compilerplugins/clang/returnconstval.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  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9 #ifndef LO_CLANG_SHARED_PLUGINS
  10
  11 #include <string>
  12 #include <set>
  13
  14 #include "plugin.hxx"
  15
  16 /**
  17   Find code where we are return a const value type from a function.
  18   Which makes no sense.
  19   Either we should return by non-const value, or by const ref.
  20   e.g.
  21     struct S2 {
  22         OUString mv1;
  23         const OUString get13() { return mv1; }
  24     }
  25
  26   Specifically, this code pattern will prevent copy/move optimisations.
  27 */
  28
  29 namespace
  30 {
  31 class ReturnConstVal : public loplugin::FilteringPlugin<ReturnConstVal>
  32 {
  33 public:
  34     explicit ReturnConstVal(loplugin::InstantiationData const& data)
  35         : FilteringPlugin(data)
  36     {
  37     }
  38
  39     virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  40
  41     bool VisitFunctionDecl(const FunctionDecl* decl);
  42 };
  43
  44 bool ReturnConstVal::VisitFunctionDecl(const FunctionDecl* functionDecl)
  45 {
  46     if (ignoreLocation(functionDecl))
  47         return true;
  48     if (!functionDecl->hasBody())
  49         return true;
  50     // ignore stuff that forms part of the stable URE interface
  51     if (isInUnoIncludeFile(functionDecl))
  52         return true;
  53     QualType t1{ functionDecl->getReturnType() };
  54     if (!t1.isConstQualified())
  55         return true;
  56     if (t1->isReferenceType())
  57         return true;
  58     report(DiagnosticsEngine::Warning, "either return non-const, or by const ref",
  59            functionDecl->getSourceRange().getBegin())
  60         << functionDecl->getSourceRange();
  61
  62     // display the location of the class member declaration so I don't have to search for it by hand
  63     auto canonicalDecl = functionDecl->getCanonicalDecl();
  64     if (canonicalDecl != functionDecl)
  65     {
  66         report(DiagnosticsEngine::Note, "either return non-const, or by const ref",
  67                canonicalDecl->getSourceRange().getBegin())
  68             << canonicalDecl->getSourceRange();
  69     }
  70
  71     return true;
  72 }
  73
  74 loplugin::Plugin::Registration<ReturnConstVal> returnconstval("returnconstval");
  75 }
  76
  77 #endif // LO_CLANG_SHARED_PLUGINS
  78
  79 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */