compilerplugins/clang/cow_wrapper.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 #ifndef LO_CLANG_SHARED_PLUGINS
  12
  13 #include <cassert>
  14 #include <string>
  15 #include <iostream>
  16 #include <fstream>
  17 #include <set>
  18 #include <unordered_set>
  19 #include "plugin.hxx"
  20 #include "check.hxx"
  21
  22 /*
  23 Look for places where we are using cow_wrapper, but we are calling a const method on the impl object
  24 with a non-const pointer, which means we will unnecessarily trigger a copy.
  25 */
  26
  27 namespace
  28 {
  29 class Cow_Wrapper : public loplugin::FilteringPlugin<Cow_Wrapper>
  30 {
  31 public:
  32     explicit Cow_Wrapper(loplugin::InstantiationData const& data)
  33         : FilteringPlugin(data)
  34     {
  35     }
  36
  37     bool shouldVisitTemplateInstantiations() const { return true; }
  38
  39     virtual bool preRun() override { return true; }
  40
  41     virtual void run() override
  42     {
  43         if (preRun())
  44             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
  45     }
  46
  47     bool VisitCXXMemberCallExpr(const CXXMemberCallExpr*);
  48 };
  49
  50 bool Cow_Wrapper::VisitCXXMemberCallExpr(const CXXMemberCallExpr* memberCallExpr)
  51 {
  52     if (ignoreLocation(memberCallExpr))
  53         return true;
  54     auto methodDecl = memberCallExpr->getMethodDecl();
  55     if (!methodDecl || !methodDecl->isConst())
  56         return true;
  57
  58     auto expr = memberCallExpr->getImplicitObjectArgument()->IgnoreImplicit()->IgnoreParens();
  59     auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(expr);
  60
  61     if (operatorCallExpr && operatorCallExpr->getOperator() == OO_Arrow)
  62     {
  63         auto arrowMethodDecl = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
  64         if (!arrowMethodDecl)
  65             return true;
  66         if (arrowMethodDecl->isConst())
  67             return true;
  68         auto dc = loplugin::DeclCheck(arrowMethodDecl->getParent())
  69                       .Class("cow_wrapper")
  70                       .Namespace("o3tl")
  71                       .GlobalNamespace();
  72         if (!dc)
  73             return true;
  74     }
  75     else if (operatorCallExpr)
  76     {
  77         auto methodDecl2 = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
  78         if (!methodDecl2)
  79             return true;
  80         auto dc = loplugin::DeclCheck(methodDecl2->getParent())
  81                       .Class("cow_wrapper")
  82                       .Namespace("o3tl")
  83                       .GlobalNamespace();
  84         if (!dc)
  85             return true;
  86     }
  87     else if (auto callExpr = dyn_cast<CallExpr>(expr))
  88     {
  89         if (!isa<ImplicitCastExpr>(callExpr->getCallee())) // std::as_const shows up as this
  90             return true;
  91         if (callExpr->getNumArgs() < 1)
  92             return true;
  93         auto arg0 = dyn_cast<CXXOperatorCallExpr>(callExpr->getArg(0));
  94         if (!arg0)
  95             return true;
  96         auto starMethodDecl = dyn_cast_or_null<CXXMethodDecl>(arg0->getDirectCallee());
  97         if (!starMethodDecl)
  98             return true;
  99         auto dc = loplugin::DeclCheck(starMethodDecl->getParent())
 100                       .Class("cow_wrapper")
 101                       .Namespace("o3tl")
 102                       .GlobalNamespace();
 103         if (!dc)
 104             return true;
 105     }
 106     else
 107         return true;
 108
 109     report(DiagnosticsEngine::Warning,
 110            "calling const method on o3tl::cow_wrapper impl class via non-const pointer, rather use "
 111            "std::as_const to prevent triggering an unnecessary copy",
 112            memberCallExpr->getBeginLoc())
 113         << memberCallExpr->getSourceRange();
 114     return true;
 115 }
 116
 117 loplugin::Plugin::Registration<Cow_Wrapper> cow_wrapper("cow_wrapper", true);
 118
 119 } // namespace
 120
 121 #endif // LO_CLANG_SHARED_PLUGINS
 122
 123 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */