compilerplugins/clang/rangedforcopy.cxx

   1
   2 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   3 /*
   4  * This file is part of the LibreOffice project.
   5  *
   6  * This Source Code Form is subject to the terms of the Mozilla Public
   7  * License, v. 2.0. If a copy of the MPL was not distributed with this
   8  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   9  */
  10 #ifndef LO_CLANG_SHARED_PLUGINS
  11
  12 #include <string>
  13 #include <iostream>
  14
  15 #include "check.hxx"
  16 #include "plugin.hxx"
  17 #include "clang/AST/CXXInheritance.h"
  18
  19 // Check that we're not unnecessarily copying variables in a range based for loop
  20 // e.g. "for (OUString a: aList)" results in a copy of each string being made,
  21 // whereas "for (const OUString& a: aList)" does not.
  22
  23 namespace
  24 {
  25
  26 class RangedForCopy:
  27     public loplugin::FilteringPlugin<RangedForCopy>
  28 {
  29 public:
  30     explicit RangedForCopy(loplugin::InstantiationData const & data):
  31         FilteringPlugin(data) {}
  32
  33     virtual void run() override {
  34         if (preRun())
  35             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
  36     }
  37
  38     bool VisitCXXForRangeStmt( const CXXForRangeStmt* stmt );
  39 };
  40
  41 bool RangedForCopy::VisitCXXForRangeStmt( const CXXForRangeStmt* stmt )
  42 {
  43     if (ignoreLocation( stmt ))
  44         return true;
  45
  46     const VarDecl* varDecl = stmt->getLoopVariable();
  47     if (!varDecl)
  48       return true;
  49     if (isa<DecompositionDecl>(varDecl))
  50     {
  51         // Assume that use of a non-reference structured binding is intentional:
  52         return true;
  53     }
  54
  55     const QualType type = varDecl->getType();
  56     if (type->isRecordType() && !type->isReferenceType() && !type->isPointerType())
  57     {
  58         if (loplugin::TypeCheck(type).Class("__bit_const_reference").StdNamespace())
  59         {
  60             // With libc++ without _LIBCPP_ABI_BITSET_VECTOR_BOOL_CONST_SUBSCRIPT_RETURN_BOOL,
  61             // iterating over a const std::vector<bool> non-compliantly uses a variable of some
  62             // internal __bit_const_reference class type, rather than of type bool (see
  63             // <https://reviews.llvm.org/D123851> "[libc++] Change
  64             // vector<bool>::const_iterator::reference to bool in ABIv2"):
  65             return true;
  66         }
  67         std::string name = type.getAsString();
  68         report(
  69                DiagnosticsEngine::Warning,
  70                "Loop variable passed by value, pass by reference instead, e.g. 'const %0&'",
  71                varDecl->getBeginLoc())
  72                << name << varDecl->getSourceRange();
  73     }
  74
  75     return true;
  76 }
  77
  78
  79 loplugin::Plugin::Registration< RangedForCopy > rangedforcopy("rangedforcopy");
  80
  81 } // namespace
  82
  83 #endif // LO_CLANG_SHARED_PLUGINS
  84
  85 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */