1 /*
2 * Copyright (c) 2023, 2025, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang.classfile.attribute;
27
28 import java.lang.classfile.ClassFile;
29 import java.lang.classfile.Label;
30 import java.lang.classfile.Opcode;
31 import java.lang.classfile.constantpool.ClassEntry;
32 import java.lang.classfile.instruction.BranchInstruction;
33 import java.lang.constant.ClassDesc;
34 import java.util.List;
35
36 import jdk.internal.classfile.impl.StackMapDecoder;
37 import jdk.internal.classfile.impl.TemporaryConstantPool;
38
39 /**
40 * Models a stack map frame in a {@link StackMapTableAttribute StackMapTable}
41 * attribute (JVMS {@jvms 4.7.4}). A stack map frame must appear at the
42 * beginning of each basic block in a method (JVMS {@jvms 4.10.1}).
43 *
44 * @apiNote
45 * In general, a stack map frame should be defined for each target of a
46 * {@link BranchInstruction}, or unreachable code right after an unconditional
47 * branch instruction like {@link Opcode#GOTO goto}. The automatic stack map
48 * generation cannot handle unreachable code right after an unconditional jump;
49 * The {@link ClassFile.DeadCodeOption} allows substituting such code, or
50 * advanced users can provide their own stack maps for dead code.
51 *
52 * @see StackMapTableAttribute#entries()
53 * @jvms 4.7.4 The {@code StackMapTable} Attribute
54 * @jvms 4.10.1 Verification by Type Checking
55 * @since 24
56 */
57 public sealed interface StackMapFrameInfo
58 permits StackMapDecoder.StackMapFrameImpl {
59
60 /**
61 * {@return the raw {@code u1 frame_type}}
62 */
63 int frameType();
64
65 /**
66 * {@return the frame target label}
67 */
68 Label target();
69
70 /**
71 * {@return the expanded local variable types}
72 */
73 List<VerificationTypeInfo> locals();
74
75 /**
76 * {@return the expanded operand stack types}
77 */
78 List<VerificationTypeInfo> stack();
79
80 /**
81 * {@return a new stack map frame}
82 *
83 * @param target the location of the frame
84 * @param locals the complete list of frame locals
85 * @param stack the complete frame stack
86 */
87 public static StackMapFrameInfo of(Label target,
88 List<VerificationTypeInfo> locals,
89 List<VerificationTypeInfo> stack) {
90 return new StackMapDecoder.StackMapFrameImpl(255, target, locals, stack);
91 }
92
93 /**
94 * The type of a stack or local variable value.
95 *
96 * @see #locals()
97 * @see #stack()
98 * @jvms 4.7.4 The {@code StackMapTable} Attribute
99 * @since 24
100 */
101 sealed interface VerificationTypeInfo {
102
103 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#TOP TOP}. */
104 int ITEM_TOP = 0;
105
106 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#INTEGER INTEGER}. */
107 int ITEM_INTEGER = 1;
108
109 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#FLOAT FLOAT}. */
110 int ITEM_FLOAT = 2;
111
112 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#DOUBLE DOUBLE}. */
113 int ITEM_DOUBLE = 3;
114
115 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#LONG LONG}. */
116 int ITEM_LONG = 4;
117
118 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#NULL NULL}. */
119 int ITEM_NULL = 5;
120
121 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#UNINITIALIZED_THIS UNINITIALIZED_THIS}. */
122 int ITEM_UNINITIALIZED_THIS = 6;
123
124 /** The {@link #tag() tag} for verification type info {@link ObjectVerificationTypeInfo OBJECT}. */
125 int ITEM_OBJECT = 7;
126
127 /** The {@link #tag() tag} for verification type info {@link UninitializedVerificationTypeInfo UNINITIALIZED}. */
128 int ITEM_UNINITIALIZED = 8;
129
130 /**
131 * {@return the tag of the type info}
132 *
133 * @apiNote
134 * {@code ITEM_}-prefixed constants in this class, such as {@link #ITEM_TOP}, describe the
135 * possible return values of this method.
136 */
137 int tag();
138 }
139
140 /**
141 * A simple stack value.
142 *
143 * @since 24
144 */
145 public enum SimpleVerificationTypeInfo implements VerificationTypeInfo {
146
147 /** Verification type top. */
148 TOP(ITEM_TOP),
149
150 /** Verification type int. */
151 INTEGER(ITEM_INTEGER),
152
153 /** Verification type float. */
154 FLOAT(ITEM_FLOAT),
155
156 /** Verification type double. */
157 DOUBLE(ITEM_DOUBLE),
158
159 /** Verification type long. */
160 LONG(ITEM_LONG),
161
162 /** Verification type null. */
163 NULL(ITEM_NULL),
164
165 /** Verification type uninitializedThis. */
166 UNINITIALIZED_THIS(ITEM_UNINITIALIZED_THIS);
167
168
169 private final int tag;
170
171 SimpleVerificationTypeInfo(int tag) {
172 this.tag = tag;
173 }
174
175 @Override
176 public int tag() {
177 return tag;
178 }
179 }
180
181 /**
182 * A stack value for an object type. Its {@link #tag() tag} is {@value #ITEM_OBJECT}.
183 *
184 * @jvms 4.7.4 The {@code StackMapTable} Attribute
185 * @since 24
186 */
187 sealed interface ObjectVerificationTypeInfo extends VerificationTypeInfo
188 permits StackMapDecoder.ObjectVerificationTypeInfoImpl {
189
190 /**
191 * {@return a new object verification type info}
192 * @param className the class of the object
193 */
194 public static ObjectVerificationTypeInfo of(ClassEntry className) {
195 return new StackMapDecoder.ObjectVerificationTypeInfoImpl(className);
196 }
197
198 /**
199 * {@return a new object verification type info}
200 * @param classDesc the class of the object
201 * @throws IllegalArgumentException if {@code classDesc} represents a primitive type
202 */
203 public static ObjectVerificationTypeInfo of(ClassDesc classDesc) {
204 return of(TemporaryConstantPool.INSTANCE.classEntry(classDesc));
205 }
206
207 /**
208 * {@return the class of the object}
209 */
210 ClassEntry className();
211
212 /**
213 * {@return the class of the object, as a symbolic descriptor}
214 */
215 default ClassDesc classSymbol() {
216 return className().asSymbol();
217 }
218 }
219
220 /**
221 * An uninitialized stack value. Its {@link #tag() tag} is {@value #ITEM_UNINITIALIZED}.
222 *
223 * @jvms 4.7.4 The {@code StackMapTable} Attribute
224 * @since 24
225 */
226 sealed interface UninitializedVerificationTypeInfo extends VerificationTypeInfo
227 permits StackMapDecoder.UninitializedVerificationTypeInfoImpl {
228
229 /**
230 * {@return the label immediately before the {@link Opcode#NEW new}
231 * instruction that creates this uninitialized object}
232 */
233 Label newTarget();
234
235 /**
236 * {@return an uninitialized verification type info}
237 * @param newTarget the label immediately before the {@link Opcode#NEW new}
238 * instruction that creates this uninitialized object
239 */
240 public static UninitializedVerificationTypeInfo of(Label newTarget) {
241 return new StackMapDecoder.UninitializedVerificationTypeInfoImpl(newTarget);
242 }
243 }
244 }