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     virtual bool preRun() override { return true; }
  38
  39     virtual void run() override
  40     {
  41         if (preRun())
  42             TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
  43     }
  44
  45     bool VisitCXXMemberCallExpr(const CXXMemberCallExpr*);
  46 };
  47
  48 bool Cow_Wrapper::VisitCXXMemberCallExpr(const CXXMemberCallExpr* memberCallExpr)
  49 {
  50     if (ignoreLocation(memberCallExpr))
  51         return true;
  52     auto methodDecl = memberCallExpr->getMethodDecl();
  53     if (!methodDecl || !methodDecl->isConst())
  54         return true;
  55
  56     auto expr = memberCallExpr->getImplicitObjectArgument()->IgnoreImplicit()->IgnoreParens();
  57     auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(expr);
  58
  59     if (operatorCallExpr && operatorCallExpr->getOperator() == OO_Arrow)
  60     {
  61         auto arrowMethodDecl = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
  62         if (!arrowMethodDecl)
  63             return true;
  64         if (arrowMethodDecl->isConst())
  65             return true;
  66         auto dc = loplugin::DeclCheck(arrowMethodDecl->getParent())
  67                       .Class("cow_wrapper")
  68                       .Namespace("o3tl")
  69                       .GlobalNamespace();
  70         if (!dc)
  71             return true;
  72     }
  73     else if (operatorCallExpr)
  74     {
  75         auto methodDecl2 = dyn_cast_or_null<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
  76         if (!methodDecl2)
  77             return true;
  78         auto dc = loplugin::DeclCheck(methodDecl2->getParent())
  79                       .Class("cow_wrapper")
  80                       .Namespace("o3tl")
  81                       .GlobalNamespace();
  82         if (!dc)
  83             return true;
  84     }
  85     else if (auto callExpr = dyn_cast<CallExpr>(expr))
  86     {
  87         if (!isa<ImplicitCastExpr>(callExpr->getCallee())) // std::as_const shows up as this
  88             return true;
  89         if (callExpr->getNumArgs() < 1)
  90             return true;
  91         auto arg0 = dyn_cast<CXXOperatorCallExpr>(callExpr->getArg(0));
  92         if (!arg0)
  93             return true;
  94         auto starMethodDecl = dyn_cast_or_null<CXXMethodDecl>(arg0->getDirectCallee());
  95         if (!starMethodDecl)
  96             return true;
  97         auto dc = loplugin::DeclCheck(starMethodDecl->getParent())
  98                       .Class("cow_wrapper")
  99                       .Namespace("o3tl")
 100                       .GlobalNamespace();
 101         if (!dc)
 102             return true;
 103     }
 104     else
 105         return true;
 106
 107     report(DiagnosticsEngine::Warning,
 108            "calling const method on o3tl::cow_wrapper impl class via non-const pointer, rather use "
 109            "std::as_const to prevent triggering an unnecessary copy",
 110            memberCallExpr->getBeginLoc())
 111         << memberCallExpr->getSourceRange();
 112     return true;
 113 }
 114
 115 loplugin::Plugin::Registration<Cow_Wrapper> cow_wrapper("cow_wrapper", true);
 116
 117 } // namespace
 118
 119 #endif // LO_CLANG_SHARED_PLUGINS
 120
 121 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */