--- a/src/jdk.jdeps/share/classes/com/sun/tools/javap/JavapTask.java	Wed Dec 14 17:56:11 2016 -0700
+++ b/src/jdk.jdeps/share/classes/com/sun/tools/javap/JavapTask.java	Wed Dec 14 18:30:56 2016 -0800
@@ -643,9 +643,15 @@
 
         ClassFileInfo cfInfo = read(fo);
         if (!className.endsWith(".class")) {
-            String cfName = cfInfo.cf.getName();
-            if (!cfName.replaceAll("[/$]", ".").equals(className.replaceAll("[/$]", "."))) {
-                reportWarning("warn.unexpected.class", className, cfName.replace('/', '.'));
+            if (cfInfo.cf.this_class == 0) {
+                if (!className.equals("module-info")) {
+                    reportWarning("warn.unexpected.class", fo.getName(), className);
+                }
+            } else {
+                String cfName = cfInfo.cf.getName();
+                if (!cfName.replaceAll("[/$]", ".").equals(className.replaceAll("[/$]", "."))) {
+                    reportWarning("warn.unexpected.class", fo.getName(), className);
+                }
             }
         }
         write(cfInfo);

--- a/src/jdk.jdeps/share/classes/com/sun/tools/javap/resources/javap.properties	Wed Dec 14 17:56:11 2016 -0700
+++ b/src/jdk.jdeps/share/classes/com/sun/tools/javap/resources/javap.properties	Wed Dec 14 18:30:56 2016 -0800
@@ -27,7 +27,7 @@
 use -help for a list of possible options
 
 warn.prefix=Warning:
-warn.unexpected.class=Binary file {0} contains {1}
+warn.unexpected.class=File {0} does not contain class {1}
 
 note.prefix=Note:
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javap/TestClassNameWarning.java	Wed Dec 14 18:30:56 2016 -0800
@@ -0,0 +1,241 @@
+/*
+ * Copyright (c) 2016, 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 8170708
+ * @summary javap -m <module> cannot read a module-info.class
+ * @library /tools/lib
+ * @modules
+ *      jdk.compiler/com.sun.tools.javac.api
+ *      jdk.compiler/com.sun.tools.javac.main
+ *      jdk.jdeps/com.sun.tools.classfile
+ *      jdk.jdeps/com.sun.tools.javap
+ * @build toolbox.JavacTask toolbox.JavapTask toolbox.ToolBox toolbox.TestRunner
+ * @run main TestClassNameWarning
+ */
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.List;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+import com.sun.tools.classfile.ClassFile;
+import com.sun.tools.classfile.ClassWriter;
+
+import toolbox.JavacTask;
+import toolbox.JavapTask;
+import toolbox.Task;
+import toolbox.TestRunner;
+import toolbox.ToolBox;
+
+public class TestClassNameWarning extends TestRunner {
+    public static void main(String... args) throws Exception {
+        new TestClassNameWarning().runTests(m -> new Object[] { Paths.get(m.getName()) });
+    }
+
+    private ToolBox tb = new ToolBox();
+
+    TestClassNameWarning() {
+        super(System.err);
+    }
+
+    /**
+     * Baseline test for normal classes.
+     */
+    @Test
+    public void testStandardClass(Path base) throws Exception {
+        Path src = base.resolve("src");
+        Path classes = Files.createDirectories(base.resolve("classes"));
+        tb.writeJavaFiles(src, "class A { }");
+
+        new JavacTask(tb)
+                .outdir(classes.toString())
+                .files(tb.findJavaFiles(src))
+                .run()
+                .writeAll();
+
+        List<String> log = new JavapTask(tb)
+                .classpath(classes.toString())
+                .classes("A")
+                .run()
+                .writeAll()
+                .getOutputLines(Task.OutputKind.DIRECT);
+
+        checkOutput(log, false, "^(Warning|Error)");
+        checkOutput(log, true, "class A");
+    }
+
+    /**
+     * Test that module-info can be used to name the .class file
+     * for a module declaration (i.e. ACC_MODULE, this_class == 0)
+     * This is the primary test case for the bug as reported.
+     */
+    @Test
+    public void testStandardModuleInfo(Path base) throws Exception {
+        Path src = base.resolve("src");
+        Path classes = Files.createDirectories(base.resolve("classes"));
+        tb.writeJavaFiles(src, "module m { }");
+
+        new JavacTask(tb)
+                .outdir(classes.toString())
+                .files(tb.findJavaFiles(src))
+                .run()
+                .writeAll();
+
+        List<String> log = new JavapTask(tb)
+                .options("--module-path", classes.toString(),
+                        "--module", "m")
+                .classes("module-info")
+                .run()
+                .writeAll()
+                .getOutputLines(Task.OutputKind.DIRECT);
+
+        checkOutput(log, false, "^(Warning|Error)");
+        checkOutput(log, true, "module m");
+    }
+
+    /**
+     * Test module-info can still be used to find a weirdly named
+     * class equivalent to "class module-info { }" if that were legal in JLS.
+     * Such a class file would arguably be legal in certain selected contexts.
+     */
+    @Test
+    public void testLegacyModuleInfo(Path base) throws Exception {
+        Path src = base.resolve("src");
+        Path classes = Files.createDirectories(base.resolve("classes"));
+        tb.writeJavaFiles(src, "class module_info { }");
+
+        new JavacTask(tb)
+                .outdir(classes.toString())
+                .files(tb.findJavaFiles(src))
+                .run()
+                .writeAll();
+
+        byte[] bytes = Files.readAllBytes(classes.resolve("module_info.class"));
+        byte[] searchBytes = "module_info".getBytes("UTF-8");
+        byte[] replaceBytes = "module-info".getBytes("UTF-8");
+        for (int i = 0; i < bytes.length - searchBytes.length; i++) {
+            if (Arrays.equals(bytes, i, i + searchBytes.length,
+                                searchBytes, 0, searchBytes.length)) {
+                System.arraycopy(replaceBytes, 0, bytes, i, replaceBytes.length);
+            }
+        }
+        Files.write(classes.resolve("module-info.class"), bytes);
+
+        List<String> log = new JavapTask(tb)
+                .classpath(classes.toString())
+                .options("-bootclasspath", "") // hide all system classes
+                .classes("module-info")
+                .run()
+                .writeAll()
+                .getOutputLines(Task.OutputKind.DIRECT);
+
+        checkOutput(log, false, "^(Warning|Error)");
+        checkOutput(log, true, "class module-info");
+    }
+
+    /**
+     * Test an invalid class, with this_class == 0.
+     */
+    @Test
+    public void testNoNameClass(Path base) throws Exception {
+        Path src = base.resolve("src");
+        Path classes = Files.createDirectories(base.resolve("classes"));
+        tb.writeJavaFiles(src, "class A { }");
+
+        new JavacTask(tb)
+                .outdir(classes.toString())
+                .files(tb.findJavaFiles(src))
+                .run()
+                .writeAll();
+
+        ClassFile cf = ClassFile.read(classes.resolve("A.class"));
+        ClassFile cf2 = new ClassFile(
+                cf.magic, cf.minor_version, cf.major_version, cf.constant_pool,
+                cf.access_flags,
+                0, // this_class,
+                cf.super_class, cf.interfaces, cf.fields, cf.methods, cf.attributes);
+        new ClassWriter().write(cf2, Files.newOutputStream(classes.resolve("Z.class")));
+
+        List<String> log = new JavapTask(tb)
+                .classpath(classes.toString())
+                .classes("Z")
+                .run()
+                .writeAll()
+                .getOutputLines(Task.OutputKind.DIRECT);
+
+        checkOutput(log, true, "Warning:.*Z.class does not contain class Z");
+    }
+
+    /**
+     * Test a class with unexpected contents.
+     * This is the arguably the most common negative case.
+     */
+    @Test
+    public void testWrongNameClass(Path base) throws Exception {
+        Path src = base.resolve("src");
+        Path classes = Files.createDirectories(base.resolve("classes"));
+        tb.writeJavaFiles(src, "class A { }");
+
+        new JavacTask(tb)
+                .outdir(classes.toString())
+                .files(tb.findJavaFiles(src))
+                .run()
+                .writeAll();
+
+        Files.move(classes.resolve("A.class"), classes.resolve("B.class"));
+
+        List<String> log = new JavapTask(tb)
+                .classpath(classes.toString())
+                .classes("B")
+                .run()
+                .writeAll()
+                .getOutputLines(Task.OutputKind.DIRECT);
+
+        checkOutput(log, true, "Warning:.*B.class does not contain class B");
+    }
+
+    /**
+     * Check that the output does, or does not, contain lines matching a regex.
+     */
+    private void checkOutput(List<String> log, boolean expect, String regex) {
+        Pattern p = Pattern.compile(regex);
+        List<String> matches = log.stream()
+                .filter(line -> p.matcher(line).find())
+                .collect(Collectors.toList());
+        if (expect) {
+            if (matches.isEmpty()) {
+                error("expected output not found: " + regex);
+            }
+        } else {
+            if (!matches.isEmpty()) {
+                error("unexpected output found: " + matches);
+            }
+        }
+    }
+}
+