new plugin constparams

very basic detection of pointer and reference params that can be const.

Off by default until the relevant changes have landed.

Change-Id: I88bba4e67307e3fb0e11dad252ec59c913828763

1 files changed, 407 insertions, 0 deletions

diff --git a/compilerplugins/clang/constparams.cxx b/compilerplugins/clang/constparams.cxx
new file mode 100644
index 000000000000..291a4e7db4d2
--- /dev/null
+++ b/compilerplugins/clang/constparams.cxx
@@ -0,0 +1,407 @@
+/* -*- 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 "plugin.hxx"
+#include "compat.hxx"
+#include "check.hxx"
+
+/**
+   Find pointer and reference params that can be declared const.
+
+   This is not a sophisticated analysis. It deliberately skips all of the hard cases for now.
+   It is an exercise in getting the most benefit for the least effort.
+*/
+namespace
+{
+
+class ConstParams:
+    public RecursiveASTVisitor<ConstParams>, public loplugin::Plugin
+{
+public:
+    explicit ConstParams(InstantiationData const & data): Plugin(data) {}
+
+    virtual void run() override {
+        TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
+    }
+
+    bool VisitFunctionDecl(FunctionDecl *);
+    bool VisitDeclRefExpr( const DeclRefExpr* );
+private:
+    bool checkIfCanBeConst(const Stmt*);
+    bool isPointerOrReferenceToConst(const QualType& qt);
+    StringRef getFilename(const SourceLocation& loc);
+
+    bool mbInsideFunction;
+    std::set<const ParmVarDecl*> interestingSet;
+    std::set<const ParmVarDecl*> cannotBeConstSet;
+};
+
+bool ConstParams::VisitFunctionDecl(FunctionDecl * functionDecl)
+{
+    if (ignoreLocation(functionDecl) || !functionDecl->doesThisDeclarationHaveABody()) {
+        return true;
+    }
+    // ignore stuff that forms part of the stable URE interface
+    if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(
+                              functionDecl->getCanonicalDecl()->getNameInfo().getLoc()))) {
+        return true;
+    }
+    // TODO ignore these for now, requires some extra work
+    if (isa<CXXConstructorDecl>(functionDecl)) {
+        return true;
+    }
+    // TODO ignore template stuff for now
+    if (functionDecl->getTemplatedKind() != FunctionDecl::TK_NonTemplate) {
+        return true;
+    }
+    if (isa<CXXMethodDecl>(functionDecl)
+        && dyn_cast<CXXMethodDecl>(functionDecl)->getParent()->getDescribedClassTemplate() != nullptr ) {
+        return true;
+    }
+    // ignore virtual methods
+    if (isa<CXXMethodDecl>(functionDecl)
+        && dyn_cast<CXXMethodDecl>(functionDecl)->isVirtual() ) {
+        return true;
+    }
+    // ignore C main
+    if (functionDecl->isMain()) {
+        return true;
+    }
+    // ignore macro expansions so we can ignore the IMPL_LINK macros from include/tools/link.hxx
+    // TODO make this more precise
+    if (functionDecl->getLocation().isMacroID())
+        return true;
+
+    if (functionDecl->getIdentifier()) {
+        StringRef name = functionDecl->getName();
+        if (name == "yyerror" // ignore lex/yacc callback
+                // some function callbacks
+            || name == "PDFSigningPKCS7PasswordCallback"
+            || name == "VCLExceptionSignal_impl"
+            || name == "parseXcsFile"
+                // UNO component entry points
+            || name.endswith("component_getFactory"))
+                return true;
+    }
+
+    StringRef aFileName = getFilename(functionDecl->getLocStart());
+    if (aFileName.startswith(SRCDIR "/sal/")
+        || aFileName.startswith(SRCDIR "/bridges/")
+        || aFileName.startswith(SRCDIR "/binaryurp/")
+        || aFileName.startswith(SRCDIR "/stoc/")
+        || aFileName.startswith(WORKDIR "/YaccTarget/unoidl/source/sourceprovider-parser.cxx")
+        // some weird calling through a function pointer
+        || aFileName.startswith(SRCDIR "/svtools/source/table/defaultinputhandler.cxx")
+        // windows only
+        || aFileName.startswith(SRCDIR "/basic/source/sbx/sbxdec.cxx")
+        || aFileName.startswith(SRCDIR "/sfx2/source/doc/syspath.cxx")) {
+        return true;
+    }
+
+    // calculate the ones we want to check
+    interestingSet.clear();
+    for (const ParmVarDecl *pParmVarDecl : compat::parameters(*functionDecl)) {
+        // ignore unused params
+        if (pParmVarDecl->getName().empty())
+            continue;
+        auto const type = loplugin::TypeCheck(pParmVarDecl->getType());
+        if (!type.Pointer() && !type.LvalueReference())
+            continue;
+        if (type.Pointer().Const())
+            continue;
+        if (type.LvalueReference().Const())
+            continue;
+        // since we can't normally change typedefs, just ignore them
+        if (isa<TypedefType>(pParmVarDecl->getType()))
+            continue;
+        // TODO ignore these for now, has some effects I don't understand
+        if (type.Pointer().Pointer())
+            continue;
+        // const is meaningless when applied to function pointer types
+        if (pParmVarDecl->getType()->isFunctionPointerType())
+            continue;
+        interestingSet.insert(pParmVarDecl);
+    }
+    if (interestingSet.empty()) {
+        return true;
+    }
+
+    mbInsideFunction = true;
+    cannotBeConstSet.clear();
+    bool ret = RecursiveASTVisitor::TraverseStmt(functionDecl->getBody());
+    mbInsideFunction = false;
+
+    for (const ParmVarDecl *pParmVarDecl : interestingSet) {
+        if (cannotBeConstSet.find(pParmVarDecl) == cannotBeConstSet.end()) {
+            report(
+                DiagnosticsEngine::Warning,
+                "this parameter can be const",
+                pParmVarDecl->getLocStart())
+                << pParmVarDecl->getSourceRange();
+            if (functionDecl->getCanonicalDecl()->getLocation() != functionDecl->getLocation()) {
+                unsigned idx = pParmVarDecl->getFunctionScopeIndex();
+                ParmVarDecl* pOther = functionDecl->getCanonicalDecl()->getParamDecl(idx);
+                report(
+                    DiagnosticsEngine::Note,
+                    "canonical parameter declaration here",
+                    pOther->getLocStart())
+                    << pOther->getSourceRange();
+            }
+            //functionDecl->dump();
+        }
+    }
+    return ret;
+}
+
+bool ConstParams::VisitDeclRefExpr( const DeclRefExpr* declRefExpr )
+{
+    if (!mbInsideFunction) {
+        return true;
+    }
+    const ParmVarDecl* parmVarDecl = dyn_cast_or_null<ParmVarDecl>(declRefExpr->getDecl());
+    if (!parmVarDecl) {
+        return true;
+    }
+    if (interestingSet.find(parmVarDecl) == interestingSet.end()) {
+        return true;
+    }
+    if (!checkIfCanBeConst(declRefExpr))
+        cannotBeConstSet.insert(parmVarDecl);
+
+    return true;
+}
+
+bool ConstParams::checkIfCanBeConst(const Stmt* stmt)
+{
+    const Stmt* parent = parentStmt( stmt );
+    if (isa<UnaryOperator>(parent)) {
+        const UnaryOperator* unaryOperator = dyn_cast<UnaryOperator>(parent);
+        UnaryOperator::Opcode op = unaryOperator->getOpcode();
+        if (op == UO_AddrOf || op == UO_PreInc || op == UO_PostInc
+            || op == UO_PreDec || op == UO_PostDec) {
+            return false;
+        }
+        if (op == UO_Deref) {
+            return checkIfCanBeConst(parent);
+        }
+        return true;
+    } else if (isa<BinaryOperator>(parent)) {
+        const BinaryOperator* binaryOp = dyn_cast<BinaryOperator>(parent);
+        BinaryOperator::Opcode op = binaryOp->getOpcode();
+        // TODO could do better, but would require tracking the LHS
+        if (binaryOp->getRHS() == stmt && op == BO_Assign) {
+            return false;
+        }
+        if (binaryOp->getRHS() == stmt) {
+            return true;
+        }
+        if (op == BO_Assign || op == BO_PtrMemD || op == BO_PtrMemI || op == BO_MulAssign
+            || op == BO_DivAssign || op == BO_RemAssign || op == BO_AddAssign
+            || op == BO_SubAssign || op == BO_ShlAssign || op == BO_ShrAssign
+            || op == BO_AndAssign || op == BO_XorAssign || op == BO_OrAssign) {
+            return false;
+        }
+        // for pointer arithmetic need to check parent
+        if (binaryOp->getType()->isPointerType()) {
+            return checkIfCanBeConst(parent);
+        }
+        return true;
+    } else if (isa<CXXConstructExpr>(parent)) {
+        const CXXConstructExpr* constructExpr = dyn_cast<CXXConstructExpr>(parent);
+        const CXXConstructorDecl * constructorDecl = constructExpr->getConstructor();
+        for (unsigned i = 0; i < constructExpr->getNumArgs(); ++i) {
+            if (constructExpr->getArg(i) == stmt) {
+                return isPointerOrReferenceToConst(constructorDecl->getParamDecl(i)->getType());
+            }
+        }
+        std::cout << "dump0" << std::endl;
+        parent->dump();
+    } else if (isa<CXXOperatorCallExpr>(parent)) {
+        const CXXOperatorCallExpr* operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(parent);
+        const CXXMethodDecl* calleeMethodDecl = dyn_cast<CXXMethodDecl>(operatorCallExpr->getDirectCallee());
+        if (calleeMethodDecl) {
+            // unary operator
+            if (calleeMethodDecl->getNumParams() == 0) {
+                return calleeMethodDecl->isConst();
+            }
+            // binary operator
+            if (operatorCallExpr->getArg(0) == stmt) {
+                return calleeMethodDecl->isConst();
+            }
+            if (operatorCallExpr->getArg(1) == stmt) {
+                return isPointerOrReferenceToConst(calleeMethodDecl->getParamDecl(0)->getType());
+            }
+        } else {
+            const Expr* callee = operatorCallExpr->getCallee()->IgnoreParenImpCasts();
+            const DeclRefExpr* dr = dyn_cast<DeclRefExpr>(callee);
+            const FunctionDecl* calleeFunctionDecl = nullptr;
+            if (dr) {
+                calleeFunctionDecl = dyn_cast<FunctionDecl>(dr->getDecl());
+            }
+            if (calleeFunctionDecl) {
+                for (unsigned i = 0; i < operatorCallExpr->getNumArgs(); ++i) {
+                    if (operatorCallExpr->getArg(i) == stmt) {
+                        return isPointerOrReferenceToConst(calleeFunctionDecl->getParamDecl(i)->getType());
+                    }
+                }
+            }
+        }
+        std::cout << "dump1" << std::endl;
+        parent->dump();
+        stmt->dump();
+    } else if (isa<CallExpr>(parent)) {
+        const CallExpr* callExpr = dyn_cast<CallExpr>(parent);
+        QualType functionType = callExpr->getCallee()->getType();
+        if (functionType->isFunctionPointerType()) {
+            functionType = functionType->getPointeeType();
+        }
+        if (const FunctionProtoType* prototype = functionType->getAs<FunctionProtoType>()) {
+            // TODO could do better
+            if (prototype->isVariadic()) {
+                return false;
+            }
+            if (callExpr->getCallee() == stmt) {
+                return true;
+            }
+            for (unsigned i = 0; i < callExpr->getNumArgs(); ++i) {
+                if (callExpr->getArg(i) == stmt) {
+                    return isPointerOrReferenceToConst(prototype->getParamType(i));
+                }
+            }
+        }
+        const FunctionDecl* calleeFunctionDecl = callExpr->getDirectCallee();
+        if (isa<CXXMemberCallExpr>(parent)) {
+            const CXXMemberCallExpr* memberCallExpr = dyn_cast<CXXMemberCallExpr>(parent);
+            const MemberExpr* memberExpr = dyn_cast<MemberExpr>(stmt);
+            if (memberExpr && memberCallExpr->getImplicitObjectArgument() == memberExpr->getBase())
+            {
+                const CXXMethodDecl* calleeMethodDecl = dyn_cast<CXXMethodDecl>(calleeFunctionDecl);
+                return calleeMethodDecl->isConst();
+            }
+        }
+        if (!calleeFunctionDecl) {
+            std::cout << "---------------dump2" << std::endl;
+            std::cout << "parent" << std::endl;
+            parent->dump();
+            std::cout << "child" << std::endl;
+            stmt->dump();
+            std::cout << "callee-type" << std::endl;
+            callExpr->getCallee()->getType()->dump();
+            for (unsigned i = 0; i < callExpr->getNumArgs(); ++i) {
+                std::cout << "    param " << i << std::endl;
+                callExpr->getArg(i)->dump();
+            }
+            return true;
+        }
+        // TODO could do better
+        if (calleeFunctionDecl->isVariadic()) {
+            return false;
+        }
+        if (callExpr->getCallee() == stmt) {
+            return true;
+        }
+        for (unsigned i = 0; i < callExpr->getNumArgs(); ++i) {
+            if (i >= calleeFunctionDecl->getNumParams()) // can happen in template code
+                break;
+            if (callExpr->getArg(i) == stmt) {
+                return isPointerOrReferenceToConst(calleeFunctionDecl->getParamDecl(i)->getType());
+            }
+        }
+        std::cout << "------------dump3" << std::endl;
+        std::cout << "parent" << std::endl;
+        parent->dump();
+        std::cout << "child" << std::endl;
+        stmt->dump();
+        calleeFunctionDecl->dump();
+        for (unsigned i = 0; i < callExpr->getNumArgs(); ++i) {
+            std::cout << "    param " << i << std::endl;
+            callExpr->getArg(i)->dump();
+        }
+        if (isa<CXXMemberCallExpr>(parent)) {
+            std::cout << "implicit" << std::endl;
+            dyn_cast<CXXMemberCallExpr>(parent)->getImplicitObjectArgument()->dump();
+        }
+    } else if (isa<CXXReinterpretCastExpr>(parent)) {
+        return false;
+    } else if (isa<CXXConstCastExpr>(parent)) {
+        return false;
+    } else if (isa<CastExpr>(parent)) { // all other cast expression subtypes
+        return checkIfCanBeConst(parent);
+    } else if (isa<MemberExpr>(parent)) {
+        return checkIfCanBeConst(parent);
+    } else if (isa<ArraySubscriptExpr>(parent)) {
+        return checkIfCanBeConst(parent);
+    } else if (isa<ParenExpr>(parent)) {
+        return checkIfCanBeConst(parent);
+    } else if (isa<DeclStmt>(parent)) {
+        // TODO could do better here, but would require tracking the target(s)
+        return false;
+    } else if (isa<ReturnStmt>(parent)) {
+        return isPointerOrReferenceToConst(dyn_cast<Expr>(stmt)->getType());
+    } else if (isa<InitListExpr>(parent)) {
+        return false;
+    } else if (isa<IfStmt>(parent)) {
+        return true;
+    } else if (isa<WhileStmt>(parent)) {
+        return true;
+    } else if (isa<ForStmt>(parent)) {
+        return true;
+    } else if (isa<CompoundStmt>(parent)) {
+        return true;
+    } else if (isa<SwitchStmt>(parent)) {
+        return true;
+    } else if (isa<CXXDeleteExpr>(parent)) {
+        return false;
+    } else if (isa<VAArgExpr>(parent)) {
+        return false;
+    } else if (isa<MaterializeTemporaryExpr>(parent)) {
+        return true;
+    } else if (const ConditionalOperator* conditionalExpr = dyn_cast<ConditionalOperator>(parent)) {
+        if (conditionalExpr->getCond() == stmt)
+            return true;
+        return checkIfCanBeConst(parent);
+    } else {
+        std::cout << "dump5" << std::endl;
+        parent->dump();
+    }
+    return true;
+}
+
+bool ConstParams::isPointerOrReferenceToConst(const QualType& qt) {
+    auto const type = loplugin::TypeCheck(qt);
+    if (type.Pointer()) {
+        return bool(type.Pointer().Const());
+    } else if (type.LvalueReference().Const().Pointer()) {
+        // If we have a method that takes (T* t) and it calls std::vector<T*>::push_back
+        // then the type of push_back is T * const &
+        // There is probably a more elegant way to check this, but it will probably require
+        // recalculating types while walking up the AST.
+        return false;
+    } else if (type.LvalueReference()) {
+        return bool(type.LvalueReference().Const());
+    }
+    return false;
+}
+
+StringRef ConstParams::getFilename(const SourceLocation& loc)
+{
+    SourceLocation spellingLocation = compiler.getSourceManager().getSpellingLoc(loc);
+    StringRef name { compiler.getSourceManager().getFilename(spellingLocation) };
+    return name;
+}
+
+loplugin::Plugin::Registration< ConstParams > X("constparams", false);
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */