compilerplugins/clang/returnbyref.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
  10 #include <string>
  11 #include <set>
  12
  13 #include "compat.hxx"
  14 #include "plugin.hxx"
  15
  16 // Find places where we are returning a pointer to something, where we can be returning a reference.
  17 // e.g.
  18 //   class A {
  19 //     struct X x;
  20 //     public:
  21 //     X* getX() { return &x; }
  22 //   }
  23 // which can be:
  24 //     X& getX() { return x; }
  25
  26 namespace {
  27
  28 class ReturnByRef:
  29     public RecursiveASTVisitor<ReturnByRef>, public loplugin::Plugin
  30 {
  31 public:
  32     explicit ReturnByRef(InstantiationData const & data): Plugin(data) {}
  33
  34     virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  35
  36     bool VisitCXXMethodDecl(const CXXMethodDecl * decl);
  37 };
  38
  39 bool ReturnByRef::VisitCXXMethodDecl(const CXXMethodDecl * functionDecl) {
  40     if (ignoreLocation(functionDecl)) {
  41         return true;
  42     }
  43     if (functionDecl->isVirtual()) {
  44         return true;
  45     }
  46     if (!functionDecl->isInstance()) {
  47         return true;
  48     }
  49     if (!functionDecl->hasBody()) {
  50         return true;
  51     }
  52     // ignore stuff that forms part of the stable URE interface
  53     if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(
  54                               functionDecl->getCanonicalDecl()->getNameInfo().getLoc()))) {
  55         return true;
  56     }
  57     QualType t1 { compat::getReturnType(*functionDecl) };
  58     if (!t1->isPointerType()) {
  59         return true;
  60     }
  61     // Ignore stuff like:
  62     //   operator vcl::Window *(){ return &m_rWindow; }
  63     if (dyn_cast< CXXConversionDecl >( functionDecl ) != nullptr) {
  64         return true;
  65     }
  66
  67     /*
  68       The AST here looks like:
  69       -CompoundStmt
  70        `-ReturnStmt
  71           `-UnaryOperator
  72             `-MemberExpr
  73               `-CXXThisExpr
  74     */
  75
  76     const CompoundStmt* compoundStmt = dyn_cast< CompoundStmt >( functionDecl->getBody() );
  77     if (compoundStmt == nullptr || compoundStmt->body_begin() == compoundStmt->body_end()) {
  78         return true;
  79     }
  80     const ReturnStmt* returnStmt = dyn_cast<ReturnStmt>(*compoundStmt->child_begin());
  81     if (returnStmt == nullptr) {
  82         return true;
  83     }
  84
  85     const Stmt* nextStmt = dyn_cast<Expr>(*returnStmt->child_begin())->IgnoreParens();
  86     const UnaryOperator* unaryOperator = dyn_cast<UnaryOperator>(nextStmt);
  87     if (unaryOperator == nullptr || unaryOperator->getOpcode() != UO_AddrOf) {
  88         return true;
  89     }
  90
  91     nextStmt = dyn_cast<Expr>(*unaryOperator->child_begin())->IgnoreParens();
  92     const MemberExpr* memberExpr = dyn_cast<MemberExpr>(nextStmt);
  93     if (memberExpr == nullptr) {
  94         return true;
  95     }
  96
  97     nextStmt = dyn_cast<Expr>(*memberExpr->child_begin())->IgnoreParens();
  98     const CXXThisExpr* cXXThisExpr = dyn_cast<CXXThisExpr>(nextStmt);
  99     if (cXXThisExpr == nullptr) {
 100         return true;
 101     }
 102
 103     report(
 104         DiagnosticsEngine::Warning,
 105         "rather return by reference",
 106         functionDecl->getSourceRange().getBegin())
 107       << functionDecl->getSourceRange();
 108     // display the location of the class member declaration so I don't have to search for it by hand
 109     report(
 110         DiagnosticsEngine::Note,
 111         "rather return by reference",
 112         functionDecl->getCanonicalDecl()->getSourceRange().getBegin())
 113       << functionDecl->getCanonicalDecl()->getSourceRange();
 114
 115     return true;
 116 }
 117
 118 loplugin::Plugin::Registration< ReturnByRef > X("returnbyref");
 119
 120 }
 121
 122 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */