--- a/src/share/classes/com/sun/tools/javac/processing/JavacMessager.java	Thu Apr 26 14:07:29 2012 -0700
+++ b/src/share/classes/com/sun/tools/javac/processing/JavacMessager.java	Fri May 04 07:55:51 2012 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2012, 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
@@ -99,6 +99,7 @@
         if (treeTop != null) {
             newSource = treeTop.snd.sourcefile;
             if (newSource != null) {
+                // save the old version and reinstate it later
                 oldSource = log.useSource(newSource);
                 pos = treeTop.fst.pos();
             }
@@ -131,7 +132,8 @@
                 break;
             }
         } finally {
-            if (oldSource != null)
+            // reinstate the saved version, only if it was saved earlier
+            if (newSource != null)
                 log.useSource(oldSource);
         }
     }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/tools/javac/processing/messager/MessagerDiags.java	Fri May 04 07:55:51 2012 -0700
@@ -0,0 +1,131 @@
+/*
+ * Copyright (c) 2012, 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 7166010
+ * @summary  warnings printed by annotation processors uses incorrect source
+ */
+import com.sun.source.util.JavacTask;
+import java.io.IOException;
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Set;
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.Messager;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedAnnotationTypes;
+import javax.annotation.processing.SupportedSourceVersion;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.TypeElement;
+import javax.tools.Diagnostic;
+import javax.tools.DiagnosticCollector;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.SimpleJavaFileObject;
+import javax.tools.ToolProvider;
+
+import static javax.tools.Diagnostic.Kind.*;
+import static javax.tools.JavaFileObject.Kind.*;
+
+@SupportedSourceVersion(SourceVersion.RELEASE_6)
+@SupportedAnnotationTypes("*")
+public class MessagerDiags extends AbstractProcessor {
+    static final String CNAME = "Test";
+    static final String TEST_JAVA = CNAME + ".java";
+    static final String TEST_JAVA_URI_NAME = "myfo:/" + TEST_JAVA;
+    static final String WRN_NO_SOURCE   = "warning without source";
+    static final String WRN_WITH_SOURCE = "warning with source";
+    static final String NONE = "<none>";
+    static final String[] EXPECTED = { NONE + ":-1--1:" + WRN_NO_SOURCE,
+                                       TEST_JAVA + ":0-13:" + WRN_WITH_SOURCE,
+                                       NONE + ":-1--1:" + WRN_NO_SOURCE
+    };
+
+    @Override
+    public boolean process(Set<? extends TypeElement> annotations,
+                           RoundEnvironment roundEnv) {
+        Messager messager = processingEnv.getMessager();
+        for (Element e : roundEnv.getRootElements()) {
+            messager.printMessage(WARNING, WRN_NO_SOURCE);
+            messager.printMessage(WARNING, WRN_WITH_SOURCE, e);
+            messager.printMessage(WARNING, WRN_NO_SOURCE);
+        }
+        return false;
+    }
+
+    public static void main(String... args) throws IOException {
+        final String bootPath = System.getProperty("sun.boot.class.path");
+        final JavaCompiler tool = ToolProvider.getSystemJavaCompiler();
+        assert tool != null;
+
+        DiagnosticCollector<JavaFileObject> dc = new DiagnosticCollector<>();
+        List<String> options = new LinkedList<>();
+        options.addAll(Arrays.asList("-bootclasspath",  bootPath,
+                        "-source", "1.6", "-classpath",
+                        System.getProperty("java.class.path")));
+        options.addAll(Arrays.asList("-processor",
+                       MessagerDiags.class.getName()));
+        JavacTask ct = (JavacTask)tool.getTask(null, null, dc, options, null,
+                        Arrays.asList(new MyFileObject("class " + CNAME + " {}")));
+        ct.analyze();
+
+        List<String> obtainedErrors = new ArrayList<>();
+
+        for (Diagnostic<? extends JavaFileObject> d : dc.getDiagnostics()) {
+            String dSource;
+            if (d.getSource() != null) {
+                dSource = d.getSource().toUri().getPath();
+                dSource = dSource.substring(dSource.lastIndexOf('/') + 1);
+            } else {
+                dSource = NONE;
+            }
+            obtainedErrors.add(dSource + ":" + d.getStartPosition() + "-" +
+                    d.getEndPosition() + ":" + d.getMessage(null));
+        }
+        List<String> expectedErrors = Arrays.asList(EXPECTED);
+        if (!expectedErrors.equals(obtainedErrors)) {
+            System.err.println("Expected: " + expectedErrors);
+            System.err.println("Obtained: " + obtainedErrors);
+            throw new AssertionError("Messages don't match");
+        }
+    }
+
+    static class MyFileObject extends SimpleJavaFileObject {
+        private String text;
+        public MyFileObject(String text) {
+            super(URI.create(TEST_JAVA_URI_NAME), SOURCE);
+            this.text = text;
+        }
+        @Override
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+            return text;
+        }
+    }
+}