[Fb-contrib-commit] SF.net SVN: fb-contrib:[1153] trunk/fb-contrib

[<dbr...@us...>]

Revision: 1153
          http://fb-contrib.svn.sourceforge.net/fb-contrib/?rev=1153&view=rev
Author:   dbrosius
Date:     2009-04-11 02:50:18 +0000 (Sat, 11 Apr 2009)

Log Message:
-----------
new UNNC detector

Modified Paths:
--------------
    trunk/fb-contrib/etc/findbugs.xml
    trunk/fb-contrib/etc/messages.xml

Added Paths:
-----------
    trunk/fb-contrib/samples/UNNC_Sample.java
    trunk/fb-contrib/src/com/mebigfatguy/fbcontrib/detect/UnnecessaryNewNullCheck.java

Modified: trunk/fb-contrib/etc/findbugs.xml
===================================================================
--- trunk/fb-contrib/etc/findbugs.xml	2009-04-10 15:44:00 UTC (rev 1152)
+++ trunk/fb-contrib/etc/findbugs.xml	2009-04-11 02:50:18 UTC (rev 1153)
@@ -336,6 +336,10 @@
 			speed="moderate"
 			reports="BED_BOGUS_EXCEPTION_DECLARATION" />
 			
+	<Detector class="com.mebigfatguy.fbcontrib.detect.UnnecessaryNewNullCheck"
+			speed="fast"
+			reports="UNNC_UNNECESSARY_NEW_NULL_CHECK" />
+			
    	<!-- BugPattern -->
 	
 	<BugPattern abbrev="ISB" type="ISB_INEFFICIENT_STRING_BUFFERING" category="PERFORMANCE" />
@@ -452,4 +456,5 @@
 	<BugPattern abbrev="IICU" type="IICU_INCORRECT_INTERNAL_CLASS_USE" category="CORRECTNESS" />
 	<BugPattern abbrev="DSOC" type="DSOC_DUBIOUS_SET_OF_COLLECTIONS" category="PERFORMANCE" />
 	<BugPattern abbrev="BED" type="BED_BOGUS_EXCEPTION_DECLARATION" category="CORRECTNESS" experimental="true" />
+	<BugPattern abbrev="UNNC" type="UNNC_UNNECESSARY_NEW_NULL_CHECK" category="CORRECTNESS" experimental="true" />
 </FindbugsPlugin>
\ No newline at end of file

Modified: trunk/fb-contrib/etc/messages.xml
===================================================================
--- trunk/fb-contrib/etc/messages.xml	2009-04-10 15:44:00 UTC (rev 1152)
+++ trunk/fb-contrib/etc/messages.xml	2009-04-11 02:50:18 UTC (rev 1153)
@@ -935,6 +935,18 @@
 		</Details>
 	</Detector>
 	
+	<Detector class="com.mebigfatguy.fbcontrib.detect.UnnecessaryNewNullCheck">
+		<Details>
+			<![CDATA[
+			<p>looks for allocations of objects, and then immediately checking to see if the
+			object is null, or non null. As the new operator is guaranteed to eiher succeed, or throw
+			an exception, this null check is useless, and denotes a misunderstanding as to how
+			the jvm works. You can remove this guard.</p>
+			<p>It is a fast detector</p>
+			]]>
+		</Details>
+	</Detector>
+
 	<!-- BugPattern -->	
 	                
 	<BugPattern type="ISB_INEFFICIENT_STRING_BUFFERING">
@@ -2444,6 +2456,18 @@
 		</Details>
 	</BugPattern>
 	
+	<BugPattern type="UNNC_UNNECESSARY_NEW_NULL_CHECK">
+		<ShortDescription>method checks the result of a new allocation</ShortDescription>
+		<LongDescription>method {1} checks the result of a new allocation</LongDescription>
+		<Details>
+			<![CDATA[
+			<p>This method allocations an object with new, and then checks that the object is null
+			or non null. As the new operator is guaranteed to either succeed or throw an exception,
+			this null check is unnecessary and can be removed.
+			]]>
+		</Details>
+	</BugPattern>
+	
 	<!-- BugCode -->
 	
 	<BugCode abbrev="ISB">Inefficient String Buffering</BugCode>
@@ -2522,4 +2546,5 @@
 	<BugCode abbrev="IICU">Incorrect Internal Class use</BugCode>
 	<BugCode abbrev="DSOC">Dubious Set of Collections</BugCode>
 	<BugCode abbrev="BED">Bogus Exception Declaration</BugCode>
+	<BugCode abbrev="UNNC">Unnecessary New Null Check</BugCode>
 </MessageCollection>
\ No newline at end of file

Added: trunk/fb-contrib/samples/UNNC_Sample.java
===================================================================
--- trunk/fb-contrib/samples/UNNC_Sample.java	                        (rev 0)
+++ trunk/fb-contrib/samples/UNNC_Sample.java	2009-04-11 02:50:18 UTC (rev 1153)
@@ -0,0 +1,55 @@
+
+
+public class UNNC_Sample {
+	public void testPosNEW()
+	{
+		UNNC_Sample sample = new UNNC_Sample();
+		
+		if (sample != null)
+			System.out.println("OK");
+	}
+	
+	public void testNegNEW()
+	{
+		UNNC_Sample sample = new UNNC_Sample();
+		
+		if (sample == null)
+			return;
+		
+		System.out.println("OK");
+	}
+	
+	public void testPosANEWARAY()
+	{
+		String[] s = new String[10];
+		if (s != null)
+			System.out.println("OK");
+	}
+	
+	public void testNegANEWARRAY()
+	{
+		String[] s = new String[10];
+		if (s == null)
+			return;
+		
+		System.out.println("OK");
+	}
+	
+	public void testPosMULTIANEWARRAY()
+	{
+		String[][] s = new String[10][5];
+		if (s != null)
+			System.out.println("OK");
+	}
+	
+	public void testNegMULTIANEWARRAY()
+	{
+		String[][] s = new String[10][5];
+		if (s == null)
+			return;
+		
+		System.out.println("OK");
+	}
+	
+	
+}


Property changes on: trunk/fb-contrib/samples/UNNC_Sample.java
___________________________________________________________________
Added: svn:mime-type
   + text/plain
Added: svn:eol-style
   + native

Added: trunk/fb-contrib/src/com/mebigfatguy/fbcontrib/detect/UnnecessaryNewNullCheck.java
===================================================================
--- trunk/fb-contrib/src/com/mebigfatguy/fbcontrib/detect/UnnecessaryNewNullCheck.java	                        (rev 0)
+++ trunk/fb-contrib/src/com/mebigfatguy/fbcontrib/detect/UnnecessaryNewNullCheck.java	2009-04-11 02:50:18 UTC (rev 1153)
@@ -0,0 +1,140 @@
+package com.mebigfatguy.fbcontrib.detect;
+
+import java.util.BitSet;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.apache.bcel.Constants;
+import org.apache.bcel.classfile.Code;
+import org.apache.bcel.classfile.CodeException;
+
+import com.mebigfatguy.fbcontrib.utils.Integer14;
+import com.mebigfatguy.fbcontrib.utils.RegisterUtils;
+
+import edu.umd.cs.findbugs.BugInstance;
+import edu.umd.cs.findbugs.BugReporter;
+import edu.umd.cs.findbugs.BytecodeScanningDetector;
+import edu.umd.cs.findbugs.OpcodeStack;
+import edu.umd.cs.findbugs.ba.ClassContext;
+
+/** looks for construction of new objects, and then the immediate testing
+ * whether the object is null or not. As the new operator will always succeed,
+ * or through an exception, this test is unnecessary and represents a misunderstanding
+ * as to how the jvm works.
+ */
+public class UnnecessaryNewNullCheck extends BytecodeScanningDetector 
+{
+	private final BugReporter bugReporter;
+	private OpcodeStack stack;
+	private Set<Integer> allocationRegs;
+	private Set<Integer> handlerStarts;
+	
+	public UnnecessaryNewNullCheck(BugReporter bugReporter) {
+		this.bugReporter = bugReporter;
+	}
+	
+	@Override
+	public void visitClassContext(ClassContext classContext) {
+		try {
+			stack = new OpcodeStack();
+			allocationRegs = new HashSet<Integer>();
+			handlerStarts = new HashSet<Integer>();
+			super.visitClassContext(classContext);
+		} finally {
+			stack = null;
+			allocationRegs = null;
+			handlerStarts = null;
+		}
+	}
+	
+	@Override
+	public void visitCode(Code obj) {
+		if (prescreen()) {
+			stack.resetForMethodEntry(this);
+			allocationRegs.clear();
+			handlerStarts.clear();
+			
+			CodeException[] ce = obj.getExceptionTable();
+			if (ce != null) {
+				for (CodeException element : ce) {
+					handlerStarts.add(Integer14.valueOf(element.getHandlerPC()));
+				}
+			}
+			super.visitCode(obj);
+		}
+	}
+	
+	@Override
+	public void sawOpcode(int seen) {
+		boolean sawAlloc = false;
+		try {
+			switch (seen) {
+				case NEW:
+				case ANEWARRAY:
+				case MULTIANEWARRAY:
+					sawAlloc = true;
+				break;
+				
+				case ASTORE:
+				case ASTORE_0:
+				case ASTORE_1:
+				case ASTORE_2:
+				case ASTORE_3:
+					if (stack.getStackDepth() > 0) {
+						OpcodeStack.Item item = stack.getStackItem(0);
+						int reg = RegisterUtils.getAStoreReg(this, seen);
+						if (item.getUserValue() != null) {
+							allocationRegs.add(Integer14.valueOf(reg));
+						} else {
+							allocationRegs.remove(Integer14.valueOf(reg));
+						}
+					}
+				break;
+				
+				case ALOAD:
+				case ALOAD_0:
+				case ALOAD_1:
+				case ALOAD_2:
+				case ALOAD_3:
+					int reg = RegisterUtils.getALoadReg(this, seen);
+					if (allocationRegs.contains(Integer14.valueOf(reg))) {
+						sawAlloc = true;
+					}
+				break;
+				
+				case IFNONNULL:
+				case IFNULL:
+					if (stack.getStackDepth() > 0) {
+						OpcodeStack.Item item = stack.getStackItem(0);
+						if (item.getUserValue() != null) {
+							bugReporter.reportBug(new BugInstance(this, "UNNC_UNNECESSARY_NEW_NULL_CHECK", NORMAL_PRIORITY)
+									   .addClass(this)
+									   .addMethod(this)
+									   .addSourceLine(this));
+						}
+					}
+				break;
+			}
+			
+			if (handlerStarts.contains(Integer14.valueOf(getPC())))
+				allocationRegs.clear();
+					
+		} finally {
+			stack.sawOpcode(this, seen);
+			if (sawAlloc) {
+				if (stack.getStackDepth() > 0) {
+					OpcodeStack.Item item = stack.getStackItem(0);
+					item.setUserValue(Boolean.TRUE);
+				}
+			}
+		}
+	}
+	
+	private boolean prescreen() {
+		BitSet bytecodeSet = getClassContext().getBytecodeSet(getMethod());
+		return (bytecodeSet != null) && 
+		       (bytecodeSet.get(Constants.NEW) 
+		  	 || bytecodeSet.get(Constants.ANEWARRAY)
+			 || bytecodeSet.get(Constants.MULTIANEWARRAY));
+	}
+}


Property changes on: trunk/fb-contrib/src/com/mebigfatguy/fbcontrib/detect/UnnecessaryNewNullCheck.java
___________________________________________________________________
Added: svn:mime-type
   + text/plain
Added: svn:eol-style
   + native


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