new loplugin intvsfloat

This was a good idea from mike kaganski as a consequence of
   https://gerrit.libreoffice.org/55359

Unfortunately, clang/llvm is not yet up to the job of doing floating
point evaluation, I get tons of crashes all over the evaluate
infrastruction inside clang, so this will need to wait until clang's
code matures.

So park it in store for now

Change-Id: I5ba4de8323e462b4fd4db301e4d116a81fd56ed3
Reviewed-on: https://gerrit.libreoffice.org/59254
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

compilerplugins/clang/store/intvsfloat.cxx

+/* -*- 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 "plugin.hxx"
+#include "check.hxx"
+#include "compat.hxx"
+#include <iostream>
+
+/**
+
+TODO multiplying/otherop on a combination of a float and int, and then truncating to int. like this:
+    float getRotation() {}
+    int moRotation;
+    moRotation = -F_PI180 * 90 * getRotation();
+
+*/
+namespace
+{
+class IntVsFloat : public loplugin::FilteringPlugin<IntVsFloat>
+{
+public:
+    explicit IntVsFloat(loplugin::InstantiationData const& data)
+        : loplugin::FilteringPlugin<IntVsFloat>(data)
+    {
+    }
+
+    void run() override { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }
+
+    bool VisitVarDecl(VarDecl const*);
+    bool VisitBinEQ(BinaryOperator const*);
+
+private:
+    llvm::Optional<double> getExprValue(Expr const* expr);
+};
+
+bool IntVsFloat::VisitVarDecl(VarDecl const* varDecl)
+{
+    if (ignoreLocation(varDecl->getLocation()))
+        return true;
+    auto init = varDecl->getInit();
+    if (!init)
+        return true;
+    init = init->IgnoreImpCasts();
+    if (varDecl->getType()->isFloatingType())
+        return true;
+    //    init->dump();
+    llvm::Optional<double> d = getExprValue(init);
+    if (!d)
+        return true;
+    if (static_cast<long>(*d) == *d)
+        return true;
+    report(DiagnosticsEngine::Warning, "assigning constant float value to int truncates data",
+           compat::getBeginLoc(init))
+        << init->getSourceRange();
+
+    return true;
+}
+
+bool IntVsFloat::VisitBinEQ(BinaryOperator const* op)
+{
+    if (ignoreLocation(compat::getBeginLoc(op)))
+        return true;
+    auto lhs = op->getLHS()->IgnoreImpCasts();
+    auto rhs = op->getRHS()->IgnoreImpCasts();
+    if (!lhs->getType()->isFloatingType())
+        std::swap(lhs, rhs);
+    if (!lhs->getType()->isFloatingType())
+        return true;
+    if (rhs->getType()->isFloatingType())
+        return true;
+    llvm::Optional<double> d = getExprValue(lhs);
+    if (!d)
+        return true;
+    if (static_cast<long>(*d) == *d)
+        return true;
+    report(DiagnosticsEngine::Warning, "comparing integer to float constant, can never be true",
+           compat::getBeginLoc(op))
+        << op->getSourceRange();
+    return true;
+}
+
+llvm::Optional<double> IntVsFloat::getExprValue(Expr const* expr)
+{
+    // Of the available clang Evaluate* APIs, this is the __only__ one that produces useful output
+    // (as of 17 Aug 2018 checkout of clang, ie. towards clang 7)
+
+    Expr::EvalResult evalResult;
+    if (!expr->EvaluateAsRValue(evalResult, compiler.getASTContext()))
+        return llvm::Optional<double>();
+    if (!evalResult.Val.isFloat())
+        return llvm::Optional<double>();
+    llvm::APFloat floatResult = evalResult.Val.getFloat();
+    bool losesInfo;
+    floatResult.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven, &losesInfo);
+
+    double d = floatResult.convertToDouble();
+    return d;
+}
+
+loplugin::Plugin::Registration<IntVsFloat> X("intvsfloat");
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */

compilerplugins/clang/test/intvsfloat.cxx

+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * 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/.
+ */
+
+static const float PI = 3.4;
+struct Class1
+{
+    float getFloat() const { return 1.5; }
+    int getInt() const { return 1; }
+    static constexpr float PI = 3.4;
+    static constexpr float E() { return 3.4; }
+};
+
+void func1(Class1 const& class1)
+{
+    if (1
+        == PI) // expected-error {{comparing integer to float constant, can never be true [loplugin:intvsfloat]}}
+        return;
+    if (1
+        == class1
+               .PI) // expected-error {{comparing integer to float constant, can never be true [loplugin:intvsfloat]}}
+        return;
+    if (true
+        == class1
+               .PI) // expected-error {{comparing integer to float constant, can never be true [loplugin:intvsfloat]}}
+        return;
+    if (1 == class1.getInt()) // no warning expected
+        return;
+    if (1
+        == class1
+               .E()) // expected-error {{comparing integer to float constant, can never be true [loplugin:intvsfloat]}}
+        return;
+    if (true
+        == class1
+               .E()) // expected-error {{comparing integer to float constant, can never be true [loplugin:intvsfloat]}}
+        return;
+    if (1 == class1.getFloat()) // no warning expected
+        return;
+}
+
+void func2(Class1 const& class1)
+{
+    int i0
+        = PI; // expected-error {{assigning constant float value to int truncates data [loplugin:intvsfloat]}}
+    (void)i0;
+    int i1
+        = class1
+              .PI; // expected-error {{assigning constant float value to int truncates data [loplugin:intvsfloat]}}
+    (void)i1;
+    int i2
+        = class1
+              .E(); // expected-error {{assigning constant float value to int truncates data [loplugin:intvsfloat]}}
+    (void)i2;
+    int i3 = class1.getFloat(); // no warning expected
+    (void)i3;
+    int i4 = class1.getInt(); // no warning expected
+    (void)i4;
+    bool b1
+        = class1
+              .E(); // expected-error {{assigning constant float value to int truncates data [loplugin:intvsfloat]}}
+    (void)b1;
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */