compilerplugins/clang/intvsfloat.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 #ifndef LO_CLANG_SHARED_PLUGINS
  10
  11 #include "plugin.hxx"
  12 #include "check.hxx"
  13 #include "compat.hxx"
  14 #include <iostream>
  15
  16 /**
  17
  18 TODO multiplying/otherop on a combination of a float and int, and then truncating to int. like this:
  19     float getRotation() {}
  20     int moRotation = -F_PI180 * 90 * getRotation();
  21 */
  22 namespace
  23 {
  24 class IntVsFloat : public loplugin::FilteringPlugin<IntVsFloat>
  25 {
  26 public:
  27     explicit IntVsFloat(loplugin::InstantiationData const& data)
  28         : loplugin::FilteringPlugin<IntVsFloat>(data)
  29     {
  30     }
  31
  32     void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
  33
  34     bool VisitVarDecl(VarDecl const*);
  35     bool VisitBinaryOperator(BinaryOperator const*);
  36
  37 private:
  38     compat::optional<double> getExprValue(Expr const* expr);
  39 };
  40
  41 bool IntVsFloat::VisitVarDecl(VarDecl const* varDecl)
  42 {
  43     if (ignoreLocation(varDecl->getLocation()))
  44         return true;
  45     auto init = varDecl->getInit();
  46     if (!init)
  47         return true;
  48     init = init->IgnoreImpCasts();
  49     if (varDecl->getType()->isFloatingType())
  50         return true;
  51     //    init->dump();
  52     compat::optional<double> d = getExprValue(init);
  53     if (!d)
  54         return true;
  55     if (static_cast<long>(*d) == *d)
  56         return true;
  57     report(DiagnosticsEngine::Warning, "assigning constant float value to int truncates data",
  58            init->getBeginLoc())
  59         << init->getSourceRange();
  60
  61     return true;
  62 }
  63
  64 bool IntVsFloat::VisitBinaryOperator(BinaryOperator const* op)
  65 {
  66     if (op->getOpcode() != BO_EQ)
  67     {
  68         return true;
  69     }
  70     if (ignoreLocation(op->getBeginLoc()))
  71         return true;
  72     auto lhs = op->getLHS()->IgnoreImpCasts();
  73     auto rhs = op->getRHS()->IgnoreImpCasts();
  74     if (!lhs->getType()->isFloatingType())
  75         std::swap(lhs, rhs);
  76     if (!lhs->getType()->isFloatingType())
  77         return true;
  78     if (rhs->getType()->isFloatingType())
  79         return true;
  80     compat::optional<double> d = getExprValue(lhs);
  81     if (!d)
  82         return true;
  83     if (static_cast<long>(*d) == *d)
  84         return true;
  85     report(DiagnosticsEngine::Warning, "comparing integer to float constant, can never be true",
  86            op->getBeginLoc())
  87         << op->getSourceRange();
  88     return true;
  89 }
  90
  91 compat::optional<double> IntVsFloat::getExprValue(Expr const* expr)
  92 {
  93     // Of the available clang Evaluate* APIs, this is the __only__ one that produces useful output
  94     // (as of 17 Aug 2018 checkout of clang, ie. towards clang 7)
  95
  96     if (expr->isValueDependent())
  97         return compat::optional<double>();
  98     Expr::EvalResult evalResult;
  99     if (!expr->EvaluateAsRValue(evalResult, compiler.getASTContext()))
 100         return compat::optional<double>();
 101     if (!evalResult.Val.isFloat())
 102         return compat::optional<double>();
 103     llvm::APFloat floatResult = evalResult.Val.getFloat();
 104     bool losesInfo;
 105     floatResult.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven, &losesInfo);
 106
 107     double d = floatResult.convertToDouble();
 108     return d;
 109 }
 110
 111 loplugin::Plugin::Registration<IntVsFloat> intvsfloat("intvsfloat");
 112
 113 } // namespace
 114
 115 #endif // LO_CLANG_SHARED_PLUGINS
 116
 117 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */