compilerplugins/clang/store/tutorial/tutorial2.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * Based on LLVM/Clang.
   6  *
   7  * This file is distributed under the University of Illinois Open Source
   8  * License. See LICENSE.TXT for details.
   9  *
  10  */
  11
  12 #include "tutorial2.hxx"
  13
  14 /*
  15 This is a compile check.
  16
  17 Warns about if statements with a comparison followed by literal return false:
  18 if( a == 1 )
  19     return false;
  20 */
  21
  22 namespace loplugin
  23 {
  24
  25 Tutorial2::Tutorial2( const InstantiationData& data )
  26     : FilteringPlugin( data )
  27     {
  28     }
  29
  30 void Tutorial2::run()
  31     {
  32     // The Clang AST helper class will call VisitIfStmt for every if statement.
  33     TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
  34     }
  35
  36 // This function is called for every if statement.
  37 bool Tutorial2::VisitIfStmt( const IfStmt* ifstmt )
  38     {
  39     if( ignoreLocation( ifstmt ))
  40         return true;
  41     // Check if the condition of the if statement is a binary operator.
  42     if( const BinaryOperator* oper = dyn_cast< BinaryOperator >( ifstmt->getCond()))
  43         {
  44         // And if it's operator==.
  45         if( oper->getOpcode() == BO_EQ )
  46             {
  47             // Now check if the sub-statement is 'return false'.
  48             const Stmt* warn = NULL; // The return statement (for the warning message).
  49             // Check if the sub-statement is directly 'return false;'.
  50             if( isReturnFalse( ifstmt->getThen()))
  51                 warn = ifstmt->getThen();
  52             // Check if the sub-statement is '{ return false; }'
  53             else if( const CompoundStmt* compound = dyn_cast< CompoundStmt >( ifstmt->getThen()))
  54                 {
  55                 if( compound->size() == 1 ) // one statement
  56                     if( isReturnFalse( *compound->body_begin())) // check the one sub-statement
  57                         warn = *compound->body_begin();
  58                 }
  59             if( warn != NULL ) // there is a return statement to warn about.
  60                 {
  61                 report( DiagnosticsEngine::Warning,
  62                     "returning false after if with equality comparison",
  63                     cast< ReturnStmt >( warn )->getRetValue()->getLocStart()) // the 'false' in the return
  64                     << warn->getSourceRange();
  65                 // Also add a note showing the if statement.
  66                 report( DiagnosticsEngine::Note,
  67                     "the if statement is here",
  68                     ifstmt->getLocStart());
  69                 }
  70             }
  71         }
  72     return true;
  73     }
  74
  75 bool Tutorial2::isReturnFalse( const Stmt* stmt )
  76     {
  77     // Is it return statement?
  78     if( const ReturnStmt* returnstmt = dyn_cast< ReturnStmt >( stmt ))
  79         {
  80         // dyn_cast_or_null<> can also be passed NULL, unlike dyn_cast<>
  81         if( const CXXBoolLiteralExpr* boolliteral = dyn_cast_or_null< CXXBoolLiteralExpr >( returnstmt->getRetValue()))
  82             {
  83             if( boolliteral->getValue() == false )
  84                 return true;
  85             }
  86         }
  87     return false;
  88     }
  89
  90 // Register the plugin action with the LO plugin handling.
  91 static Plugin::Registration< Tutorial2 > tutorial2( "tutorial2" );
  92
  93 } // namespace
  94
  95 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */