changeset 1928:99b60bcf3862

8022186: javac generates dead code if a try with an empty body has a finalizer Reviewed-by: jjg
author vromero
date Tue, 06 Aug 2013 15:08:49 +0100
parents 05370ef9dccb
children 051e64d0816e f3ea20a6e958
files src/share/classes/com/sun/tools/javac/jvm/Gen.java test/tools/javac/T8022186/DeadCodeGeneratedForEmptyTryTest.java
diffstat 2 files changed, 231 insertions(+), 57 deletions(-) [+]
line wrap: on
line diff
--- a/src/share/classes/com/sun/tools/javac/jvm/Gen.java	Wed Jul 31 08:37:34 2013 -0700
+++ b/src/share/classes/com/sun/tools/javac/jvm/Gen.java	Tue Aug 06 15:08:49 2013 +0100
@@ -1478,74 +1478,82 @@
             code.statBegin(TreeInfo.endPos(body));
             genFinalizer(env);
             code.statBegin(TreeInfo.endPos(env.tree));
-            Chain exitChain = code.branch(goto_);
+            Chain exitChain;
+            if (startpc != endpc) {
+                exitChain = code.branch(goto_);
+            } else {
+                exitChain = code.branch(dontgoto);
+            }
             endFinalizerGap(env);
-            if (startpc != endpc) for (List<JCCatch> l = catchers; l.nonEmpty(); l = l.tail) {
-                // start off with exception on stack
-                code.entryPoint(stateTry, l.head.param.sym.type);
-                genCatch(l.head, env, startpc, endpc, gaps);
-                genFinalizer(env);
-                if (hasFinalizer || l.tail.nonEmpty()) {
-                    code.statBegin(TreeInfo.endPos(env.tree));
-                    exitChain = Code.mergeChains(exitChain,
-                                                 code.branch(goto_));
+            if (startpc != endpc) {
+                for (List<JCCatch> l = catchers; l.nonEmpty(); l = l.tail) {
+                    // start off with exception on stack
+                    code.entryPoint(stateTry, l.head.param.sym.type);
+                    genCatch(l.head, env, startpc, endpc, gaps);
+                    genFinalizer(env);
+                    if (hasFinalizer || l.tail.nonEmpty()) {
+                        code.statBegin(TreeInfo.endPos(env.tree));
+                        exitChain = Code.mergeChains(exitChain,
+                                                     code.branch(goto_));
+                    }
+                    endFinalizerGap(env);
                 }
-                endFinalizerGap(env);
-            }
-            if (hasFinalizer) {
-                // Create a new register segement to avoid allocating
-                // the same variables in finalizers and other statements.
-                code.newRegSegment();
 
-                // Add a catch-all clause.
+                if (hasFinalizer) {
+                    // Create a new register segement to avoid allocating
+                    // the same variables in finalizers and other statements.
+                    code.newRegSegment();
 
-                // start off with exception on stack
-                int catchallpc = code.entryPoint(stateTry, syms.throwableType);
+                    // Add a catch-all clause.
 
-                // Register all exception ranges for catch all clause.
-                // The range of the catch all clause is from the beginning
-                // of the try or synchronized block until the present
-                // code pointer excluding all gaps in the current
-                // environment's GenContext.
-                int startseg = startpc;
-                while (env.info.gaps.nonEmpty()) {
-                    int endseg = env.info.gaps.next().intValue();
-                    registerCatch(body.pos(), startseg, endseg,
-                                  catchallpc, 0);
-                    startseg = env.info.gaps.next().intValue();
-                }
-                code.statBegin(TreeInfo.finalizerPos(env.tree));
-                code.markStatBegin();
+                    // start off with exception on stack
+                    int catchallpc = code.entryPoint(stateTry, syms.throwableType);
 
-                Item excVar = makeTemp(syms.throwableType);
-                excVar.store();
-                genFinalizer(env);
-                excVar.load();
-                registerCatch(body.pos(), startseg,
-                              env.info.gaps.next().intValue(),
-                              catchallpc, 0);
-                code.emitop0(athrow);
-                code.markDead();
-
-                // If there are jsr's to this finalizer, ...
-                if (env.info.cont != null) {
-                    // Resolve all jsr's.
-                    code.resolve(env.info.cont);
-
-                    // Mark statement line number
+                    // Register all exception ranges for catch all clause.
+                    // The range of the catch all clause is from the beginning
+                    // of the try or synchronized block until the present
+                    // code pointer excluding all gaps in the current
+                    // environment's GenContext.
+                    int startseg = startpc;
+                    while (env.info.gaps.nonEmpty()) {
+                        int endseg = env.info.gaps.next().intValue();
+                        registerCatch(body.pos(), startseg, endseg,
+                                      catchallpc, 0);
+                        startseg = env.info.gaps.next().intValue();
+                    }
                     code.statBegin(TreeInfo.finalizerPos(env.tree));
                     code.markStatBegin();
 
-                    // Save return address.
-                    LocalItem retVar = makeTemp(syms.throwableType);
-                    retVar.store();
+                    Item excVar = makeTemp(syms.throwableType);
+                    excVar.store();
+                    genFinalizer(env);
+                    excVar.load();
+                    registerCatch(body.pos(), startseg,
+                                  env.info.gaps.next().intValue(),
+                                  catchallpc, 0);
+                    code.emitop0(athrow);
+                    code.markDead();
 
-                    // Generate finalizer code.
-                    env.info.finalize.genLast();
+                    // If there are jsr's to this finalizer, ...
+                    if (env.info.cont != null) {
+                        // Resolve all jsr's.
+                        code.resolve(env.info.cont);
 
-                    // Return.
-                    code.emitop1w(ret, retVar.reg);
-                    code.markDead();
+                        // Mark statement line number
+                        code.statBegin(TreeInfo.finalizerPos(env.tree));
+                        code.markStatBegin();
+
+                        // Save return address.
+                        LocalItem retVar = makeTemp(syms.throwableType);
+                        retVar.store();
+
+                        // Generate finalizer code.
+                        env.info.finalize.genLast();
+
+                        // Return.
+                        code.emitop1w(ret, retVar.reg);
+                        code.markDead();
+                    }
                 }
             }
             // Resolve all breaks.
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javac/T8022186/DeadCodeGeneratedForEmptyTryTest.java	Tue Aug 06 15:08:49 2013 +0100
@@ -0,0 +1,166 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8022186
+ * @summary javac generates dead code if a try with an empty body has a finalizer
+ */
+
+import com.sun.tools.classfile.Attribute;
+import com.sun.tools.classfile.ClassFile;
+import com.sun.tools.classfile.Code_attribute;
+import com.sun.tools.classfile.ConstantPool;
+import com.sun.tools.classfile.ConstantPool.CONSTANT_String_info;
+import com.sun.tools.classfile.ConstantPool.CPInfo;
+import com.sun.tools.classfile.ConstantPool.InvalidIndex;
+import com.sun.tools.classfile.Instruction;
+import com.sun.tools.classfile.Instruction.KindVisitor;
+import com.sun.tools.classfile.Instruction.TypeKind;
+import com.sun.tools.classfile.Method;
+import com.sun.tools.javac.util.Assert;
+import java.io.BufferedInputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public class DeadCodeGeneratedForEmptyTryTest {
+
+    public static void main(String[] args) throws Exception {
+        new DeadCodeGeneratedForEmptyTryTest().run();
+    }
+
+    void run() throws Exception {
+        checkClassFile(Paths.get(System.getProperty("test.classes"),
+                this.getClass().getName() + "$Test.class"));
+    }
+
+    int utf8Index;
+    int numberOfRefToStr = 0;
+    ConstantPool constantPool;
+
+    void checkClassFile(final Path path) throws Exception {
+        ClassFile classFile = ClassFile.read(
+                new BufferedInputStream(Files.newInputStream(path)));
+        constantPool = classFile.constant_pool;
+        utf8Index = constantPool.getUTF8Index("STR_TO_LOOK_FOR");
+        for (Method method: classFile.methods) {
+            if (method.getName(constantPool).equals("methodToLookFor")) {
+                Code_attribute codeAtt = (Code_attribute)method.attributes.get(Attribute.Code);
+                for (Instruction inst: codeAtt.getInstructions()) {
+                    inst.accept(codeVisitor, null);
+                }
+            }
+        }
+        Assert.check(numberOfRefToStr == 1,
+                "There should only be one reference to a CONSTANT_String_info structure in the generated code");
+    }
+
+    CodeVisitor codeVisitor = new CodeVisitor();
+
+    class CodeVisitor implements KindVisitor<Void, Void> {
+
+        void checkIndirectRefToString(int cp_index) {
+            try {
+                CPInfo cInfo = constantPool.get(cp_index);
+                if (cInfo instanceof CONSTANT_String_info) {
+                    CONSTANT_String_info strInfo = (CONSTANT_String_info)cInfo;
+                    if (strInfo.string_index == utf8Index) {
+                        numberOfRefToStr++;
+                    }
+                }
+            } catch (InvalidIndex ex) {
+                throw new AssertionError("invalid constant pool index at " + cp_index);
+            }
+        }
+
+        @Override
+        public Void visitNoOperands(Instruction instr, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitArrayType(Instruction instr, TypeKind kind, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitBranch(Instruction instr, int offset, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitConstantPoolRef(Instruction instr, int index, Void p) {
+            checkIndirectRefToString(index);
+            return null;
+        }
+
+        @Override
+        public Void visitConstantPoolRefAndValue(Instruction instr, int index, int value, Void p) {
+            checkIndirectRefToString(index);
+            return null;
+        }
+
+        @Override
+        public Void visitLocal(Instruction instr, int index, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitLocalAndValue(Instruction instr, int index, int value, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitLookupSwitch(Instruction instr, int default_, int npairs, int[] matches, int[] offsets, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitTableSwitch(Instruction instr, int default_, int low, int high, int[] offsets, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitValue(Instruction instr, int value, Void p) {
+            return null;
+        }
+
+        @Override
+        public Void visitUnknown(Instruction instr, Void p) {
+            return null;
+        }
+
+    }
+
+    public class Test {
+        void methodToLookFor() {
+            try {
+            } finally {
+                System.out.println("STR_TO_LOOK_FOR");
+            }
+        }
+    }
+}