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 #include <config_global.h>
  13
  14 // If there is support for warn_unused attribute even in STL classes, then there's
  15 // no point in having this check enabled, otherwise keep it at least for STL
  16 // (LO classes won't get duplicated warnings, as the attribute is different).
  17 #if !HAVE_GCC_ATTRIBUTE_WARN_UNUSED_STL
  18
  19 #include "unusedvariablecheck.hxx"
  20
  21 #include <clang/AST/Attr.h>
  22
  23 namespace loplugin
  24 {
  25
  26 /*
  27 This is a compile check.
  28
  29 Check for unused classes where the compiler cannot decide (e.g. because of
  30 non-trivial or extern ctors) if a variable is unused if only its ctor/dtor
  31 are called and nothing else. For example std::vector is a class where
  32 the ctor may call further functions, but an unused std::string variable
  33 does nothing. On the other hand, std::lock_guard instances are used
  34 for their dtors and so are not unused even if not otherwise accessed.
  35
  36 Classes which are safe to be warned about need to be marked using
  37 SAL_WARN_UNUSED (see e.g. OUString). For external classes such as std::vector
  38 that cannot be edited there is a manual list below.
  39 */
  40
  41 UnusedVariableCheck::UnusedVariableCheck( const InstantiationData& data )
  42     : Plugin( data )
  43     {
  44     }
  45
  46 void UnusedVariableCheck::run()
  47     {
  48     TraverseDecl( compiler.getASTContext().getTranslationUnitDecl());
  49     }
  50
  51 bool BaseCheckNotDialogSubclass(const CXXRecordDecl *BaseDefinition, void *) {
  52     if (BaseDefinition && BaseDefinition->getQualifiedNameAsString().compare("Dialog") == 0) {
  53         return false;
  54     }
  55     return true;
  56 }
  57
  58 bool isDerivedFromDialog(const CXXRecordDecl *decl) {
  59     if (!decl)
  60         return false;
  61     if (decl->getQualifiedNameAsString() == "Dialog")
  62         return true;
  63     if (!decl->hasDefinition()) {
  64         return false;
  65     }
  66     if (// not sure what hasAnyDependentBases() does,
  67         // but it avoids classes we don't want, e.g. WeakAggComponentImplHelper1
  68         !decl->hasAnyDependentBases() &&
  69         !decl->forallBases(BaseCheckNotDialogSubclass, nullptr, true)) {
  70         return true;
  71     }
  72     return false;
  73 }
  74
  75 bool UnusedVariableCheck::VisitVarDecl( const VarDecl* var )
  76     {
  77     if( ignoreLocation( var ))
  78         return true;
  79     if( var->isReferenced() || var->isUsed())
  80         return true;
  81     if( var->isDefinedOutsideFunctionOrMethod())
  82         return true;
  83     if( CXXRecordDecl* type = var->getType()->getAsCXXRecordDecl())
  84         {
  85         bool warn_unused = false;
  86         if( type->hasAttrs())
  87             {
  88             // Clang currently has no support for custom attributes, but
  89             // the annotate attribute comes close, so check for __attribute__((annotate("lo_warn_unused")))
  90             for( specific_attr_iterator<AnnotateAttr> i = type->specific_attr_begin<AnnotateAttr>(),
  91                     e = type->specific_attr_end<AnnotateAttr>();
  92                  i != e;
  93                  ++i )
  94                 {
  95                 if( (*i)->getAnnotation() == "lo_warn_unused" )
  96                     {
  97                     warn_unused = true;
  98                     break;
  99                     }
 100                 }
 101             }
 102         if( !warn_unused )
 103             {
 104             string n = type->getQualifiedNameAsString();
 105             // Check some common non-LO types.
 106             if( n == "std::string" || n == "std::basic_string"
 107                 || n == "std::list" || n == "std::__debug::list"
 108                 || n == "std::vector" || n == "std::__debug::vector" )
 109                 warn_unused = true;
 110             // check if this field is derived from Dialog
 111             if (!warn_unused && isDerivedFromDialog(type))
 112                   warn_unused = true;
 113             }
 114         if( warn_unused )
 115             {
 116             if( const ParmVarDecl* param = dyn_cast< ParmVarDecl >( var ))
 117                 {
 118                 if( !param->getDeclName())
 119                     return true; // unnamed parameter -> unused
 120                 // If this declaration does not have a body, then the parameter is indeed not used,
 121                 // so ignore.
 122                 if( const FunctionDecl* func = dyn_cast_or_null< FunctionDecl >( param->getParentFunctionOrMethod()))
 123                     if( !func->doesThisDeclarationHaveABody())
 124                         return true;
 125                 report( DiagnosticsEngine::Warning, "unused parameter %0",
 126                     var->getLocation()) << var->getDeclName();
 127                 }
 128             else
 129                 report( DiagnosticsEngine::Warning, "unused variable %0",
 130                     var->getLocation()) << var->getDeclName();
 131             }
 132         }
 133     return true;
 134     }
 135
 136 static Plugin::Registration< UnusedVariableCheck > X( "unusedvariablecheck" );
 137
 138 } // namespace
 139
 140 #endif
 141
 142 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */