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-rw-r--r--compilerplugins/clang/expressionalwayszero.cxx151
1 files changed, 151 insertions, 0 deletions
diff --git a/compilerplugins/clang/expressionalwayszero.cxx b/compilerplugins/clang/expressionalwayszero.cxx
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+++ b/compilerplugins/clang/expressionalwayszero.cxx
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+/* -*- 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 <string>
+#include <set>
+#include <iostream>
+#include <fstream>
+
+#include "plugin.hxx"
+#include "compat.hxx"
+#include "check.hxx"
+
+/**
+ Look for & and operator& expressions where the result is always zero.
+ Generally a mistake when people meant to use | or operator|
+*/
+
+namespace
+{
+class ExpressionAlwaysZero : public loplugin::FilteringPlugin<ExpressionAlwaysZero>
+{
+public:
+ explicit ExpressionAlwaysZero(loplugin::InstantiationData const& data)
+ : FilteringPlugin(data)
+ {
+ }
+
+ virtual void run() override
+ {
+ // don't use getMainFileID, it may return "<stdin>"
+ std::string fn(handler.getMainFileName());
+
+ loplugin::normalizeDotDotInFilePath(fn);
+ // encoding of constant value for binary file format
+ if (loplugin::hasPathnamePrefix(fn, SRCDIR "/package/source/zipapi/ZipFile.cxx"))
+ return;
+ // some auto-generated static data
+ if (loplugin::hasPathnamePrefix(fn, SRCDIR "/sal/textenc/tables.cxx"))
+ return;
+ // nested conditional defines that are not worth cleaning up
+ if (loplugin::hasPathnamePrefix(fn, SRCDIR "/opencl/source/openclwrapper.cxx"))
+ return;
+ // some kind of matrix calculation, the compiler will optimise it out anyway
+ if (loplugin::hasPathnamePrefix(fn, SRCDIR "/vcl/source/gdi/bitmap4.cxx"))
+ return;
+ // code follows a pattern
+ if (loplugin::hasPathnamePrefix(fn, SRCDIR "/svx/source/svdraw/svdhdl.cxx"))
+ return;
+ // looks like some kind of TODO marker
+ if (loplugin::hasPathnamePrefix(fn, SRCDIR "/chart2/source/view/main/PropertyMapper.cxx")
+ || loplugin::hasPathnamePrefix(fn, SRCDIR "/sc/source/core/data/formulacell.cxx"))
+ return;
+ TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+ }
+
+ bool VisitBinaryOperator(BinaryOperator const*);
+ bool VisitCXXOperatorCallExpr(CXXOperatorCallExpr const*);
+ bool TraverseStaticAssertDecl(StaticAssertDecl*);
+
+private:
+ // note, abusing std::unique_ptr as a std::optional lookalike
+ std::unique_ptr<APSInt> getExprValue(const Expr* arg);
+};
+
+bool ExpressionAlwaysZero::VisitBinaryOperator(BinaryOperator const* binaryOperator)
+{
+ if (ignoreLocation(binaryOperator))
+ return true;
+ if (binaryOperator->getBeginLoc().isMacroID())
+ return true;
+
+ auto op = binaryOperator->getOpcode();
+ if (!(op == BO_And || op == BO_AndAssign || op == BO_LAnd))
+ return true;
+
+ auto lhsValue = getExprValue(binaryOperator->getLHS());
+ auto rhsValue = getExprValue(binaryOperator->getRHS());
+ if (lhsValue && lhsValue->getExtValue() == 0)
+ ; // ok
+ else if (rhsValue && rhsValue->getExtValue() == 0)
+ ; // ok
+ else if (lhsValue && rhsValue && (lhsValue->getExtValue() & rhsValue->getExtValue()) == 0)
+ ; // ok
+ else
+ return true;
+ report(DiagnosticsEngine::Warning, "expression always evaluates to zero, lhs=%0 rhs=%1",
+ binaryOperator->getBeginLoc())
+ << (lhsValue ? compat::toString(*lhsValue, 10) : "unknown")
+ << (rhsValue ? compat::toString(*rhsValue, 10) : "unknown")
+ << binaryOperator->getSourceRange();
+ return true;
+}
+
+bool ExpressionAlwaysZero::VisitCXXOperatorCallExpr(CXXOperatorCallExpr const* cxxOperatorCallExpr)
+{
+ if (ignoreLocation(cxxOperatorCallExpr))
+ return true;
+ if (cxxOperatorCallExpr->getBeginLoc().isMacroID())
+ return true;
+
+ auto op = cxxOperatorCallExpr->getOperator();
+ if (!(op == OO_Amp || op == OO_AmpEqual || op == OO_AmpAmp))
+ return true;
+
+ if (cxxOperatorCallExpr->getNumArgs() != 2)
+ return true;
+ auto lhsValue = getExprValue(cxxOperatorCallExpr->getArg(0));
+ auto rhsValue = getExprValue(cxxOperatorCallExpr->getArg(1));
+ if (lhsValue && lhsValue->getExtValue() == 0)
+ ; // ok
+ else if (rhsValue && rhsValue->getExtValue() == 0)
+ ; // ok
+ else if (lhsValue && rhsValue && (lhsValue->getExtValue() & rhsValue->getExtValue()) == 0)
+ ; // ok
+ else
+ return true;
+ report(DiagnosticsEngine::Warning, "expression always evaluates to zero, lhs=%0 rhs=%1",
+ cxxOperatorCallExpr->getBeginLoc())
+ << (lhsValue ? compat::toString(*lhsValue, 10) : "unknown")
+ << (rhsValue ? compat::toString(*rhsValue, 10) : "unknown")
+ << cxxOperatorCallExpr->getSourceRange();
+ return true;
+}
+
+std::unique_ptr<APSInt> ExpressionAlwaysZero::getExprValue(Expr const* expr)
+{
+ expr = expr->IgnoreParenCasts();
+ // ignore this, it seems to trigger an infinite recursion
+ if (isa<UnaryExprOrTypeTraitExpr>(expr))
+ {
+ return std::unique_ptr<APSInt>();
+ }
+ APSInt x1;
+ if (!expr->isValueDependent() && compat::EvaluateAsInt(expr, x1, compiler.getASTContext()))
+ return std::unique_ptr<APSInt>(new APSInt(x1));
+ return std::unique_ptr<APSInt>();
+}
+
+// these will often evaluate to zero harmlessly
+bool ExpressionAlwaysZero::TraverseStaticAssertDecl(StaticAssertDecl*) { return true; }
+
+loplugin::Plugin::Registration<ExpressionAlwaysZero> X("expressionalwayszero", false);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */