added statement has no effect checker

codan/org.eclipse.cdt.codan.checkers/plugin.xml

@@ -14,6 +14,19 @@
             id="org.eclipse.cdt.codan.checkers.sample.AssignmentInConditionProblem"
             name="Assignment in condition">
       </problem>
+      
+      
+      </checker>
+            <checker
+            class="org.eclipse.cdt.codan.checkers.sample.StatementHasNoEffectChecker"
+            id="org.eclipse.cdt.codan.checkers.sample.StatementHasNoEffectChecker"
+            name="StatementHasNoEffectChecker">
+      <problem
+            category="org.eclipse.cdt.codan.core.categories.ProgrammingProblems"
+            defaultSeverity="Warning"
+            id="org.eclipse.cdt.codan.checkers.sample.StatementHasNoEffectProblem"
+            name="Statement has no effect">
+      </problem>
       </checker>
    </extension>
 </plugin>

codan/org.eclipse.cdt.codan.checkers/src/org/eclipse/cdt/codan/checkers/sample/StatementHasNoEffectChecker.java

@@ -0,0 +1,86 @@
+/*******************************************************************************
+ * Copyright (c) 2009 Alena Laskavaia 
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *    Alena Laskavaia  - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.cdt.codan.checkers.sample;
+
+import org.eclipse.cdt.codan.core.model.AbstractIndexAstChecker;
+import org.eclipse.cdt.core.dom.ast.ASTVisitor;
+import org.eclipse.cdt.core.dom.ast.IASTBinaryExpression;
+import org.eclipse.cdt.core.dom.ast.IASTExpression;
+import org.eclipse.cdt.core.dom.ast.IASTExpressionStatement;
+import org.eclipse.cdt.core.dom.ast.IASTStatement;
+import org.eclipse.cdt.core.dom.ast.IASTTranslationUnit;
+import org.eclipse.cdt.core.dom.ast.IASTUnaryExpression;
+
+/**
+ * Checker that detects statements without effect such as
+ * 
+ * a+b;
+ * 
+ * or
+ * 
+ * +b;
+ * 
+ * 
+ */
+public class StatementHasNoEffectChecker extends AbstractIndexAstChecker {
+	private static final String ER_ID = "org.eclipse.cdt.codan.checkers.sample.StatementHasNoEffectProblem";
+
+	@Override
+	public void processAst(IASTTranslationUnit ast) {
+		// traverse the ast using the visitor pattern.
+		ast.accept(new CheckStmpVisitor());
+	}
+
+	class CheckStmpVisitor extends ASTVisitor {
+		CheckStmpVisitor() {
+			shouldVisitStatements = true;
+		}
+
+		public int visit(IASTStatement stmt) {
+			if (stmt instanceof IASTExpressionStatement) {
+				if (hasNoEffect(((IASTExpressionStatement) stmt)
+						.getExpression())) {
+					reportProblem(ER_ID, getFile(), stmt.getFileLocation()
+							.getStartingLineNumber(), "Statement has no effect");
+				}
+				return PROCESS_SKIP;
+			}
+			return PROCESS_CONTINUE;
+		}
+
+		/**
+		 * We consider has not effect binary statements without assignment and
+		 * unary statement which is not dec and inc
+		 * 
+		 * @param e
+		 * @return
+		 */
+		private boolean hasNoEffect(IASTExpression e) {
+			if (e instanceof IASTBinaryExpression) {
+				IASTBinaryExpression binExpr = (IASTBinaryExpression) e;
+				return binExpr.getOperator() != IASTBinaryExpression.op_assign;
+			}
+			if (e instanceof IASTUnaryExpression) {
+				IASTUnaryExpression unaryExpr = (IASTUnaryExpression) e;
+				int operator = unaryExpr.getOperator();
+				switch (operator) {
+				case IASTUnaryExpression.op_postFixDecr:
+				case IASTUnaryExpression.op_prefixDecr:
+				case IASTUnaryExpression.op_postFixIncr:
+				case IASTUnaryExpression.op_prefixIncr:
+					return false;
+				}
+				return true;
+			}
+			return false;
+		}
+	}
+}