Add models of FileChannel.tryLock methods.

Summary: Add models of the java.nio.channels.FileChannel.tryLock methods which can
return null according to the java docs.

public

Reviewed By: sblackshear, cristianoc

Differential Revision: D2650050

fb-gh-sync-id: ae6c8ce

infer/models/java/src/java/nio/channels/FileChannel.java

@@ -9,7 +9,8 @@
 
 package java.nio.channels;
 
-import com.facebook.infer.models.InferBuiltins;
+import com.facebook.infer.models.InferUndefined;
+import javax.annotation.Nullable;
 import java.nio.channels.spi.AbstractInterruptibleChannel;
 import java.nio.channels.FileLock;
 
@@ -26,6 +27,16 @@ public abstract class FileChannel extends AbstractInterruptibleChannel {
         private String displayName;
     }
 
-    private native FileLock getFileLock();
+    public @Nullable FileLock tryLock() {
+        if (InferUndefined.boolean_undefined()) {
+            return null;
+        } else {
+            return (FileLock)InferUndefined.object_undefined();
+        }
+    }
+
+    public final @Nullable FileLock tryLock(long position, long size, boolean shared) {
+        return tryLock();
+    }
 
 }

infer/tests/ant_report.json

@@ -359,6 +359,11 @@
     "file": "codetoanalyze/java/infer/NullPointerExceptions.java",
     "bug_type": "NULL_DEREFERENCE"
   },
+  {
+    "procedure": "String NullPointerExceptions.nullTryLock(FileChannel)",
+    "file": "codetoanalyze/java/infer/NullPointerExceptions.java",
+    "bug_type": "NULL_DEREFERENCE"
+  },
   {
     "procedure": "void ReaderLeaks.readerNotClosedAfterRead()",
     "file": "codetoanalyze/java/infer/ReaderLeaks.java",

infer/tests/buck_report.json

@@ -559,6 +559,11 @@
     "file": "infer/tests/codetoanalyze/java/infer/NullPointerExceptions.java",
     "bug_type": "NULL_DEREFERENCE"
   },
+  {
+    "procedure": "String NullPointerExceptions.nullTryLock(FileChannel)",
+    "file": "infer/tests/codetoanalyze/java/infer/NullPointerExceptions.java",
+    "bug_type": "NULL_DEREFERENCE"
+  },
   {
     "procedure": "void ContextLeaks.directLeak()",
     "file": "infer/tests/codetoanalyze/java/infer/ContextLeaks.java",

infer/tests/codetoanalyze/java/infer/NullPointerExceptions.java

@@ -24,6 +24,8 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileLock;
 import java.lang.System;
 import java.util.HashMap;
 
@@ -452,4 +454,9 @@ public class NullPointerExceptions {
     o.toString();
   }
 
+  String nullTryLock(FileChannel chan) throws IOException {
+    FileLock lock = chan.tryLock();
+    return lock.toString(); // expect possible NullPointerException as lock == null is possible
+  }
+
 }

infer/tests/endtoend/java/infer/NullPointerExceptionTest.java

@@ -65,7 +65,8 @@ public class NullPointerExceptionTest {
         "testSystemGetPropertyArgument",
         "testSystemGetPropertyReturn",
         "derefNull",
-        "nullListFiles"
+        "nullListFiles",
+        "nullTryLock"
     };
     assertThat(
         "Results should contain " + NULL_DEREFERENCE,