMPEQ: 583 case Opcodes.IF_ICMPNE: 584 case Opcodes.IF_ICMPLT: 585 case Opcodes.IF_ICMPGE: 586 case Opcodes.IF_ICMPGT: 587 case Opcodes.IF_ICMPLE: 588 case Opcodes.IF_ACMPEQ: 589 case Opcodes.IF_ACMPNE: 590 value2 = pop(); 591 value1 = pop(); 592 interpreter.binaryOperation(insn, value1, value2); 593 break; 594 case Opcodes.GOTO: 595 break; 596 case Opcodes.JSR: 597 push(interpreter.newOperation(insn)); 598 break; 599 case Opcodes.RET: 600 break; 601 case Opcodes.TABLESWITCH: 602 case Opcodes.LOOKUPSWITCH: 603 interpreter.unaryOperation(insn, pop()); 604 break; 605 case Opcodes.IRETURN: 606 case Opcodes.LRETURN: 607 case Opcodes.FRETURN: 608 case Opcodes.DRETURN: 609 case Opcodes.ARETURN: 610 value1 = pop(); 611 interpreter.unaryOperation(insn, value1); 612 interpreter.returnOperation(insn, value1, returnValue); 613 break; 614 case Opcodes.RETURN: 615 if (returnValue != null) { 616 throw new AnalyzerException(insn, "Incompatible return type"); 617 } 618 break; 619 case Opcodes.GETSTATIC: 620 push(interpreter.newOperation(insn)); 621 break; 622 case Opcodes.PUTSTATIC: 623 interpreter.unaryOperation(insn, pop()); 624 break; 625 case Opcodes.GETFIELD: 626 push(interpreter.unaryOperation(insn, pop())); 627 break; 628 case Opcodes.PUTFIELD: 629 value2 = pop(); 630 value1 = pop(); 631 interpreter.binaryOperation(insn, value1, value2); 632 break; 633 case Opcodes.INVOKEVIRTUAL: 634 case Opcodes.INVOKESPECIAL: 635 case Opcodes.INVOKESTATIC: 636 case Opcodes.INVOKEINTERFACE: { 637 values = new ArrayList<V>(); 638 String desc = ((MethodInsnNode) insn).desc; 639 for (int i = Type.getArgumentTypes(desc).length; i > 0; --i) { 640 values.add(0, pop()); 641 } 642 if (insn.getOpcode() != Opcodes.INVOKESTATIC) { 643 values.add(0, pop()); 644 } 645 if (Type.getReturnType(desc) == Type.VOID_TYPE) { 646 interpreter.naryOperation(insn, values); 647 } else { 648 push(interpreter.naryOperation(insn, values)); 649 } 650 break; 651 } 652 case Opcodes.INVOKEDYNAMIC: { 653 values = new ArrayList<V>(); 654 String desc = ((InvokeDynamicInsnNode) insn).desc; 655 for (int i = Type.getArgumentTypes(desc).length; i > 0; --i) { 656 values.add(0, pop()); 657 } 658 if (Type.getReturnType(desc) == Type.VOID_TYPE) { 659 interpreter.naryOperation(insn, values); 660 } else { 661 push(interpreter.naryOperation(insn, values)); 662 } 663 break; 664 } 665 case Opcodes.NEW: 666 push(interpreter.newOperation(insn)); 667 break; 668 case Opcodes.NEWARRAY: 669 case Opcodes.ANEWARRAY: 670 case Opcodes.ARRAYLENGTH: 671 push(interpreter.unaryOperation(insn, pop())); 672 break; 673 case Opcodes.ATHROW: 674 interpreter.unaryOperation(insn, pop()); 675 break; 676 case Opcodes.CHECKCAST: 677 case Opcodes.INSTANCEOF: 678 push(interpreter.unaryOperation(insn, pop())); 679 break; 680 case Opcodes.MONITORENTER: 681 case Opcodes.MONITOREXIT: 682 interpreter.unaryOperation(insn, pop()); 683 break; 684 case Opcodes.MULTIANEWARRAY: 685 values = new ArrayList<V>(); 686 for (int i = ((MultiANewArrayInsnNode) insn).dims; i > 0; --i) { 687 values.add(0, pop()); 688 } 689 push(interpreter.naryOperation(insn, values)); 690 break; 691 case Opcodes.IFNULL: 692 case Opcodes.IFNONNULL: 693 interpreter.unaryOperation(insn, pop()); 694 break; 695 default: 696 throw new RuntimeException("Illegal opcode " + insn.getOpcode()); 697 } 698 } 699 700 /** 701 * Merges this frame with the given frame. 702 * 703 * @param frame 704 * a frame. 705 * @param interpreter 706 * the interpreter used to merge values. 707 * @return <tt>true</tt> if this frame has been changed as a result of the 708 * merge operation, or <tt>false</tt> otherwise. 709 * @throws AnalyzerException 710 * if the frames have incompatible sizes. 711 */ 712 public boolean merge(final Frame<? extends V> frame, 713 final Interpreter<V> interpreter) throws AnalyzerException { 714 if (top != frame.top) { 715 throw new AnalyzerException(null, "Incompatible stack heights"); 716 } 717 boolean changes = false; 718 for (int i = 0; i < locals + top; ++i) { 719 V v = interpreter.merge(values[i], frame.values[i]); 720 if (!v.equals(values[i])) { 721 values[i] = v; 722 changes = true; 723 } 724 } 725 return changes; 726 } 727 728 /** 729 * Merges this frame with the given frame (case of a RET instruction). 730 * 731 * @param frame 732 * a frame 733 * @param access 734 * the local variables that have been accessed by the subroutine 735 * to which the RET instruction corresponds. 736 * @return <tt>true</tt> if this frame has been changed as a result of the 737 * merge operation, or <tt>false</tt> otherwise. 738 */ 739 public boolean merge(final Frame<? extends V> frame, final boolean[] access) { 740 boolean changes = false; 741 for (int i = 0; i < locals; ++i) { 742 if (!access[i] && !values[i].equals(frame.values[i])) { 743 values[i] = frame.values[i]; 744 changes = true; 745 } 746 } 747 return changes; 748 } 749 750 /** 751 * Returns a string representation of this frame. 752 * 753 * @return a string representation of this frame. 754 */ 755 @Override 756 public String toString() { 757 StringBuilder sb = new StringBuilder(); 758 for (int i = 0; i < getLocals(); ++i) { 759 sb.append(getLocal(i)); 760 } 761 sb.append(' '); 762 for (int i = 0; i < getStackSize(); ++i) { 763 sb.append(getStack(i).toString()); 764 } 765 return sb.toString(); 766 } 767 }