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office-gobmx/compilerplugins/clang/unusedvarsglobal.cxx
Noel Grandin f2517e8290 improve loplugin:unusedvarsglobal 
to find any global variable, was checking the wrong property of
VarDecl

Change-Id: I454b4e0c1701bb0771768a1ee10cd738c4ab0726
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102278
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
2020-09-09 08:25:30 +02:00

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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/.
*/
#if !defined _WIN32 //TODO, #include <sys/file.h>
#include <cassert>
#include <string>
#include <iostream>
#include <fstream>
#include <unordered_set>
#include <vector>
#include <algorithm>
#include <sys/file.h>
#include <unistd.h>
#include "config_clang.h"
#include "plugin.hxx"
#include "compat.hxx"
#include "check.hxx"
#if CLANG_VERSION >= 110000
#include "clang/AST/ParentMapContext.h"
#endif
/**
This performs two analyses:
(1) look for unused global vars
(2) look for global vars that are write-only
*/
namespace
{
struct MyVarInfo
{
const VarDecl* varDecl;
std::string fieldName;
std::string fieldType;
std::string sourceLocation;
};
bool operator<(const MyVarInfo& lhs, const MyVarInfo& rhs)
{
return std::tie(lhs.sourceLocation, lhs.fieldName)
< std::tie(rhs.sourceLocation, rhs.fieldName);
}
// try to limit the voluminous output a little
static std::set<MyVarInfo> readFromSet;
static std::set<MyVarInfo> writeToSet;
static std::set<MyVarInfo> definitionSet;
/**
* Wrap the different kinds of callable and callee objects in the clang AST so I can define methods that handle everything.
*/
class CallerWrapper
{
const CallExpr* m_callExpr;
const CXXConstructExpr* m_cxxConstructExpr;
public:
CallerWrapper(const CallExpr* callExpr)
: m_callExpr(callExpr)
, m_cxxConstructExpr(nullptr)
{
}
CallerWrapper(const CXXConstructExpr* cxxConstructExpr)
: m_callExpr(nullptr)
, m_cxxConstructExpr(cxxConstructExpr)
{
}
unsigned getNumArgs() const
{
return m_callExpr ? m_callExpr->getNumArgs() : m_cxxConstructExpr->getNumArgs();
}
const Expr* getArg(unsigned i) const
{
return m_callExpr ? m_callExpr->getArg(i) : m_cxxConstructExpr->getArg(i);
}
};
class CalleeWrapper
{
const FunctionDecl* m_calleeFunctionDecl = nullptr;
const CXXConstructorDecl* m_cxxConstructorDecl = nullptr;
const FunctionProtoType* m_functionPrototype = nullptr;
public:
explicit CalleeWrapper(const FunctionDecl* calleeFunctionDecl)
: m_calleeFunctionDecl(calleeFunctionDecl)
{
}
explicit CalleeWrapper(const CXXConstructExpr* cxxConstructExpr)
: m_cxxConstructorDecl(cxxConstructExpr->getConstructor())
{
}
explicit CalleeWrapper(const FunctionProtoType* functionPrototype)
: m_functionPrototype(functionPrototype)
{
}
unsigned getNumParams() const
{
if (m_calleeFunctionDecl)
return m_calleeFunctionDecl->getNumParams();
else if (m_cxxConstructorDecl)
return m_cxxConstructorDecl->getNumParams();
else if (m_functionPrototype->param_type_begin() == m_functionPrototype->param_type_end())
// FunctionProtoType will assert if we call getParamTypes() and it has no params
return 0;
else
return m_functionPrototype->getParamTypes().size();
}
const QualType getParamType(unsigned i) const
{
if (m_calleeFunctionDecl)
return m_calleeFunctionDecl->getParamDecl(i)->getType();
else if (m_cxxConstructorDecl)
return m_cxxConstructorDecl->getParamDecl(i)->getType();
else
return m_functionPrototype->getParamTypes()[i];
}
std::string getNameAsString() const
{
if (m_calleeFunctionDecl)
return m_calleeFunctionDecl->getNameAsString();
else if (m_cxxConstructorDecl)
return m_cxxConstructorDecl->getNameAsString();
else
return "";
}
CXXMethodDecl const* getAsCXXMethodDecl() const
{
if (m_calleeFunctionDecl)
return dyn_cast<CXXMethodDecl>(m_calleeFunctionDecl);
return nullptr;
}
};
class UnusedVarsGlobal : public loplugin::FilteringPlugin<UnusedVarsGlobal>
{
public:
explicit UnusedVarsGlobal(loplugin::InstantiationData const& data)
: FilteringPlugin(data)
{
}
virtual void run() override;
bool shouldVisitTemplateInstantiations() const { return true; }
bool shouldVisitImplicitCode() const { return true; }
bool VisitVarDecl(const VarDecl*);
bool VisitDeclRefExpr(const DeclRefExpr*);
bool TraverseCXXMethodDecl(CXXMethodDecl*);
bool TraverseFunctionDecl(FunctionDecl*);
bool TraverseIfStmt(IfStmt*);
private:
MyVarInfo niceName(const VarDecl*);
void checkIfReadFrom(const VarDecl* fieldDecl, const DeclRefExpr* declRefExpr);
void checkIfWrittenTo(const VarDecl* fieldDecl, const DeclRefExpr* declRefExpr);
bool isSomeKindOfZero(const Expr* arg);
bool checkForWriteWhenUsingCollectionType(const CXXMethodDecl* calleeMethodDecl);
bool IsPassedByNonConst(const VarDecl* fieldDecl, const Stmt* child, CallerWrapper callExpr,
CalleeWrapper calleeFunctionDecl);
llvm::Optional<CalleeWrapper> getCallee(CallExpr const*);
// For reasons I do not understand, parentFunctionDecl() is not reliable, so
// we store the parent function on the way down the AST.
FunctionDecl* insideFunctionDecl = nullptr;
std::vector<VarDecl const*> insideConditionalCheckOfVarSet;
};
void UnusedVarsGlobal::run()
{
TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
if (!isUnitTestMode())
{
// dump all our output in one write call - this is to try and limit IO "crosstalk" between multiple processes
// writing to the same logfile
std::string output;
for (const MyVarInfo& s : readFromSet)
output += "read:\t" + s.sourceLocation + "\t" + s.fieldName + "\n";
for (const MyVarInfo& s : writeToSet)
output += "write:\t" + s.sourceLocation + "\t" + s.fieldName + "\n";
for (const MyVarInfo& s : definitionSet)
output += "definition:\t" + s.fieldName + "\t" + s.fieldType + "\t" + s.sourceLocation
+ "\n";
std::ofstream myfile;
myfile.open(WORKDIR "/loplugin.unusedvarsglobal.log", std::ios::app | std::ios::out);
myfile << output;
myfile.close();
}
else
{
for (const MyVarInfo& s : readFromSet)
report(DiagnosticsEngine::Warning, "read", compat::getBeginLoc(s.varDecl));
for (const MyVarInfo& s : writeToSet)
report(DiagnosticsEngine::Warning, "write", compat::getBeginLoc(s.varDecl));
}
}
MyVarInfo UnusedVarsGlobal::niceName(const VarDecl* varDecl)
{
MyVarInfo aInfo;
aInfo.varDecl = varDecl;
aInfo.fieldName = varDecl->getNameAsString();
// sometimes the name (if it's an anonymous thing) contains the full path of the build folder, which we don't need
size_t idx = aInfo.fieldName.find(SRCDIR);
if (idx != std::string::npos)
{
aInfo.fieldName = aInfo.fieldName.replace(idx, strlen(SRCDIR), "");
}
aInfo.fieldType = varDecl->getType().getAsString();
SourceLocation expansionLoc
= compiler.getSourceManager().getExpansionLoc(varDecl->getLocation());
StringRef name = getFilenameOfLocation(expansionLoc);
aInfo.sourceLocation
= std::string(name.substr(strlen(SRCDIR) + 1)) + ":"
+ std::to_string(compiler.getSourceManager().getSpellingLineNumber(expansionLoc));
loplugin::normalizeDotDotInFilePath(aInfo.sourceLocation);
return aInfo;
}
bool UnusedVarsGlobal::VisitVarDecl(const VarDecl* varDecl)
{
varDecl = varDecl->getCanonicalDecl();
if (isa<ParmVarDecl>(varDecl))
return true;
if (!varDecl->hasGlobalStorage())
return true;
if (!varDecl->getLocation().isValid() || ignoreLocation(varDecl))
return true;
// ignore stuff that forms part of the stable URE interface
if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(varDecl->getLocation())))
return true;
/**
If we have
const size_t NB_PRODUCTS = 3;
int DefaultProductDir[NB_PRODUCTS] = { 3, 3, 3 };
clang will inline the constant "3" and never tell us that we are reading from NB_PRODUCTS,
so just ignore integer constants.
*/
auto varType = varDecl->getType();
if (varType.isConstQualified() && varType->isIntegerType())
return true;
auto initExpr = varDecl->getAnyInitializer();
if (initExpr && !isSomeKindOfZero(initExpr))
writeToSet.insert(niceName(varDecl));
definitionSet.insert(niceName(varDecl));
return true;
}
bool UnusedVarsGlobal::VisitDeclRefExpr(const DeclRefExpr* declRefExpr)
{
const Decl* decl = declRefExpr->getDecl();
const VarDecl* varDecl = dyn_cast<VarDecl>(decl);
if (!varDecl)
return true;
if (isa<ParmVarDecl>(varDecl))
return true;
if (!varDecl->hasGlobalStorage())
return true;
varDecl = varDecl->getCanonicalDecl();
if (!varDecl->getLocation().isValid() || ignoreLocation(varDecl))
return true;
// ignore stuff that forms part of the stable URE interface
if (isInUnoIncludeFile(compiler.getSourceManager().getSpellingLoc(varDecl->getLocation())))
return true;
checkIfReadFrom(varDecl, declRefExpr);
checkIfWrittenTo(varDecl, declRefExpr);
return true;
}
/**
Does the expression being used to initialise a field value evaluate to
the same as a default value?
*/
bool UnusedVarsGlobal::isSomeKindOfZero(const Expr* arg)
{
assert(arg);
if (arg->isValueDependent())
return false;
if (arg->getType().isNull())
return false;
if (isa<CXXDefaultArgExpr>(arg))
arg = dyn_cast<CXXDefaultArgExpr>(arg)->getExpr();
arg = arg->IgnoreParenCasts();
// ignore this, it seems to trigger an infinite recursion
if (isa<UnaryExprOrTypeTraitExpr>(arg))
return false;
if (auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(arg))
return cxxConstructExpr->getConstructor()->isDefaultConstructor();
APSInt x1;
if (compat::EvaluateAsInt(arg, x1, compiler.getASTContext()))
return x1 == 0;
if (isa<CXXNullPtrLiteralExpr>(arg))
return true;
if (isa<MaterializeTemporaryExpr>(arg))
{
const CXXBindTemporaryExpr* strippedArg
= dyn_cast_or_null<CXXBindTemporaryExpr>(arg->IgnoreParenCasts());
if (strippedArg)
{
auto temp = dyn_cast<CXXTemporaryObjectExpr>(strippedArg->getSubExpr());
if (temp->getNumArgs() == 0)
{
if (loplugin::TypeCheck(temp->getType())
.Class("OUString")
.Namespace("rtl")
.GlobalNamespace())
return true;
if (loplugin::TypeCheck(temp->getType())
.Class("OString")
.Namespace("rtl")
.GlobalNamespace())
return true;
return false;
}
}
}
// Get the expression contents.
// This helps us find params which are always initialised with something like "OUString()".
SourceManager& SM = compiler.getSourceManager();
SourceLocation startLoc = compat::getBeginLoc(arg);
SourceLocation endLoc = compat::getEndLoc(arg);
const char* p1 = SM.getCharacterData(startLoc);
const char* p2 = SM.getCharacterData(endLoc);
if (!p1 || !p2 || (p2 - p1) < 0 || (p2 - p1) > 40)
return false;
unsigned n = Lexer::MeasureTokenLength(endLoc, SM, compiler.getLangOpts());
std::string s(p1, p2 - p1 + n);
// strip linefeed and tab characters so they don't interfere with the parsing of the log file
std::replace(s.begin(), s.end(), '\r', ' ');
std::replace(s.begin(), s.end(), '\n', ' ');
std::replace(s.begin(), s.end(), '\t', ' ');
// now normalize the value. For some params, like OUString, we can pass it as OUString() or "" and they are the same thing
if (s == "OUString()")
return true;
else if (s == "OString()")
return true;
else if (s == "aEmptyOUStr") //sw
return true;
else if (s == "EMPTY_OUSTRING") //sc
return true;
else if (s == "GetEmptyOUString()") //sc
return true;
return false;
}
static char easytolower(char in)
{
if (in <= 'Z' && in >= 'A')
return in - ('Z' - 'z');
return in;
}
bool startswith(const std::string& rStr, const char* pSubStr)
{
return rStr.compare(0, strlen(pSubStr), pSubStr) == 0;
}
bool UnusedVarsGlobal::TraverseCXXMethodDecl(CXXMethodDecl* cxxMethodDecl)
{
auto copy2 = insideFunctionDecl;
insideFunctionDecl = cxxMethodDecl;
bool ret = RecursiveASTVisitor::TraverseCXXMethodDecl(cxxMethodDecl);
insideFunctionDecl = copy2;
return ret;
}
bool UnusedVarsGlobal::TraverseFunctionDecl(FunctionDecl* functionDecl)
{
auto copy2 = insideFunctionDecl;
insideFunctionDecl = functionDecl;
bool ret = RecursiveASTVisitor::TraverseFunctionDecl(functionDecl);
insideFunctionDecl = copy2;
return ret;
}
bool UnusedVarsGlobal::TraverseIfStmt(IfStmt* ifStmt)
{
VarDecl const* varDecl = nullptr;
Expr const* cond = ifStmt->getCond()->IgnoreParenImpCasts();
if (auto memberCallExpr = dyn_cast<CXXMemberCallExpr>(cond))
{
if (auto cxxConvert = dyn_cast_or_null<CXXConversionDecl>(memberCallExpr->getMethodDecl()))
{
if (cxxConvert->getConversionType()->isBooleanType())
if (auto declRefExpr = dyn_cast<DeclRefExpr>(
memberCallExpr->getImplicitObjectArgument()->IgnoreParenImpCasts()))
if ((varDecl = dyn_cast<VarDecl>(declRefExpr->getDecl())))
insideConditionalCheckOfVarSet.push_back(varDecl);
}
}
else if (auto declRefExpr = dyn_cast<DeclRefExpr>(cond))
{
if ((varDecl = dyn_cast<VarDecl>(declRefExpr->getDecl())))
insideConditionalCheckOfVarSet.push_back(varDecl);
}
bool ret = RecursiveASTVisitor::TraverseIfStmt(ifStmt);
if (varDecl)
insideConditionalCheckOfVarSet.pop_back();
return ret;
}
void UnusedVarsGlobal::checkIfReadFrom(const VarDecl* varDecl, const DeclRefExpr* declRefExpr)
{
auto parentsRange = compiler.getASTContext().getParents(*declRefExpr);
const Stmt* child = declRefExpr;
const Stmt* parent
= parentsRange.begin() == parentsRange.end() ? nullptr : parentsRange.begin()->get<Stmt>();
// walk up the tree until we find something interesting
bool bPotentiallyReadFrom = false;
bool bDump = false;
auto walkUp = [&]() {
child = parent;
auto parentsRange = compiler.getASTContext().getParents(*parent);
parent = parentsRange.begin() == parentsRange.end() ? nullptr
: parentsRange.begin()->get<Stmt>();
};
do
{
if (!parent)
{
// check if we're inside a CXXCtorInitializer or a VarDecl
auto parentsRange = compiler.getASTContext().getParents(*child);
if (parentsRange.begin() != parentsRange.end())
{
const Decl* decl = parentsRange.begin()->get<Decl>();
if (decl && (isa<CXXConstructorDecl>(decl) || isa<VarDecl>(decl)))
bPotentiallyReadFrom = true;
}
if (!bPotentiallyReadFrom)
return;
break;
}
if (isa<CXXReinterpretCastExpr>(parent))
{
// once we see one of these, there is not much useful we can know
bPotentiallyReadFrom = true;
break;
}
else if (isa<CastExpr>(parent) || isa<MemberExpr>(parent) || isa<ParenExpr>(parent)
|| isa<ParenListExpr>(parent) || isa<ArrayInitLoopExpr>(parent)
|| isa<ExprWithCleanups>(parent))
{
walkUp();
}
else if (auto unaryOperator = dyn_cast<UnaryOperator>(parent))
{
UnaryOperator::Opcode op = unaryOperator->getOpcode();
if (declRefExpr->getType()->isArrayType() && op == UO_Deref)
{
// ignore, deref'ing an array does not count as a read
}
else if (op == UO_AddrOf || op == UO_Deref || op == UO_Plus || op == UO_Minus
|| op == UO_Not || op == UO_LNot)
{
bPotentiallyReadFrom = true;
break;
}
/* The following are technically reads, but from a code-sense they're more of a write/modify, so
ignore them to find interesting fields that only modified, not usefully read:
UO_PreInc / UO_PostInc / UO_PreDec / UO_PostDec
But we still walk up in case the result of the expression is used in a read sense.
*/
walkUp();
}
else if (auto caseStmt = dyn_cast<CaseStmt>(parent))
{
bPotentiallyReadFrom = caseStmt->getLHS() == child || caseStmt->getRHS() == child;
break;
}
else if (auto ifStmt = dyn_cast<IfStmt>(parent))
{
bPotentiallyReadFrom = ifStmt->getCond() == child;
break;
}
else if (auto doStmt = dyn_cast<DoStmt>(parent))
{
bPotentiallyReadFrom = doStmt->getCond() == child;
break;
}
else if (auto arraySubscriptExpr = dyn_cast<ArraySubscriptExpr>(parent))
{
if (arraySubscriptExpr->getIdx() == child)
{
bPotentiallyReadFrom = true;
break;
}
walkUp();
}
else if (auto binaryOp = dyn_cast<BinaryOperator>(parent))
{
BinaryOperator::Opcode op = binaryOp->getOpcode();
const bool assignmentOp = op == BO_Assign || 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;
if (binaryOp->getLHS() == child && assignmentOp)
break;
else
{
bPotentiallyReadFrom = true;
break;
}
}
else if (auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(parent))
{
auto op = operatorCallExpr->getOperator();
const bool assignmentOp = op == OO_Equal || op == OO_StarEqual || op == OO_SlashEqual
|| op == OO_PercentEqual || op == OO_PlusEqual
|| op == OO_MinusEqual || op == OO_LessLessEqual
|| op == OO_AmpEqual || op == OO_CaretEqual
|| op == OO_PipeEqual;
if (operatorCallExpr->getArg(0) == child && assignmentOp)
break;
else if (op == OO_GreaterGreaterEqual && operatorCallExpr->getArg(1) == child)
break; // this is a write-only call
else
{
bPotentiallyReadFrom = true;
break;
}
}
else if (auto cxxMemberCallExpr = dyn_cast<CXXMemberCallExpr>(parent))
{
bool bWriteOnlyCall = false;
const CXXMethodDecl* callee = cxxMemberCallExpr->getMethodDecl();
if (callee)
{
const Expr* tmp = dyn_cast<Expr>(child);
if (tmp->isBoundMemberFunction(compiler.getASTContext()))
{
tmp = dyn_cast<MemberExpr>(tmp)->getBase();
}
if (cxxMemberCallExpr->getImplicitObjectArgument() == tmp)
{
// FIXME perhaps a better solution here would be some kind of SAL_PARAM_WRITEONLY attribute
// which we could scatter around.
std::string name = callee->getNameAsString();
std::transform(name.begin(), name.end(), name.begin(), easytolower);
if (startswith(name, "emplace") || name == "insert" || name == "erase"
|| name == "remove" || name == "remove_if" || name == "sort"
|| name == "push_back" || name == "pop_back" || name == "push_front"
|| name == "pop_front" || name == "reserve" || name == "resize"
|| name == "reset" || name == "clear" || name == "fill")
// write-only modifications to collections
bWriteOnlyCall = true;
else if (name == "dispose" || name == "disposeAndClear" || name == "swap")
// we're abusing the write-only analysis here to look for fields which don't have anything useful
// being done to them, so we're ignoring things like std::vector::clear, std::vector::swap,
// and VclPtr::disposeAndClear
bWriteOnlyCall = true;
}
}
if (!bWriteOnlyCall)
bPotentiallyReadFrom = true;
break;
}
else if (auto callExpr = dyn_cast<CallExpr>(parent))
{
bool bWriteOnlyCall = false;
// check for calls to ReadXXX(foo) type methods, where foo is write-only
auto callee = getCallee(callExpr);
if (callee)
{
// FIXME perhaps a better solution here would be some kind of SAL_PARAM_WRITEONLY attribute
// which we could scatter around.
std::string name = callee->getNameAsString();
std::transform(name.begin(), name.end(), name.begin(), easytolower);
if (startswith(name, "read"))
// this is a write-only call
bWriteOnlyCall = true;
}
if (!bWriteOnlyCall)
bPotentiallyReadFrom = true;
break;
}
else if (isa<ReturnStmt>(parent) || isa<CXXConstructExpr>(parent)
|| isa<ConditionalOperator>(parent) || isa<SwitchStmt>(parent)
|| isa<DeclStmt>(parent) || isa<WhileStmt>(parent) || isa<CXXNewExpr>(parent)
|| isa<ForStmt>(parent) || isa<InitListExpr>(parent)
|| isa<CXXDependentScopeMemberExpr>(parent) || isa<UnresolvedMemberExpr>(parent)
|| isa<MaterializeTemporaryExpr>(parent))
{
bPotentiallyReadFrom = true;
break;
}
else if (isa<CXXDeleteExpr>(parent) || isa<UnaryExprOrTypeTraitExpr>(parent)
|| isa<CXXUnresolvedConstructExpr>(parent) || isa<CompoundStmt>(parent)
|| isa<LabelStmt>(parent) || isa<CXXForRangeStmt>(parent)
|| isa<CXXTypeidExpr>(parent) || isa<DefaultStmt>(parent)
|| isa<GCCAsmStmt>(parent) || isa<LambdaExpr>(parent) // TODO
|| isa<CXXDefaultArgExpr>(parent) || isa<AtomicExpr>(parent)
|| isa<VAArgExpr>(parent) || isa<DeclRefExpr>(parent)
#if CLANG_VERSION >= 80000
|| isa<ConstantExpr>(parent)
#endif
|| isa<SubstNonTypeTemplateParmExpr>(parent))
{
break;
}
else
{
bPotentiallyReadFrom = true;
bDump = true;
break;
}
} while (true);
if (bDump)
{
report(DiagnosticsEngine::Warning, "oh dear, what can the matter be?",
compat::getBeginLoc(declRefExpr))
<< declRefExpr->getSourceRange();
report(DiagnosticsEngine::Note, "parent over here", compat::getBeginLoc(parent))
<< parent->getSourceRange();
parent->dump();
declRefExpr->dump();
}
if (bPotentiallyReadFrom)
readFromSet.insert(niceName(varDecl));
}
void UnusedVarsGlobal::checkIfWrittenTo(const VarDecl* varDecl, const DeclRefExpr* declRefExpr)
{
// if we're inside a block that looks like
// if (varDecl)
// ...
// then writes to this field don't matter, because unless we find another write to this field, this field is dead
if (std::find(insideConditionalCheckOfVarSet.begin(), insideConditionalCheckOfVarSet.end(),
varDecl)
!= insideConditionalCheckOfVarSet.end())
return;
auto parentsRange = compiler.getASTContext().getParents(*declRefExpr);
const Stmt* child = declRefExpr;
const Stmt* parent
= parentsRange.begin() == parentsRange.end() ? nullptr : parentsRange.begin()->get<Stmt>();
// walk up the tree until we find something interesting
bool bPotentiallyWrittenTo = false;
bool bDump = false;
auto walkUp = [&]() {
child = parent;
auto parentsRange = compiler.getASTContext().getParents(*parent);
parent = parentsRange.begin() == parentsRange.end() ? nullptr
: parentsRange.begin()->get<Stmt>();
};
do
{
if (!parent)
{
// check if we have an expression like
// int& r = m_field;
auto parentsRange = compiler.getASTContext().getParents(*child);
if (parentsRange.begin() != parentsRange.end())
{
auto varDecl = dyn_cast_or_null<VarDecl>(parentsRange.begin()->get<Decl>());
// The isImplicit() call is to avoid triggering when we see the vardecl which is part of a for-range statement,
// which is of type 'T&&' and also an l-value-ref ?
if (varDecl && !varDecl->isImplicit()
&& loplugin::TypeCheck(varDecl->getType()).LvalueReference().NonConst())
{
bPotentiallyWrittenTo = true;
}
}
break;
}
if (isa<CXXReinterpretCastExpr>(parent))
{
// once we see one of these, there is not much useful we can know
bPotentiallyWrittenTo = true;
break;
}
else if (isa<CastExpr>(parent) || isa<MemberExpr>(parent) || isa<ParenExpr>(parent)
|| isa<ParenListExpr>(parent) || isa<ArrayInitLoopExpr>(parent)
|| isa<ExprWithCleanups>(parent))
{
walkUp();
}
else if (auto unaryOperator = dyn_cast<UnaryOperator>(parent))
{
UnaryOperator::Opcode op = unaryOperator->getOpcode();
if (op == UO_AddrOf || op == UO_PostInc || op == UO_PostDec || op == UO_PreInc
|| op == UO_PreDec)
{
bPotentiallyWrittenTo = true;
}
break;
}
else if (auto arraySubscriptExpr = dyn_cast<ArraySubscriptExpr>(parent))
{
if (arraySubscriptExpr->getIdx() == child)
break;
walkUp();
}
else if (auto operatorCallExpr = dyn_cast<CXXOperatorCallExpr>(parent))
{
auto callee = getCallee(operatorCallExpr);
if (callee)
{
// if calling a non-const operator on the field
auto calleeMethodDecl = callee->getAsCXXMethodDecl();
if (calleeMethodDecl && operatorCallExpr->getArg(0) == child)
{
if (!calleeMethodDecl->isConst())
bPotentiallyWrittenTo
= checkForWriteWhenUsingCollectionType(calleeMethodDecl);
}
else if (IsPassedByNonConst(varDecl, child, operatorCallExpr, *callee))
{
bPotentiallyWrittenTo = true;
}
}
else
bPotentiallyWrittenTo = true; // conservative, could improve
break;
}
else if (auto cxxMemberCallExpr = dyn_cast<CXXMemberCallExpr>(parent))
{
const CXXMethodDecl* calleeMethodDecl = cxxMemberCallExpr->getMethodDecl();
if (calleeMethodDecl)
{
// if calling a non-const method on the field
const Expr* tmp = dyn_cast<Expr>(child);
if (tmp->isBoundMemberFunction(compiler.getASTContext()))
{
tmp = dyn_cast<MemberExpr>(tmp)->getBase();
}
if (cxxMemberCallExpr->getImplicitObjectArgument() == tmp)
{
if (!calleeMethodDecl->isConst())
bPotentiallyWrittenTo
= checkForWriteWhenUsingCollectionType(calleeMethodDecl);
break;
}
else if (IsPassedByNonConst(varDecl, child, cxxMemberCallExpr,
CalleeWrapper(calleeMethodDecl)))
bPotentiallyWrittenTo = true;
}
else
bPotentiallyWrittenTo = true; // can happen in templates
break;
}
else if (auto cxxConstructExpr = dyn_cast<CXXConstructExpr>(parent))
{
if (IsPassedByNonConst(varDecl, child, cxxConstructExpr,
CalleeWrapper(cxxConstructExpr)))
bPotentiallyWrittenTo = true;
break;
}
else if (auto callExpr = dyn_cast<CallExpr>(parent))
{
auto callee = getCallee(callExpr);
if (callee)
{
if (IsPassedByNonConst(varDecl, child, callExpr, *callee))
bPotentiallyWrittenTo = true;
}
else
bPotentiallyWrittenTo = true; // conservative, could improve
break;
}
else if (auto binaryOp = dyn_cast<BinaryOperator>(parent))
{
BinaryOperator::Opcode op = binaryOp->getOpcode();
const bool assignmentOp = op == BO_Assign || 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;
if (assignmentOp)
{
if (binaryOp->getLHS() == child)
bPotentiallyWrittenTo = true;
else if (loplugin::TypeCheck(binaryOp->getLHS()->getType())
.LvalueReference()
.NonConst())
// if the LHS is a non-const reference, we could write to the field later on
bPotentiallyWrittenTo = true;
}
break;
}
else if (isa<ReturnStmt>(parent))
{
if (insideFunctionDecl)
{
auto tc = loplugin::TypeCheck(insideFunctionDecl->getReturnType());
if (tc.LvalueReference().NonConst())
bPotentiallyWrittenTo = true;
}
break;
}
else if (isa<ConditionalOperator>(parent) || isa<SwitchStmt>(parent)
|| isa<DeclStmt>(parent) || isa<WhileStmt>(parent) || isa<CXXNewExpr>(parent)
|| isa<ForStmt>(parent) || isa<InitListExpr>(parent)
|| isa<CXXDependentScopeMemberExpr>(parent) || isa<UnresolvedMemberExpr>(parent)
|| isa<MaterializeTemporaryExpr>(parent) || isa<IfStmt>(parent)
|| isa<DoStmt>(parent) || isa<CXXDeleteExpr>(parent)
|| isa<UnaryExprOrTypeTraitExpr>(parent) || isa<CXXUnresolvedConstructExpr>(parent)
|| isa<CompoundStmt>(parent) || isa<LabelStmt>(parent)
|| isa<CXXForRangeStmt>(parent) || isa<CXXTypeidExpr>(parent)
|| isa<DefaultStmt>(parent) || isa<GCCAsmStmt>(parent)
#if CLANG_VERSION >= 80000
|| isa<ConstantExpr>(parent)
#endif
|| isa<AtomicExpr>(parent) || isa<CXXDefaultArgExpr>(parent)
|| isa<VAArgExpr>(parent) || isa<DeclRefExpr>(parent)
|| isa<SubstNonTypeTemplateParmExpr>(parent) || isa<LambdaExpr>(parent)) // TODO
{
break;
}
else
{
bPotentiallyWrittenTo = true;
bDump = true;
break;
}
} while (true);
if (bDump)
{
report(DiagnosticsEngine::Warning, "oh dear, what can the matter be? writtenTo=%0",
compat::getBeginLoc(declRefExpr))
<< bPotentiallyWrittenTo << declRefExpr->getSourceRange();
if (parent)
{
report(DiagnosticsEngine::Note, "parent over here", compat::getBeginLoc(parent))
<< parent->getSourceRange();
parent->dump();
}
declRefExpr->dump();
varDecl->getType()->dump();
}
if (bPotentiallyWrittenTo)
writeToSet.insert(niceName(varDecl));
}
// return true if this not a collection type, or if it is a collection type, and we might be writing to it
bool UnusedVarsGlobal::checkForWriteWhenUsingCollectionType(const CXXMethodDecl* calleeMethodDecl)
{
auto const tc = loplugin::TypeCheck(calleeMethodDecl->getParent());
bool listLike = false, setLike = false, mapLike = false, cssSequence = false;
if (tc.Class("deque").StdNamespace() || tc.Class("list").StdNamespace()
|| tc.Class("queue").StdNamespace() || tc.Class("vector").StdNamespace())
{
listLike = true;
}
else if (tc.Class("set").StdNamespace() || tc.Class("unordered_set").StdNamespace())
{
setLike = true;
}
else if (tc.Class("map").StdNamespace() || tc.Class("unordered_map").StdNamespace())
{
mapLike = true;
}
else if (tc.Class("Sequence")
.Namespace("uno")
.Namespace("star")
.Namespace("sun")
.Namespace("com")
.GlobalNamespace())
{
cssSequence = true;
}
else
return true;
if (calleeMethodDecl->isOverloadedOperator())
{
auto oo = calleeMethodDecl->getOverloadedOperator();
if (oo == OO_Equal)
return true;
// This is operator[]. We only care about things that add elements to the collection.
// if nothing modifies the size of the collection, then nothing useful
// is stored in it.
if (listLike)
return false;
return true;
}
auto name = calleeMethodDecl->getName();
if (listLike || setLike || mapLike)
{
if (name == "reserve" || name == "shrink_to_fit" || name == "clear" || name == "erase"
|| name == "pop_back" || name == "pop_front" || name == "front" || name == "back"
|| name == "data" || name == "remove" || name == "remove_if" || name == "unique"
|| name == "sort" || name == "begin" || name == "end" || name == "rbegin"
|| name == "rend" || name == "at" || name == "find" || name == "equal_range"
|| name == "lower_bound" || name == "upper_bound")
return false;
}
if (cssSequence)
{
if (name == "getArray" || name == "begin" || name == "end")
return false;
}
return true;
}
bool UnusedVarsGlobal::IsPassedByNonConst(const VarDecl* varDecl, const Stmt* child,
CallerWrapper callExpr, CalleeWrapper calleeFunctionDecl)
{
unsigned len = std::min(callExpr.getNumArgs(), calleeFunctionDecl.getNumParams());
// if it's an array, passing it by value to a method typically means the
// callee takes a pointer and can modify the array
if (varDecl->getType()->isConstantArrayType())
{
for (unsigned i = 0; i < len; ++i)
if (callExpr.getArg(i) == child)
if (loplugin::TypeCheck(calleeFunctionDecl.getParamType(i)).Pointer().NonConst())
return true;
}
else
{
for (unsigned i = 0; i < len; ++i)
if (callExpr.getArg(i) == child)
if (loplugin::TypeCheck(calleeFunctionDecl.getParamType(i))
.LvalueReference()
.NonConst())
return true;
}
return false;
}
llvm::Optional<CalleeWrapper> UnusedVarsGlobal::getCallee(CallExpr const* callExpr)
{
FunctionDecl const* functionDecl = callExpr->getDirectCallee();
if (functionDecl)
return CalleeWrapper(functionDecl);
// Extract the functionprototype from a type
clang::Type const* calleeType = callExpr->getCallee()->getType().getTypePtr();
if (auto pointerType = calleeType->getUnqualifiedDesugaredType()->getAs<clang::PointerType>())
{
if (auto prototype = pointerType->getPointeeType()
->getUnqualifiedDesugaredType()
->getAs<FunctionProtoType>())
{
return CalleeWrapper(prototype);
}
}
return llvm::Optional<CalleeWrapper>();
}
loplugin::Plugin::Registration<UnusedVarsGlobal> X("unusedvarsglobal", false);
}
#endif
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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