compilerplugins/clang/unusedindex.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
  11 #include <string>
  12 #include <iostream>
  13 #include <unordered_set>
  14
  15 #include "plugin.hxx"
  16 #include "check.hxx"
  17 #include "clang/AST/CXXInheritance.h"
  18 #include "clang/AST/StmtVisitor.h"
  19
  20 /*
  21  Mike Kaganski found a bug where the code was looping over a block and
  22  not using the index var, and the loop was unnecessary.
  23  So he wanted to have a look for other places like that.
  24 */
  25 namespace
  26 {
  27 class UnusedIndex : public RecursiveASTVisitor<UnusedIndex>, public loplugin::Plugin
  28 {
  29 public:
  30     explicit UnusedIndex(loplugin::InstantiationData const& data)
  31         : Plugin(data)
  32     {
  33     }
  34
  35     virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  36
  37     bool TraverseForStmt(ForStmt* stmt);
  38     bool VisitDeclRefExpr(DeclRefExpr const* stmt);
  39
  40 private:
  41     std::vector<VarDecl const*> mLoopVarDecls;
  42     std::unordered_set<VarDecl const*> mFoundSet;
  43 };
  44
  45 bool UnusedIndex::TraverseForStmt(ForStmt* stmt)
  46 {
  47     if (ignoreLocation(stmt))
  48         return true;
  49
  50     VarDecl const* loopVarDecl = nullptr;
  51     if (stmt->getInit())
  52     {
  53         auto declStmt = dyn_cast<DeclStmt>(stmt->getInit());
  54         if (declStmt && declStmt->isSingleDecl())
  55         {
  56             loopVarDecl = dyn_cast<VarDecl>(declStmt->getSingleDecl());
  57         }
  58     }
  59     if (loopVarDecl)
  60         mLoopVarDecls.push_back(loopVarDecl);
  61
  62     // deliberately ignore the other parts of the for stmt, except for the body
  63     auto ret = RecursiveASTVisitor::TraverseStmt(stmt->getBody());
  64
  65     if (loopVarDecl && mFoundSet.erase(loopVarDecl) == 0)
  66         report(DiagnosticsEngine::Warning, "loop variable not used", loopVarDecl->getLocStart())
  67             << loopVarDecl->getSourceRange();
  68
  69     if (loopVarDecl)
  70         mLoopVarDecls.pop_back();
  71     return ret;
  72 }
  73
  74 bool UnusedIndex::VisitDeclRefExpr(DeclRefExpr const* stmt)
  75 {
  76     auto varDecl = dyn_cast<VarDecl>(stmt->getDecl());
  77     if (!varDecl)
  78         return true;
  79     if (std::find(mLoopVarDecls.begin(), mLoopVarDecls.end(), varDecl) != mLoopVarDecls.end())
  80         mFoundSet.insert(varDecl);
  81     return true;
  82 }
  83
  84 loplugin::Plugin::Registration<UnusedIndex> X("unusedindex", false);
  85 }
  86
  87 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */