new loplugin fpcomparison

Find code that compares floating point values with == or !=
It should rather use rtl::math::approxEqual

Change-Id: I9026e08823340fa1d6a042c430515344c93215bd
Reviewed-on: https://gerrit.libreoffice.org/21997
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>

1 files changed, 146 insertions, 0 deletions

diff --git a/compilerplugins/clang/fpcomparison.cxx b/compilerplugins/clang/fpcomparison.cxx
new file mode 100644
index 000000000000..b374da7a5da7
--- /dev/null
+++ b/compilerplugins/clang/fpcomparison.cxx
@@ -0,0 +1,146 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <cassert>
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <set>
+#include "plugin.hxx"
+#include "compat.hxx"
+
+/**
+comparing floating point numbers using == or != is a bad idea.
+*/
+
+namespace {
+
+class FpComparison:
+    public RecursiveASTVisitor<FpComparison>, public loplugin::Plugin
+{
+public:
+    explicit FpComparison(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override
+    {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitBinaryOperator(const BinaryOperator* );
+    bool TraverseFunctionDecl(FunctionDecl* );
+private:
+    bool ignore(FunctionDecl* );
+    enum class EState { None, TraverseProcess, TraverseIgnore };
+    EState meState = EState::None;
+};
+
+static const std::set<std::string> whitelist {
+    "rtl::math::approxEqual",
+    "(anonymous namespace)::doubleToString",
+    "(anonymous namespace)::stringToDouble",
+    "rtl_math_round",
+    "rtl_math_approxValue",
+    "rtl_math_asinh",
+    "rtl_math_acosh",
+    "cppu::_equalSequence", // cppu/source/uno/eq.hxx
+    "cppu::_equalData", // cppu/source/uno/eq.hxx
+    "xmlscript::equalFont", // xmlscript/source/xmldlg_imexp/xmldlg_export.cxx
+
+    // these might need fixing
+    "basegfx::tools::getSmallestDistancePointToPolygon", // basegfx/source/polygon/b2dpolygontools.cxx
+    "basegfx::tools::getSmallestDistancePointToPolyPolygon", // basegfx/source/polygon/b2dpolypolygontools.cxx
+    "bridge_test::performTest", // testtools/source/bridgetest/bridgetest.cxx
+    "bridge_test::equals",
+    "(anonymous namespace)::lcl_getNANInsteadDBL_MIN", // chart2/source/controller/chartapiwrapper/ChartDataWrapper.cxx
+};
+bool FpComparison::TraverseFunctionDecl(FunctionDecl* function)
+{
+    bool bIgnore = ignore(function);
+    meState = bIgnore ? EState::TraverseIgnore : EState::TraverseProcess;
+    bool bRet = RecursiveASTVisitor::TraverseFunctionDecl(function);
+    meState = EState::None;
+    return bRet;
+}
+
+bool FpComparison::ignore(FunctionDecl* function)
+{
+    if (ignoreLocation(function)) {
+        return true;
+    }
+    // we assume that these modules know what they are doing with FP stuff
+    StringRef aFileName = compiler.getSourceManager().getFilename(compiler.getSourceManager().getSpellingLoc(function->getLocStart()));
+    if (aFileName.startswith(SRCDIR "/sc/")) {
+        return true;
+    }
+    if (!function->doesThisDeclarationHaveABody()) {
+        return true;
+    }
+     // Ignore operator== and operator!=
+    if (function->getOverloadedOperator() == OO_EqualEqual
+        || function->getOverloadedOperator() == OO_ExclaimEqual) {
+        return true;
+    }
+    // ignore known good functions
+    std::string s = function->getQualifiedNameAsString();
+    if (whitelist.find(s) != whitelist.end()) {
+        return true;
+    }
+//    cout << "xxx " + function->getQualifiedNameAsString() << endl;
+    return false;
+}
+
+static bool isZeroConstant(ASTContext& context, const Expr* expr)
+{
+    // calling isCXX11ConstantExpr with non-arithmetic types sometimes results in a crash
+    if (!expr->getType()->isArithmeticType()) {
+        return false;
+    }
+    // prevent clang crash
+    if (!context.getLangOpts().CPlusPlus) {
+        return false;
+    }
+    APValue result;
+    if (expr->isCXX11ConstantExpr(context, &result)
+        && result.isFloat() && result.getFloat().isZero())
+    {
+        return true;
+    }
+    return false;
+}
+bool FpComparison::VisitBinaryOperator(const BinaryOperator* binaryOp)
+{
+    if (meState != EState::TraverseProcess || ignoreLocation(binaryOp)) {
+        return true;
+    }
+    if (binaryOp->getOpcode() != BO_EQ && binaryOp->getOpcode() != BO_NE) {
+        return true;
+    }
+    // comparison with zero is valid
+    if (isZeroConstant(compiler.getASTContext(), binaryOp->getLHS())
+        || isZeroConstant(compiler.getASTContext(), binaryOp->getRHS()))
+    {
+        return true;
+    }
+    QualType LHSStrippedType = binaryOp->getLHS()->IgnoreParenImpCasts()->getType();
+    QualType RHSStrippedType = binaryOp->getRHS()->IgnoreParenImpCasts()->getType();
+    if (LHSStrippedType->isFloatingType() && RHSStrippedType->isFloatingType()) {
+        report(
+            DiagnosticsEngine::Warning, "floating-point comparison",
+            binaryOp->getSourceRange().getBegin())
+          << binaryOp->getSourceRange();
+    }
+    return true;
+}
+
+
+loplugin::Plugin::Registration< FpComparison > X("fpcomparison", true);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */