[171808] - Added "suggested parenthesis checker"

codan/org.eclipse.cdt.codan.checkers/.classpath

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/J2SE-1.5"/>
 	<classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
 	<classpathentry kind="src" path="src"/>
 	<classpathentry kind="output" path="bin"/>

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

@@ -52,6 +52,16 @@
             name="Catch uses reference to exception">
       </problem>
       </checker>
-
+      <checker
+            class="org.eclipse.cdt.codan.checkers.sample.SuggestedParenthesisChecker"
+            id="org.eclipse.cdt.codan.checkers.sample.SuggestedParenthesisChecker"
+            name="SuggestedParenthesisChecker">
+      <problem
+            category="org.eclipse.cdt.codan.core.categories.ProgrammingProblems"
+            defaultSeverity="Warning"
+            id="org.eclipse.cdt.codan.checkers.sample.SuggestedParenthesisProblem"
+            name="Suggested parenthesis around expression">
+      </problem>
+      </checker>
    </extension>
 </plugin>

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

@@ -0,0 +1,143 @@
+/*******************************************************************************
+ * 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.ASTNodeProperty;
+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.IASTForStatement;
+import org.eclipse.cdt.core.dom.ast.IASTIfStatement;
+import org.eclipse.cdt.core.dom.ast.IASTTranslationUnit;
+import org.eclipse.cdt.core.dom.ast.IASTUnaryExpression;
+
+/**
+ * This checker finds a problems that cause by lack of understanding operator
+ * precedence in C. In any case it is better to surround expressions in
+ * parenthesis to improve readability. Example: ! x>0 && x<10 (this would be
+ * (!x)>0 && x<10 in C) We only look for &&, || and ! operators (and binary | &
+ * ^ ~)
+ * 
+ * @author Alena
+ * 
+ */
+public class SuggestedParenthesisChecker extends AbstractIndexAstChecker {
+	private static final String ER_ID = "org.eclipse.cdt.codan.checkers.sample.SuggestedParenthesisProblem";
+
+	public void processAst(IASTTranslationUnit ast) {
+		// traverse the ast using the visitor pattern.
+		ast.accept(new ExpressionVisitor());
+	}
+
+	class ExpressionVisitor extends ASTVisitor {
+		private SuspiciousExpressionVisitor svis;
+
+		ExpressionVisitor() {
+			shouldVisitExpressions = true;
+			svis = new SuspiciousExpressionVisitor();
+		}
+
+		public int visit(IASTExpression expression) {
+			int precedence = getPrecedence(expression);
+			if (precedence == 2) { // unary not
+				if (isUsedAsOperand(expression)) {
+					reportProblem(ER_ID, svis.other,
+							"Suggested parenthesis around expression");
+					return PROCESS_SKIP;
+				}
+			}
+			if (precedence >= 0) {
+				synchronized (svis) { // since we use only one instance of this
+										// visitor sync just in case
+					svis.init(expression);
+					expression.accept(svis);
+					if (svis.suspicious == true) {
+						reportProblem(ER_ID, svis.other,
+								"Suggested parenthesis around expression");
+						return PROCESS_SKIP;
+					}
+				}
+			}
+			return PROCESS_CONTINUE;
+		}
+
+		private boolean isUsedAsOperand(IASTExpression expression) {
+			ASTNodeProperty prop = expression.getPropertyInParent();
+			if (prop == IASTBinaryExpression.OPERAND_ONE
+					|| prop == IASTBinaryExpression.OPERAND_TWO
+					|| prop == IASTUnaryExpression.OPERAND)
+				return true;
+			return false;
+		}
+	}
+
+	private int getPrecedence(IASTExpression e) {
+		if (e instanceof IASTBinaryExpression) {
+			IASTBinaryExpression binExpr = (IASTBinaryExpression) e;
+			int operator = binExpr.getOperator();
+			if (operator == IASTBinaryExpression.op_binaryAnd)
+				return 8;
+			if (operator == IASTBinaryExpression.op_binaryXor)
+				return 9;
+			if (operator == IASTBinaryExpression.op_binaryOr)
+				return 10;
+			if (operator == IASTBinaryExpression.op_logicalAnd)
+				return 11;
+			if (operator == IASTBinaryExpression.op_logicalOr)
+				return 12;
+		}
+		if (e instanceof IASTUnaryExpression) {
+			IASTUnaryExpression binExpr = (IASTUnaryExpression) e;
+			int operator = binExpr.getOperator();
+			if (operator == IASTUnaryExpression.op_not)
+				return 2;
+			if (operator == IASTUnaryExpression.op_tilde)
+				return 2;
+		}
+		return -1;
+	}
+
+	class SuspiciousExpressionVisitor extends ASTVisitor {
+		IASTExpression parent;
+		IASTExpression other;
+		boolean suspicious = false;
+
+		void init(IASTExpression e) {
+			parent = e;
+			suspicious = false;
+		}
+
+		SuspiciousExpressionVisitor() {
+			shouldVisitExpressions = true;
+		}
+
+		public int visit(IASTExpression expression) {
+			if (expression == parent)
+				return PROCESS_CONTINUE;
+			if (expression instanceof IASTUnaryExpression) {
+				IASTUnaryExpression uExpr = (IASTUnaryExpression) expression;
+				int operator = uExpr.getOperator();
+				if (operator == IASTUnaryExpression.op_bracketedPrimary) {
+					return PROCESS_SKIP;
+				}
+			}
+			if (getPrecedence(expression) < 0) // not considered operator
+				return PROCESS_CONTINUE;
+			if (getPrecedence(expression) == getPrecedence(parent)) {
+				return PROCESS_SKIP;
+			}
+			suspicious = true;
+			other = expression;
+			return PROCESS_ABORT;
+		}
+	}
+}