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.classfile.constantpool.NameAndTypeEntry;
34 import java.lang.constant.ClassDesc;
35 import java.util.List;
36
37 import jdk.internal.classfile.impl.StackMapDecoder;
38 import jdk.internal.classfile.impl.TemporaryConstantPool;
39
40 /**
41 * Models a stack map frame in a {@link StackMapTableAttribute StackMapTable}
42 * attribute (JVMS {@jvms 4.7.4}). A stack map frame must appear at the
43 * beginning of each basic block in a method (JVMS {@jvms 4.10.1}).
44 *
45 * @apiNote
46 * In general, a stack map frame should be defined for each target of a
47 * {@link BranchInstruction}, or unreachable code right after an unconditional
48 * branch instruction like {@link Opcode#GOTO goto}. The automatic stack map
49 * generation cannot handle unreachable code right after an unconditional jump;
50 * The {@link ClassFile.DeadCodeOption} allows substituting such code, or
51 * advanced users can provide their own stack maps for dead code.
52 *
53 * @see StackMapTableAttribute#entries()
54 * @jvms 4.7.4 The {@code StackMapTable} Attribute
55 * @jvms 4.10.1 Verification by Type Checking
56 * @since 24
57 */
58 public sealed interface StackMapFrameInfo
59 permits StackMapDecoder.StackMapFrameImpl {
60
61 /**
62 * {@return the raw {@code u1 frame_type}}
63 */
64 int frameType();
65
66 /**
67 * {@return the frame target label}
68 */
69 Label target();
70
71 /**
72 * {@return the expanded local variable types}
73 */
74 List<VerificationTypeInfo> locals();
75
76 /**
77 * {@return the expanded operand stack types}
78 */
79 List<VerificationTypeInfo> stack();
80
81 /**
82 * {@return the expanded unset fields}
83 *
84 * @see <a href="https://cr.openjdk.org/~dlsmith/jep401/jep401-20250409/specs/strict-fields-jvms.html">Specs</a>
85 */
86 List<NameAndTypeEntry> unsetFields();
87
88 /**
89 * {@return a new stack map frame}
90 *
91 * @param target the location of the frame
92 * @param locals the complete list of frame locals
93 * @param stack the complete frame stack
94 */
95 public static StackMapFrameInfo of(Label target,
96 List<VerificationTypeInfo> locals,
97 List<VerificationTypeInfo> stack) {
98
99 return of(target, locals, stack, List.of());
100 }
101
102 /**
103 * {@return a new stack map frame}
104 * @param target the location of the frame
105 * @param locals the complete list of frame locals
106 * @param stack the complete frame stack
107 * @param unsetFields the complete list of unset fields
108 * @throws IllegalArgumentException if unset fields has entries but no
109 * {@link SimpleVerificationTypeInfo#UNINITIALIZED_THIS uninitializedThis}
110 * is present in {@code locals}
111 */
112 public static StackMapFrameInfo of(Label target,
113 List<VerificationTypeInfo> locals,
114 List<VerificationTypeInfo> stack,
115 List<NameAndTypeEntry> unsetFields) {
116
117 return new StackMapDecoder.StackMapFrameImpl(255, target, locals, stack, unsetFields);
118 }
119
120 /**
121 * The type of a stack or local variable value.
122 *
123 * @see #locals()
124 * @see #stack()
125 * @jvms 4.7.4 The {@code StackMapTable} Attribute
126 * @since 24
127 */
128 sealed interface VerificationTypeInfo {
129
130 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#TOP TOP}. */
131 int ITEM_TOP = 0;
132
133 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#INTEGER INTEGER}. */
134 int ITEM_INTEGER = 1;
135
136 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#FLOAT FLOAT}. */
137 int ITEM_FLOAT = 2;
138
139 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#DOUBLE DOUBLE}. */
140 int ITEM_DOUBLE = 3;
141
142 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#LONG LONG}. */
143 int ITEM_LONG = 4;
144
145 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#NULL NULL}. */
146 int ITEM_NULL = 5;
147
148 /** The {@link #tag() tag} for verification type info {@link SimpleVerificationTypeInfo#UNINITIALIZED_THIS UNINITIALIZED_THIS}. */
149 int ITEM_UNINITIALIZED_THIS = 6;
150
151 /** The {@link #tag() tag} for verification type info {@link ObjectVerificationTypeInfo OBJECT}. */
152 int ITEM_OBJECT = 7;
153
154 /** The {@link #tag() tag} for verification type info {@link UninitializedVerificationTypeInfo UNINITIALIZED}. */
155 int ITEM_UNINITIALIZED = 8;
156
157 /**
158 * {@return the tag of the type info}
159 *
160 * @apiNote
161 * {@code ITEM_}-prefixed constants in this class, such as {@link #ITEM_TOP}, describe the
162 * possible return values of this method.
163 */
164 int tag();
165 }
166
167 /**
168 * A simple stack value.
169 *
170 * @since 24
171 */
172 public enum SimpleVerificationTypeInfo implements VerificationTypeInfo {
173
174 /** Verification type top. */
175 TOP(ITEM_TOP),
176
177 /** Verification type int. */
178 INTEGER(ITEM_INTEGER),
179
180 /** Verification type float. */
181 FLOAT(ITEM_FLOAT),
182
183 /** Verification type double. */
184 DOUBLE(ITEM_DOUBLE),
185
186 /** Verification type long. */
187 LONG(ITEM_LONG),
188
189 /** Verification type null. */
190 NULL(ITEM_NULL),
191
192 /** Verification type uninitializedThis. */
193 UNINITIALIZED_THIS(ITEM_UNINITIALIZED_THIS);
194
195
196 private final int tag;
197
198 SimpleVerificationTypeInfo(int tag) {
199 this.tag = tag;
200 }
201
202 @Override
203 public int tag() {
204 return tag;
205 }
206 }
207
208 /**
209 * A stack value for an object type. Its {@link #tag() tag} is {@value #ITEM_OBJECT}.
210 *
211 * @jvms 4.7.4 The {@code StackMapTable} Attribute
212 * @since 24
213 */
214 sealed interface ObjectVerificationTypeInfo extends VerificationTypeInfo
215 permits StackMapDecoder.ObjectVerificationTypeInfoImpl {
216
217 /**
218 * {@return a new object verification type info}
219 * @param className the class of the object
220 */
221 public static ObjectVerificationTypeInfo of(ClassEntry className) {
222 return new StackMapDecoder.ObjectVerificationTypeInfoImpl(className);
223 }
224
225 /**
226 * {@return a new object verification type info}
227 * @param classDesc the class of the object
228 * @throws IllegalArgumentException if {@code classDesc} represents a primitive type
229 */
230 public static ObjectVerificationTypeInfo of(ClassDesc classDesc) {
231 return of(TemporaryConstantPool.INSTANCE.classEntry(classDesc));
232 }
233
234 /**
235 * {@return the class of the object}
236 */
237 ClassEntry className();
238
239 /**
240 * {@return the class of the object, as a symbolic descriptor}
241 */
242 default ClassDesc classSymbol() {
243 return className().asSymbol();
244 }
245 }
246
247 /**
248 * An uninitialized stack value. Its {@link #tag() tag} is {@value #ITEM_UNINITIALIZED}.
249 *
250 * @jvms 4.7.4 The {@code StackMapTable} Attribute
251 * @since 24
252 */
253 sealed interface UninitializedVerificationTypeInfo extends VerificationTypeInfo
254 permits StackMapDecoder.UninitializedVerificationTypeInfoImpl {
255
256 /**
257 * {@return the label immediately before the {@link Opcode#NEW new}
258 * instruction that creates this uninitialized object}
259 */
260 Label newTarget();
261
262 /**
263 * {@return an uninitialized verification type info}
264 * @param newTarget the label immediately before the {@link Opcode#NEW new}
265 * instruction that creates this uninitialized object
266 */
267 public static UninitializedVerificationTypeInfo of(Label newTarget) {
268 return new StackMapDecoder.UninitializedVerificationTypeInfoImpl(newTarget);
269 }
270 }
271 }