tutorial examples for writing new Clang plugin actions

http://wiki.documentfoundation.org/Clang_plugins

Change-Id: Ieb4fc186490e81ab961c094ca0a7fcdabc0f348f

compilerplugins/clang/store/tutorial/tutorial3.cxx

@@ -0,0 +1,74 @@
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * Based on LLVM/Clang.
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ *
+ */
+
+#include "tutorial3.hxx"
+
+/*
+This is a rewriter.
+
+It looks for if statements with a comparison followed by literal return false
+and modifies the return statements to 'return maybereturntrue;'
+*/
+
+namespace loplugin
+{
+
+// Ctor, pass arguments.
+Tutorial3::Tutorial3( ASTContext& context, Rewriter& rewriter )
+    : RewritePlugin( context, rewriter )
+    {
+    }
+
+void Tutorial3::run()
+    {
+    TraverseDecl( context.getTranslationUnitDecl());
+    }
+
+bool Tutorial3::VisitIfStmt( IfStmt* ifstmt )
+    {
+    if( ignoreLocation( ifstmt ))
+        return true;
+    if( const BinaryOperator* oper = dyn_cast< BinaryOperator >( ifstmt->getCond()))
+        {
+        if( oper->getOpcode() == BO_EQ )
+            {
+            // Modify the sub-statement if it is 'return false'.
+            modifyReturnFalse( ifstmt->getThen());
+            // Modify the sub-statement if it is '{ return false; }'.
+            if( CompoundStmt* compound = dyn_cast< CompoundStmt >( ifstmt->getThen()))
+                {
+                if( compound->size() == 1 ) // one statement
+                    modifyReturnFalse( *compound->body_begin());
+                }
+            }
+        }
+    return true;
+    }
+
+void Tutorial3::modifyReturnFalse( const Stmt* stmt )
+    {
+    // Is it return statement?
+    if( const ReturnStmt* returnstmt = dyn_cast< ReturnStmt >( stmt ))
+        {
+        // dyn_cast_or_null<> can also be passed NULL, unlike dyn_cast<>
+        if( const CXXBoolLiteralExpr* boolliteral = dyn_cast_or_null< CXXBoolLiteralExpr >( returnstmt->getRetValue()))
+            {
+            if( boolliteral->getValue() == false )
+                { // It is, modify the false to true using LO plugin helper function.
+                replaceText( boolliteral->getSourceRange(), "maybereturntrue" );
+                }
+            }
+        }
+    }
+
+// Register the plugin action with the LO plugin handling.
+static Plugin::Registration< Tutorial3 > X( "tutorial3" );
+
+} // namespace