Implement #191

analysis/config.d

@@ -56,4 +56,7 @@ struct StaticAnalysisConfig
 
 	@INI("Checks that opEquals and toHash are both defined or neither are defined")
 	bool opequals_tohash_check;
+
+	@INI("Checks for subtraction from .length properties")
+	bool length_subtraction_check;
 }

analysis/length_subtraction.d

@@ -0,0 +1,73 @@
+//          Copyright Brian Schott (Sir Alaran) 2014.
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          http://www.boost.org/LICENSE_1_0.txt)
+
+module analysis.length_subtraction;
+
+import std.stdio;
+
+import std.d.ast;
+import std.d.lexer;
+import analysis.base;
+import analysis.helpers;
+
+
+/**
+ * Checks for subtraction from a .length property. This is usually a bug.
+ */
+class LengthSubtractionCheck : BaseAnalyzer
+{
+	alias visit = BaseAnalyzer.visit;
+
+	this(string fileName)
+	{
+		super(fileName);
+	}
+
+	override void visit(const AddExpression addExpression)
+	{
+		if (addExpression.operator == tok!"-")
+		{
+			UnaryExpression l = cast(UnaryExpression) addExpression.left;
+			UnaryExpression r = cast(UnaryExpression) addExpression.right;
+			if (l is null || r is null)
+			{
+//				stderr.writeln(__FILE__, " ", __LINE__);
+				goto end;
+			}
+			if (r.primaryExpression is null || r.primaryExpression.primary.type != tok!"intLiteral")
+			{
+//				stderr.writeln(__FILE__, " ", __LINE__);
+				goto end;
+			}
+			if (l.identifierOrTemplateInstance is null
+				|| l.identifierOrTemplateInstance.identifier.text != "length")
+			{
+//				stderr.writeln(__FILE__, " ", __LINE__);
+				goto end;
+			}
+			const(Token) token = l.identifierOrTemplateInstance.identifier;
+			addErrorMessage(token.line, token.column,
+				"Avoid subtracting from '.length' as it may be unsigned.");
+		}
+	end:
+		addExpression.accept(this);
+	}
+}
+
+unittest
+{
+	import analysis.config;
+	StaticAnalysisConfig sac;
+	sac.if_else_same_check = true;
+	assertAnalyzerWarnings(q{
+		void testSizeT()
+		{
+			if (i < a.length - 1) // [warn]: Avoid subtracting from '.length' as it may be unsigned.
+				writeln("something");
+		}
+	}c, sac);
+	stderr.writeln("Unittest for IfElseSameCheck passed.");
+}
+

analysis/run.d

@@ -25,6 +25,7 @@ import analysis.constructors;
 import analysis.unused;
 import analysis.duplicate_attribute;
 import analysis.opequals_without_tohash;
+import analysis.length_subtraction;
 
 void messageFunction(string fileName, size_t line, size_t column, string message,
 	bool isError)
@@ -94,6 +95,7 @@ string[] analyze(string fileName, ubyte[] code, StaticAnalysisConfig analysisCon
 	if (analysisConfig.unused_variable_check) checks ~= new UnusedVariableCheck(fileName);
 	if (analysisConfig.duplicate_attribute) checks ~= new DuplicateAttributeCheck(fileName);
 	if (analysisConfig.opequals_tohash_check) checks ~= new OpEqualsWithoutToHashCheck(fileName);
+	if (analysisConfig.length_subtraction_check) checks ~= new LengthSubtractionCheck(fileName);
 
 	foreach (check; checks)
 	{

astprinter.d

@@ -61,12 +61,12 @@ class XMLPrinter : ASTVisitor
 	{
 		output.writeln("<andAndExpression>");
 		output.writeln("<left>");
-		andAndExpression.left.accept(this);
+		visit(andAndExpression.left);
 		output.writeln("</left>");
 		if (andAndExpression.right !is null)
 		{
 			output.writeln("<right>");
-			andAndExpression.right.accept(this);
+			visit(andAndExpression.right);
 			output.writeln("</right>");
 		}
 		output.writeln("</andAndExpression>");
@@ -76,12 +76,12 @@ class XMLPrinter : ASTVisitor
 	{
 		output.writeln("<andExpression>");
 		output.writeln("<left>");
-		andExpression.left.accept(this);
+		visit(andExpression.left);
 		output.writeln("</left>");
 		if (andExpression.right !is null)
 		{
 			output.writeln("<right>");
-			andExpression.right.accept(this);
+			visit(andExpression.right);
 			output.writeln("</right>");
 		}
 		output.writeln("</andExpression>");
@@ -441,10 +441,10 @@ class XMLPrinter : ASTVisitor
 	{
 		output.writeln("<equalExpression operator=\"", str(equalExpression.operator), "\">");
 		output.writeln("<left>");
-		equalExpression.left.accept(this);
+		visit(equalExpression.left);
 		output.writeln("</left>");
 		output.writeln("<right>");
-		equalExpression.right.accept(this);
+		visit(equalExpression.right);
 		output.writeln("</right>");
 		output.writeln("</equalExpression>");
 	}
@@ -956,12 +956,12 @@ class XMLPrinter : ASTVisitor
 	{
 		output.writeln("<powExpression>");
 		output.writeln("<left>");
-		powExpression.left.accept(this);
+		visit(powExpression.left);
 		output.writeln("</left>");
 		if (powExpression.right !is null)
 		{
 			output.writeln("<right>");
-			powExpression.right.accept(this);
+			visit(powExpression.right);
 			output.writeln("</right>");
 		}
 		output.writeln("</powExpression>");
@@ -997,10 +997,10 @@ class XMLPrinter : ASTVisitor
 		output.writeln("<relExpression operator=\"",
 			xmlAttributeEscape(str(relExpression.operator)), "\">");
 		output.writeln("<left>");
-		relExpression.left.accept(this);
+		visit(relExpression.left);
 		output.writeln("</left>");
 		output.writeln("<right>");
-		relExpression.right.accept(this);
+		visit(relExpression.right);
 		output.writeln("</right>");
 		output.writeln("</relExpression>");
 	}
@@ -1037,10 +1037,10 @@ class XMLPrinter : ASTVisitor
 		output.writeln("<shiftExpression operator=\"",
 			xmlAttributeEscape(str(shiftExpression.operator)), "\">");
 		output.writeln("<left>");
-		shiftExpression.left.accept(this);
+		visit(shiftExpression.left);
 		output.writeln("</left>");
 		output.writeln("<right>");
-		shiftExpression.right.accept(this);
+		visit(shiftExpression.right);
 		output.writeln("</right>");
 		output.writeln("</shiftExpression>");
 	}
@@ -1496,12 +1496,12 @@ class XMLPrinter : ASTVisitor
 	{
 		output.writeln("<xorExpression>");
 		output.writeln("<left>");
-		xorExpression.left.accept(this);
+		visit(xorExpression.left);
 		output.writeln("</left>");
 		if (xorExpression.right !is null)
 		{
 			output.writeln("<right>");
-			xorExpression.right.accept(this);
+			visit(xorExpression.right);
 			output.writeln("</right>");
 		}
 		output.writeln("</xorExpression>");