compilerplugins/clang/store/defaultparams.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 "plugin.hxx"
  14
  15 // Find places where we call a method with values == the values specified in the parameter defaults.
  16 // i.e. where the code might as well not specify anything.
  17
  18 namespace {
  19
  20 class DefaultParams:
  21     public loplugin::FilteringPlugin<DefaultParams>
  22 {
  23 public:
  24     explicit DefaultParams(InstantiationData const & data): FilteringPlugin(data) {}
  25
  26     virtual void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  27
  28     bool VisitCallExpr(CallExpr * callExpr);
  29 private:
  30     bool evaluate(const Expr* expr, APSInt& x);
  31 };
  32
  33 bool DefaultParams::VisitCallExpr(CallExpr * callExpr) {
  34     if (ignoreLocation(callExpr)) {
  35         return true;
  36     }
  37     if (callExpr->getDirectCallee() == nullptr) {
  38         return true;
  39     }
  40     const FunctionDecl* functionDecl = callExpr->getDirectCallee()->getCanonicalDecl();
  41     auto n = functionDecl->getNumParams();
  42     if (n == 0 || !functionDecl->getParamDecl(n - 1)->hasDefaultArg()) {
  43         return true;
  44     }
  45     assert(callExpr->getNumArgs() <= n); // can be < in template code
  46     for (unsigned i = callExpr->getNumArgs(); i != 0;) {
  47         --i;
  48         Expr* arg = callExpr->getArg(i);
  49         if (arg->isDefaultArgument()) {
  50             continue;
  51         }
  52         // ignore this, it seems to trigger an infinite recursion
  53         if (isa<UnaryExprOrTypeTraitExpr>(arg))
  54             break;
  55         const ParmVarDecl* parmVarDecl = functionDecl->getParamDecl(i);
  56         if (!parmVarDecl->hasDefaultArg()
  57             || parmVarDecl->hasUninstantiatedDefaultArg())
  58         {
  59             break;
  60         }
  61         const Expr* defaultArgExpr = parmVarDecl->getDefaultArg();
  62         if (!defaultArgExpr) {
  63             break;
  64         }
  65         bool found = false;
  66         if (defaultArgExpr->isNullPointerConstant(compiler.getASTContext(), Expr::NPC_NeverValueDependent)
  67             && arg->isNullPointerConstant(compiler.getASTContext(), Expr::NPC_NeverValueDependent))
  68         {
  69             found = true;
  70         }
  71         if (!found)
  72         {
  73             APSInt x1, x2;
  74             if (evaluate(defaultArgExpr, x1) && evaluate(arg, x2) && x1 == x2)
  75             {
  76                 found = true;
  77             }
  78         }
  79         // catch params with defaults like "= OUString()"
  80         if (!found
  81             && isa<MaterializeTemporaryExpr>(arg)
  82             && isa<MaterializeTemporaryExpr>(defaultArgExpr))
  83         {
  84             const CXXBindTemporaryExpr* strippedArg = dyn_cast_or_null<CXXBindTemporaryExpr>(arg->IgnoreParenCasts());
  85             if (strippedArg && isa<CXXTemporaryObjectExpr>(strippedArg->getSubExpr())
  86                 && dyn_cast<CXXTemporaryObjectExpr>(strippedArg->getSubExpr())->getNumArgs() == 0)
  87             {
  88                 found = true;
  89             }
  90         }
  91         if (!found)
  92             break;
  93         // Ignore CPPUNIT, it's macros contain some stuff that triggers us
  94         StringRef aFileName = compiler.getSourceManager().getFilename(compiler.getSourceManager().getSpellingLoc(parmVarDecl->getLocStart()));
  95         if (aFileName.find("include/cppunit") != std::string::npos)
  96             break;
  97         report(
  98             DiagnosticsEngine::Warning,
  99             "not necessary to pass this argument, it defaults to the same value",
 100             arg->getSourceRange().getBegin())
 101             << arg->getSourceRange();
 102         report(
 103             DiagnosticsEngine::Note,
 104             "default method parameter declaration here",
 105             parmVarDecl->getSourceRange().getBegin())
 106             << parmVarDecl->getSourceRange();
 107     }
 108     return true;
 109 }
 110
 111 bool DefaultParams::evaluate(const Expr* expr, APSInt& x)
 112 {
 113     if (isa<CXXNullPtrLiteralExpr>(expr)) {
 114         x = 0;
 115         return true;
 116     }
 117     if (expr->EvaluateAsInt(x, compiler.getASTContext()))
 118     {
 119         return true;
 120     }
 121     return false;
 122 }
 123
 124 loplugin::Plugin::Registration< DefaultParams > X("defaultparams");
 125
 126 }
 127
 128 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */