compilerplugins/clang/unusedvariablecheck.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 #ifndef LO_CLANG_SHARED_PLUGINS
  13
  14 #include <config_global.h>
  15
  16 #include "compat.hxx"
  17 #include "check.hxx"
  18 #include "unusedvariablecheck.hxx"
  19
  20 namespace loplugin
  21 {
  22
  23 /*
  24 This is a compile check.
  25
  26 Check for unused classes where the compiler cannot decide (e.g. because of
  27 non-trivial or extern ctors) if a variable is unused if only its ctor/dtor
  28 are called and nothing else. For example std::vector is a class where
  29 the ctor may call further functions, but an unused std::string variable
  30 does nothing. On the other hand, std::lock_guard instances are used
  31 for their dtors and so are not unused even if not otherwise accessed.
  32
  33 Classes which are safe to be warned about need to be marked using
  34 SAL_WARN_UNUSED (see e.g. OUString). For external classes such as std::vector
  35 that cannot be edited there is a manual list below.
  36 */
  37
  38 UnusedVariableCheck::UnusedVariableCheck( const InstantiationData& data )
  39     : FilteringPlugin( data )
  40     {
  41     }
  42
  43 void UnusedVariableCheck::run()
  44     {
  45     TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
  46     }
  47
  48 bool UnusedVariableCheck::VisitVarDecl( const VarDecl* var )
  49     {
  50     if( ignoreLocation( var ))
  51         return true;
  52     if( var->isReferenced() || var->isUsed())
  53         return true;
  54     if( var->isDefinedOutsideFunctionOrMethod())
  55         return true;
  56
  57     auto type = var->getType();
  58     bool check = loplugin::isExtraWarnUnusedType(type);
  59
  60     // this chunk of logic generates false+, which is why we don't leave it on
  61 /*
  62     if (!check && type->isRecordType())
  63     {
  64         auto recordDecl
  65             = dyn_cast_or_null<CXXRecordDecl>(type->getAs<RecordType>()->getDecl());
  66         if (recordDecl && recordDecl->hasDefinition() && recordDecl->hasTrivialDestructor())
  67             check = true;
  68     }
  69 */
  70     if(check)
  71         {
  72             if( const ParmVarDecl* param = dyn_cast< ParmVarDecl >( var ))
  73                 {
  74                 if( !param->getDeclName())
  75                     return true; // unnamed parameter -> unused
  76                 // If this declaration does not have a body, then the parameter is indeed not used,
  77                 // so ignore.
  78                 if( const FunctionDecl* func = dyn_cast_or_null< FunctionDecl >( param->getParentFunctionOrMethod()))
  79                     if( !func->doesThisDeclarationHaveABody())
  80                         return true;
  81                 report( DiagnosticsEngine::Warning, "unused parameter %0",
  82                     var->getLocation()) << var->getDeclName();
  83                 }
  84             else
  85                 report( DiagnosticsEngine::Warning, "unused variable %0",
  86                     var->getLocation()) << var->getDeclName();
  87         }
  88     return true;
  89     }
  90
  91 static Plugin::Registration< UnusedVariableCheck > unusedvariablecheck( "unusedvariablecheck" );
  92
  93 } // namespace
  94
  95 #endif // LO_CLANG_SHARED_PLUGINS
  96
  97 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */