8296656: java.lang.NoClassDefFoundError exception on running fully legitimate code

8287885: Local classes cause ClassLoader error if the type names are similar but not same

Reviewed-by: vromero
(cherry picked from commit 14b970dc9e)

src/jdk.compiler/share/classes/com/sun/tools/javac/code/Lint.java

@@ -240,6 +240,11 @@ public class Lint
          */
         OPTIONS("options"),
 
+        /**
+         * Warn when any output file is written to more than once.
+         */
+        OUTPUT_FILE_CLASH("output-file-clash"),
+
         /**
          * Warn about issues regarding method overloads.
          */

src/jdk.compiler/share/classes/com/sun/tools/javac/file/BaseFileManager.java

@@ -41,6 +41,8 @@ import java.nio.charset.CoderResult;
 import java.nio.charset.CodingErrorAction;
 import java.nio.charset.IllegalCharsetNameException;
 import java.nio.charset.UnsupportedCharsetException;
+import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.util.Collection;
 import java.util.HashMap;
@@ -54,10 +56,12 @@ import javax.tools.JavaFileManager;
 import javax.tools.JavaFileObject;
 import javax.tools.JavaFileObject.Kind;
 
+import com.sun.tools.javac.code.Lint.LintCategory;
 import com.sun.tools.javac.main.Option;
 import com.sun.tools.javac.main.OptionHelper;
 import com.sun.tools.javac.main.OptionHelper.GrumpyHelper;
 import com.sun.tools.javac.resources.CompilerProperties.Errors;
+import com.sun.tools.javac.resources.CompilerProperties.Warnings;
 import com.sun.tools.javac.util.Abort;
 import com.sun.tools.javac.util.Context;
 import com.sun.tools.javac.util.DefinedBy;
@@ -87,9 +91,12 @@ public abstract class BaseFileManager implements JavaFileManager {
         options = Options.instance(context);
         classLoaderClass = options.get("procloader");
 
-        // Avoid initializing Lint
+        // Detect Lint options, but use Options.isLintSet() to avoid initializing the Lint class
         boolean warn = options.isLintSet("path");
         locations.update(log, warn, FSInfo.instance(context));
+        synchronized (this) {
+            outputFilesWritten = options.isLintSet("output-file-clash") ? new HashSet<>() : null;
+        }
 
         // Setting this option is an indication that close() should defer actually closing
         // the file manager until after a specified period of inactivity.
@@ -133,6 +140,9 @@ public abstract class BaseFileManager implements JavaFileManager {
 
     protected final Locations locations;
 
+    // This is non-null when output file clash detection is enabled
+    private HashSet<Path> outputFilesWritten;
+
     /**
      * A flag for clients to use to indicate that this file manager should
      * be closed when it is no longer required.
@@ -467,6 +477,11 @@ public abstract class BaseFileManager implements JavaFileManager {
         contentCache.remove(file);
     }
 
+    public synchronized void resetOutputFilesWritten() {
+        if (outputFilesWritten != null)
+            outputFilesWritten.clear();
+    }
+
     protected final Map<JavaFileObject, ContentCacheEntry> contentCache = new HashMap<>();
 
     protected static class ContentCacheEntry {
@@ -512,4 +527,29 @@ public abstract class BaseFileManager implements JavaFileManager {
             Objects.requireNonNull(t);
         return it;
     }
+
+// Output File Clash Detection
+
+    /** Record the fact that we have started writing to an output file.
+     */
+    // Note: individual files can be accessed concurrently, so we synchronize here
+    synchronized void newOutputToPath(Path path) throws IOException {
+
+        // Is output file clash detection enabled?
+        if (outputFilesWritten == null)
+            return;
+
+        // Get the "canonical" version of the file's path; we are assuming
+        // here that two clashing files will resolve to the same real path.
+        Path realPath;
+        try {
+            realPath = path.toRealPath();
+        } catch (NoSuchFileException e) {
+            return;         // should never happen except on broken filesystems
+        }
+
+        // Check whether we've already opened this file for output
+        if (!outputFilesWritten.add(realPath))
+            log.warning(LintCategory.OUTPUT_FILE_CLASH, Warnings.OutputFileClash(path));
+    }
 }

src/jdk.compiler/share/classes/com/sun/tools/javac/file/JavacFileManager.java

@@ -738,6 +738,7 @@ public class JavacFileManager extends BaseFileManager implements StandardJavaFil
         pathsAndContainersByLocationAndRelativeDirectory.clear();
         nonIndexingContainersByLocation.clear();
         contentCache.clear();
+        resetOutputFilesWritten();
     }
 
     @Override @DefinedBy(Api.COMPILER)

src/jdk.compiler/share/classes/com/sun/tools/javac/file/PathFileObject.java

@@ -448,7 +448,9 @@ public abstract class PathFileObject implements JavaFileObject {
         fileManager.updateLastUsedTime();
         fileManager.flushCache(this);
         ensureParentDirectoriesExist();
-        return Files.newOutputStream(path);
+        OutputStream output = Files.newOutputStream(path);
+        fileManager.newOutputToPath(path);
+        return output;
     }
 
     @Override @DefinedBy(Api.COMPILER)
@@ -483,7 +485,9 @@ public abstract class PathFileObject implements JavaFileObject {
         fileManager.updateLastUsedTime();
         fileManager.flushCache(this);
         ensureParentDirectoriesExist();
-        return new OutputStreamWriter(Files.newOutputStream(path), fileManager.getEncodingName());
+        Writer writer = new OutputStreamWriter(Files.newOutputStream(path), fileManager.getEncodingName());
+        fileManager.newOutputToPath(path);
+        return writer;
     }
 
     @Override @DefinedBy(Api.COMPILER)

src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties

@@ -1618,6 +1618,10 @@ compiler.misc.x.print.rounds=\
 compiler.warn.file.from.future=\
     Modification date is in the future for file {0}
 
+# 0: path
+compiler.warn.output.file.clash=\
+    output file written more than once: {0}
+
 #####
 
 ## The following string will appear before all messages keyed as:

src/jdk.compiler/share/classes/com/sun/tools/javac/resources/javac.properties

@@ -221,6 +221,10 @@ javac.opt.Xlint.desc.opens=\
 javac.opt.Xlint.desc.options=\
     Warn about issues relating to use of command line options.
 
+javac.opt.Xlint.desc.output-file-clash=\
+    Warn when an output file is overwritten during compilation. This can occur, for example,\n\
+\                         on case-insensitive filesystems. Covers class files, native header files, and source files.
+
 javac.opt.Xlint.desc.overloads=\
     Warn about issues regarding method overloads.
 

src/jdk.compiler/share/man/javac.1

@@ -736,6 +736,9 @@ constructors in public and protected classes in exported packages.
 \f[V]options\f[R]: Warns about the issues relating to use of command
 line options.
 .IP \[bu] 2
+\f[V]output-file-clash\f[R]: Warns if any output file is overwritten during compilation.
+This can occur, for example, on case-insensitive filesystems.
+.IP \[bu] 2
 \f[V]overloads\f[R]: Warns about the issues related to method overloads.
 .IP \[bu] 2
 \f[V]overrides\f[R]: Warns about the issues related to method overrides.

test/langtools/tools/javac/diags/examples.not-yet.txt

@@ -118,6 +118,7 @@ compiler.warn.incubating.modules                        # requires adjusted clas
 compiler.warn.invalid.archive.file
 compiler.warn.is.preview                                # difficult to produce reliably despite future changes to java.base
 compiler.warn.is.preview.reflective                     # difficult to produce reliably despite future changes to java.base
+compiler.warn.output.file.clash                         # this warning is not generated on Linux
 compiler.warn.override.bridge
 compiler.warn.position.overflow                         # CRTable: caused by files with long lines >= 1024 chars
 compiler.warn.proc.type.already.exists                  # JavacFiler: just mentioned in TODO

test/langtools/tools/javac/file/OutputFileClashTest.java

@@ -0,0 +1,139 @@
+/*
+ * Copyright (c) 2023, 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.
+ *
+ * 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 8287885 8296656 7016187
+ * @summary Verify proper function of the "output-file-clash" lint flag
+ * @requires os.family == "mac"
+ * @library /tools/lib
+ * @modules jdk.compiler/com.sun.tools.javac.api
+ *          jdk.compiler/com.sun.tools.javac.main
+ *          jdk.compiler/com.sun.tools.javac.util
+ * @build toolbox.ToolBox toolbox.JavacTask
+ * @run main OutputFileClashTest
+*/
+
+import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.regex.Pattern;
+
+import toolbox.TestRunner;
+import toolbox.ToolBox;
+import toolbox.JavacTask;
+import toolbox.Task;
+
+public class OutputFileClashTest extends TestRunner {
+
+    protected ToolBox tb;
+
+    public OutputFileClashTest() {
+        super(System.err);
+        tb = new ToolBox();
+    }
+
+    protected void runTests() throws Exception {
+        runTests(m -> new Object[] { Paths.get(m.getName()) });
+    }
+
+    Path[] findJavaFiles(Path... paths) throws IOException {
+        return tb.findJavaFiles(paths);
+    }
+
+// Note: in these tests, it's indeterminate which output file gets written first.
+// So we compare the log output to a regex that matches the error either way.
+
+    @Test
+    public void testBug8287885(Path base) throws Exception {
+        testClash(base,
+                """
+                public class Test {
+                    void method1() {
+                        enum ABC { A, B, C; };  // becomes "Test$1ABC.class"
+                    }
+                    void method2() {
+                        enum Abc { A, B, C; };  // becomes "Test$1Abc.class"
+                    }
+                }
+                """,
+            "- compiler.warn.output.file.clash: .*Test\\$1(ABC|Abc)\\.class");
+    }
+
+    @Test
+    public void testBug8296656(Path base) throws Exception {
+        testClash(base,
+                """
+                public class Test {
+                    @interface Annotation {
+                        interface foo { }
+                        @interface Foo { }
+                    }
+                }
+                """,
+            "- compiler.warn.output.file.clash: .*Test\\$Annotation\\$(foo|Foo)\\.class");
+    }
+
+    @Test
+    public void testCombiningAcuteAccent(Path base) throws Exception {
+        testClash(base,
+                """
+                public class Test {
+                    interface Cafe\u0301 {      // macos normalizes "e" + U0301 -> U00e9
+                    }
+                    interface Caf\u00e9 {
+                    }
+                }
+                """,
+            "- compiler.warn.output.file.clash: .*Test\\$Caf.*\\.class");
+    }
+
+    private void testClash(Path base, String javaSource, String regex) throws Exception {
+
+        // Compile source
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src, javaSource);
+        Path classes = base.resolve("classes");
+        tb.createDirectories(classes);
+        Path headers = base.resolve("headers");
+        tb.createDirectories(headers);
+        List<String> log = new JavacTask(tb, Task.Mode.CMDLINE)
+                .options("-XDrawDiagnostics", "-Werror", "-Xlint:output-file-clash")
+                .outdir(classes)
+                .headerdir(headers)
+                .files(findJavaFiles(src))
+                .run(Task.Expect.FAIL)
+                .writeAll()
+                .getOutputLines(Task.OutputKind.DIRECT);
+
+        // Find expected error line
+        Pattern pattern = Pattern.compile(regex);
+        if (!log.stream().anyMatch(line -> pattern.matcher(line).matches()))
+            throw new Exception("expected error not found: \"" + regex + "\"");
+    }
+
+    public static void main(String... args) throws Exception {
+        new OutputFileClashTest().runTests();
+    }
+}

test/langtools/tools/lib/toolbox/JavacTask.java

@@ -55,6 +55,7 @@ public class JavacTask extends AbstractTask<JavacTask> {
     private List<Path> classpath;
     private List<Path> sourcepath;
     private Path outdir;
+    private Path headerdir;
     private List<String> options;
     private List<String> classes;
     private List<String> files;
@@ -169,6 +170,26 @@ public class JavacTask extends AbstractTask<JavacTask> {
         return this;
     }
 
+    /**
+     * Sets the native header output directory.
+     * @param headerdir the native header output directory
+     * @return this task object
+     */
+    public JavacTask headerdir(String headerdir) {
+        this.headerdir = Paths.get(headerdir);
+        return this;
+    }
+
+    /**
+     * Sets the native header output directory.
+     * @param headerdir the native header output directory
+     * @return this task object
+     */
+    public JavacTask headerdir(Path headerdir) {
+        this.headerdir = headerdir;
+        return this;
+    }
+
     /**
      * Sets the options.
      * @param options the options
@@ -353,6 +374,8 @@ public class JavacTask extends AbstractTask<JavacTask> {
                 fileManager = internalFileManager = compiler.getStandardFileManager(null, null, null);
             if (outdir != null)
                 setLocationFromPaths(StandardLocation.CLASS_OUTPUT, Collections.singletonList(outdir));
+            if (headerdir != null)
+                setLocationFromPaths(StandardLocation.NATIVE_HEADER_OUTPUT, Collections.singletonList(headerdir));
             if (classpath != null)
                 setLocationFromPaths(StandardLocation.CLASS_PATH, classpath);
             if (sourcepath != null)
@@ -422,6 +445,10 @@ public class JavacTask extends AbstractTask<JavacTask> {
             args.add("-d");
             args.add(outdir.toString());
         }
+        if (headerdir != null) {
+            args.add("-h");
+            args.add(headerdir.toString());
+        }
         if (classpath != null) {
             args.add("-classpath");
             args.add(toSearchPath(classpath));