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//===---------- ExprMutationAnalyzer.cpp ----------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
#include "clang/AST/Expr.h"
#include "clang/AST/OperationKinds.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "llvm/ADT/STLExtras.h"
namespace clang {
using namespace ast_matchers;
namespace {
AST_MATCHER_P(LambdaExpr, hasCaptureInit, const Expr *, E) {
return llvm::is_contained(Node.capture_inits(), E);
}
AST_MATCHER_P(CXXForRangeStmt, hasRangeStmt,
ast_matchers::internal::Matcher<DeclStmt>, InnerMatcher) {
const DeclStmt *const Range = Node.getRangeStmt();
return InnerMatcher.matches(*Range, Finder, Builder);
}
AST_MATCHER_P(Expr, maybeEvalCommaExpr, ast_matchers::internal::Matcher<Expr>,
InnerMatcher) {
const Expr *Result = &Node;
while (const auto *BOComma =
dyn_cast_or_null<BinaryOperator>(Result->IgnoreParens())) {
if (!BOComma->isCommaOp())
break;
Result = BOComma->getRHS();
}
return InnerMatcher.matches(*Result, Finder, Builder);
}
AST_MATCHER_P(Stmt, canResolveToExpr, ast_matchers::internal::Matcher<Stmt>,
InnerMatcher) {
auto *Exp = dyn_cast<Expr>(&Node);
if (!Exp) {
return stmt().matches(Node, Finder, Builder);
}
auto DerivedToBase = [](const ast_matchers::internal::Matcher<Expr> &Inner) {
return implicitCastExpr(anyOf(hasCastKind(CK_DerivedToBase),
hasCastKind(CK_UncheckedDerivedToBase)),
hasSourceExpression(Inner));
};
auto IgnoreDerivedToBase =
[&DerivedToBase](const ast_matchers::internal::Matcher<Expr> &Inner) {
return ignoringParens(expr(anyOf(Inner, DerivedToBase(Inner))));
};
// The 'ConditionalOperator' matches on `<anything> ? <expr> : <expr>`.
// This matching must be recursive because `<expr>` can be anything resolving
// to the `InnerMatcher`, for example another conditional operator.
// The edge-case `BaseClass &b = <cond> ? DerivedVar1 : DerivedVar2;`
// is handled, too. The implicit cast happens outside of the conditional.
// This is matched by `IgnoreDerivedToBase(canResolveToExpr(InnerMatcher))`
// below.
auto const ConditionalOperator = conditionalOperator(anyOf(
hasTrueExpression(ignoringParens(canResolveToExpr(InnerMatcher))),
hasFalseExpression(ignoringParens(canResolveToExpr(InnerMatcher)))));
auto const ElvisOperator = binaryConditionalOperator(anyOf(
hasTrueExpression(ignoringParens(canResolveToExpr(InnerMatcher))),
hasFalseExpression(ignoringParens(canResolveToExpr(InnerMatcher)))));
auto const ComplexMatcher = ignoringParens(
expr(anyOf(IgnoreDerivedToBase(InnerMatcher),
maybeEvalCommaExpr(IgnoreDerivedToBase(InnerMatcher)),
IgnoreDerivedToBase(ConditionalOperator),
IgnoreDerivedToBase(ElvisOperator))));
return ComplexMatcher.matches(*Exp, Finder, Builder);
}
// Similar to 'hasAnyArgument', but does not work because 'InitListExpr' does
// not have the 'arguments()' method.
AST_MATCHER_P(InitListExpr, hasAnyInit, ast_matchers::internal::Matcher<Expr>,
InnerMatcher) {
for (const Expr *Arg : Node.inits()) {
ast_matchers::internal::BoundNodesTreeBuilder Result(*Builder);
if (InnerMatcher.matches(*Arg, Finder, &Result)) {
*Builder = std::move(Result);
return true;
}
}
return false;
}
const ast_matchers::internal::VariadicDynCastAllOfMatcher<Stmt, CXXTypeidExpr>
cxxTypeidExpr;
AST_MATCHER(CXXTypeidExpr, isPotentiallyEvaluated) {
return Node.isPotentiallyEvaluated();
}
AST_MATCHER_P(GenericSelectionExpr, hasControllingExpr,
ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
return InnerMatcher.matches(*Node.getControllingExpr(), Finder, Builder);
}
const auto nonConstReferenceType = [] {
return hasUnqualifiedDesugaredType(
referenceType(pointee(unless(isConstQualified()))));
};
const auto nonConstPointerType = [] {
return hasUnqualifiedDesugaredType(
pointerType(pointee(unless(isConstQualified()))));
};
const auto isMoveOnly = [] {
return cxxRecordDecl(
hasMethod(cxxConstructorDecl(isMoveConstructor(), unless(isDeleted()))),
hasMethod(cxxMethodDecl(isMoveAssignmentOperator(), unless(isDeleted()))),
unless(anyOf(hasMethod(cxxConstructorDecl(isCopyConstructor(),
unless(isDeleted()))),
hasMethod(cxxMethodDecl(isCopyAssignmentOperator(),
unless(isDeleted()))))));
};
template <class T> struct NodeID;
template <> struct NodeID<Expr> { static constexpr StringRef value = "expr"; };
template <> struct NodeID<Decl> { static constexpr StringRef value = "decl"; };
constexpr StringRef NodeID<Expr>::value;
constexpr StringRef NodeID<Decl>::value;
template <class T, class F = const Stmt *(ExprMutationAnalyzer::*)(const T *)>
const Stmt *tryEachMatch(ArrayRef<ast_matchers::BoundNodes> Matches,
ExprMutationAnalyzer *Analyzer, F Finder) {
const StringRef ID = NodeID<T>::value;
for (const auto &Nodes : Matches) {
if (const Stmt *S = (Analyzer->*Finder)(Nodes.getNodeAs<T>(ID)))
return S;
}
return nullptr;
}
} // namespace
const Stmt *ExprMutationAnalyzer::findMutation(const Expr *Exp) {
return findMutationMemoized(Exp,
{&ExprMutationAnalyzer::findDirectMutation,
&ExprMutationAnalyzer::findMemberMutation,
&ExprMutationAnalyzer::findArrayElementMutation,
&ExprMutationAnalyzer::findCastMutation,
&ExprMutationAnalyzer::findRangeLoopMutation,
&ExprMutationAnalyzer::findReferenceMutation,
&ExprMutationAnalyzer::findFunctionArgMutation},
Results);
}
const Stmt *ExprMutationAnalyzer::findMutation(const Decl *Dec) {
return tryEachDeclRef(Dec, &ExprMutationAnalyzer::findMutation);
}
const Stmt *ExprMutationAnalyzer::findPointeeMutation(const Expr *Exp) {
return findMutationMemoized(Exp, {/*TODO*/}, PointeeResults);
}
const Stmt *ExprMutationAnalyzer::findPointeeMutation(const Decl *Dec) {
return tryEachDeclRef(Dec, &ExprMutationAnalyzer::findPointeeMutation);
}
const Stmt *ExprMutationAnalyzer::findMutationMemoized(
const Expr *Exp, llvm::ArrayRef<MutationFinder> Finders,
ResultMap &MemoizedResults) {
const auto Memoized = MemoizedResults.find(Exp);
if (Memoized != MemoizedResults.end())
return Memoized->second;
if (isUnevaluated(Exp))
return MemoizedResults[Exp] = nullptr;
for (const auto &Finder : Finders) {
if (const Stmt *S = (this->*Finder)(Exp))
return MemoizedResults[Exp] = S;
}
return MemoizedResults[Exp] = nullptr;
}
const Stmt *ExprMutationAnalyzer::tryEachDeclRef(const Decl *Dec,
MutationFinder Finder) {
const auto Refs =
match(findAll(declRefExpr(to(equalsNode(Dec))).bind(NodeID<Expr>::value)),
Stm, Context);
for (const auto &RefNodes : Refs) {
const auto *E = RefNodes.getNodeAs<Expr>(NodeID<Expr>::value);
if ((this->*Finder)(E))
return E;
}
return nullptr;
}
bool ExprMutationAnalyzer::isUnevaluated(const Stmt *Exp, const Stmt &Stm,
ASTContext &Context) {
return selectFirst<Stmt>(
NodeID<Expr>::value,
match(
findAll(
stmt(canResolveToExpr(equalsNode(Exp)),
anyOf(
// `Exp` is part of the underlying expression of
// decltype/typeof if it has an ancestor of
// typeLoc.
hasAncestor(typeLoc(unless(
hasAncestor(unaryExprOrTypeTraitExpr())))),
hasAncestor(expr(anyOf(
// `UnaryExprOrTypeTraitExpr` is unevaluated
// unless it's sizeof on VLA.
unaryExprOrTypeTraitExpr(unless(sizeOfExpr(
hasArgumentOfType(variableArrayType())))),
// `CXXTypeidExpr` is unevaluated unless it's
// applied to an expression of glvalue of
// polymorphic class type.
cxxTypeidExpr(
unless(isPotentiallyEvaluated())),
// The controlling expression of
// `GenericSelectionExpr` is unevaluated.
genericSelectionExpr(hasControllingExpr(
hasDescendant(equalsNode(Exp)))),
cxxNoexceptExpr())))))
.bind(NodeID<Expr>::value)),
Stm, Context)) != nullptr;
}
bool ExprMutationAnalyzer::isUnevaluated(const Expr *Exp) {
return isUnevaluated(Exp, Stm, Context);
}
const Stmt *
ExprMutationAnalyzer::findExprMutation(ArrayRef<BoundNodes> Matches) {
return tryEachMatch<Expr>(Matches, this, &ExprMutationAnalyzer::findMutation);
}
const Stmt *
ExprMutationAnalyzer::findDeclMutation(ArrayRef<BoundNodes> Matches) {
return tryEachMatch<Decl>(Matches, this, &ExprMutationAnalyzer::findMutation);
}
const Stmt *ExprMutationAnalyzer::findExprPointeeMutation(
ArrayRef<ast_matchers::BoundNodes> Matches) {
return tryEachMatch<Expr>(Matches, this,
&ExprMutationAnalyzer::findPointeeMutation);
}
const Stmt *ExprMutationAnalyzer::findDeclPointeeMutation(
ArrayRef<ast_matchers::BoundNodes> Matches) {
return tryEachMatch<Decl>(Matches, this,
&ExprMutationAnalyzer::findPointeeMutation);
}
const Stmt *ExprMutationAnalyzer::findDirectMutation(const Expr *Exp) {
// LHS of any assignment operators.
const auto AsAssignmentLhs = binaryOperator(
isAssignmentOperator(), hasLHS(canResolveToExpr(equalsNode(Exp))));
// Operand of increment/decrement operators.
const auto AsIncDecOperand =
unaryOperator(anyOf(hasOperatorName("++"), hasOperatorName("--")),
hasUnaryOperand(canResolveToExpr(equalsNode(Exp))));
// Invoking non-const member function.
// A member function is assumed to be non-const when it is unresolved.
const auto NonConstMethod = cxxMethodDecl(unless(isConst()));
const auto AsNonConstThis = expr(anyOf(
cxxMemberCallExpr(callee(NonConstMethod),
on(canResolveToExpr(equalsNode(Exp)))),
cxxOperatorCallExpr(callee(NonConstMethod),
hasArgument(0, canResolveToExpr(equalsNode(Exp)))),
// In case of a templated type, calling overloaded operators is not
// resolved and modelled as `binaryOperator` on a dependent type.
// Such instances are considered a modification, because they can modify
// in different instantiations of the template.
binaryOperator(hasEitherOperand(
allOf(ignoringImpCasts(canResolveToExpr(equalsNode(Exp))),
isTypeDependent()))),
// Within class templates and member functions the member expression might
// not be resolved. In that case, the `callExpr` is considered to be a
// modification.
callExpr(
callee(expr(anyOf(unresolvedMemberExpr(hasObjectExpression(
canResolveToExpr(equalsNode(Exp)))),
cxxDependentScopeMemberExpr(hasObjectExpression(
canResolveToExpr(equalsNode(Exp)))))))),
// Match on a call to a known method, but the call itself is type
// dependent (e.g. `vector<T> v; v.push(T{});` in a templated function).
callExpr(allOf(isTypeDependent(),
callee(memberExpr(hasDeclaration(NonConstMethod),
hasObjectExpression(canResolveToExpr(
equalsNode(Exp)))))))));
// Taking address of 'Exp'.
// We're assuming 'Exp' is mutated as soon as its address is taken, though in
// theory we can follow the pointer and see whether it escaped `Stm` or is
// dereferenced and then mutated. This is left for future improvements.
const auto AsAmpersandOperand =
unaryOperator(hasOperatorName("&"),
// A NoOp implicit cast is adding const.
unless(hasParent(implicitCastExpr(hasCastKind(CK_NoOp)))),
hasUnaryOperand(canResolveToExpr(equalsNode(Exp))));
const auto AsPointerFromArrayDecay =
castExpr(hasCastKind(CK_ArrayToPointerDecay),
unless(hasParent(arraySubscriptExpr())),
has(canResolveToExpr(equalsNode(Exp))));
// Treat calling `operator->()` of move-only classes as taking address.
// These are typically smart pointers with unique ownership so we treat
// mutation of pointee as mutation of the smart pointer itself.
const auto AsOperatorArrowThis = cxxOperatorCallExpr(
hasOverloadedOperatorName("->"),
callee(
cxxMethodDecl(ofClass(isMoveOnly()), returns(nonConstPointerType()))),
argumentCountIs(1), hasArgument(0, canResolveToExpr(equalsNode(Exp))));
// Used as non-const-ref argument when calling a function.
// An argument is assumed to be non-const-ref when the function is unresolved.
// Instantiated template functions are not handled here but in
// findFunctionArgMutation which has additional smarts for handling forwarding
// references.
const auto NonConstRefParam = forEachArgumentWithParamType(
anyOf(canResolveToExpr(equalsNode(Exp)),
memberExpr(hasObjectExpression(canResolveToExpr(equalsNode(Exp))))),
nonConstReferenceType());
const auto NotInstantiated = unless(hasDeclaration(isInstantiated()));
const auto TypeDependentCallee =
callee(expr(anyOf(unresolvedLookupExpr(), unresolvedMemberExpr(),
cxxDependentScopeMemberExpr(),
hasType(templateTypeParmType()), isTypeDependent())));
const auto AsNonConstRefArg = anyOf(
callExpr(NonConstRefParam, NotInstantiated),
cxxConstructExpr(NonConstRefParam, NotInstantiated),
callExpr(TypeDependentCallee,
hasAnyArgument(canResolveToExpr(equalsNode(Exp)))),
cxxUnresolvedConstructExpr(
hasAnyArgument(canResolveToExpr(equalsNode(Exp)))),
// Previous False Positive in the following Code:
// `template <typename T> void f() { int i = 42; new Type<T>(i); }`
// Where the constructor of `Type` takes its argument as reference.
// The AST does not resolve in a `cxxConstructExpr` because it is
// type-dependent.
parenListExpr(hasDescendant(expr(canResolveToExpr(equalsNode(Exp))))),
// If the initializer is for a reference type, there is no cast for
// the variable. Values are cast to RValue first.
initListExpr(hasAnyInit(expr(canResolveToExpr(equalsNode(Exp))))));
// Captured by a lambda by reference.
// If we're initializing a capture with 'Exp' directly then we're initializing
// a reference capture.
// For value captures there will be an ImplicitCastExpr <LValueToRValue>.
const auto AsLambdaRefCaptureInit = lambdaExpr(hasCaptureInit(Exp));
// Returned as non-const-ref.
// If we're returning 'Exp' directly then it's returned as non-const-ref.
// For returning by value there will be an ImplicitCastExpr <LValueToRValue>.
// For returning by const-ref there will be an ImplicitCastExpr <NoOp> (for
// adding const.)
const auto AsNonConstRefReturn =
returnStmt(hasReturnValue(canResolveToExpr(equalsNode(Exp))));
// It is used as a non-const-reference for initalizing a range-for loop.
const auto AsNonConstRefRangeInit = cxxForRangeStmt(
hasRangeInit(declRefExpr(allOf(canResolveToExpr(equalsNode(Exp)),
hasType(nonConstReferenceType())))));
const auto Matches = match(
traverse(TK_AsIs,
findAll(stmt(anyOf(AsAssignmentLhs, AsIncDecOperand,
AsNonConstThis, AsAmpersandOperand,
AsPointerFromArrayDecay, AsOperatorArrowThis,
AsNonConstRefArg, AsLambdaRefCaptureInit,
AsNonConstRefReturn, AsNonConstRefRangeInit))
.bind("stmt"))),
Stm, Context);
return selectFirst<Stmt>("stmt", Matches);
}
const Stmt *ExprMutationAnalyzer::findMemberMutation(const Expr *Exp) {
// Check whether any member of 'Exp' is mutated.
const auto MemberExprs =
match(findAll(expr(anyOf(memberExpr(hasObjectExpression(
canResolveToExpr(equalsNode(Exp)))),
cxxDependentScopeMemberExpr(hasObjectExpression(
canResolveToExpr(equalsNode(Exp))))))
.bind(NodeID<Expr>::value)),
Stm, Context);
return findExprMutation(MemberExprs);
}
const Stmt *ExprMutationAnalyzer::findArrayElementMutation(const Expr *Exp) {
// Check whether any element of an array is mutated.
const auto SubscriptExprs =
match(findAll(arraySubscriptExpr(
anyOf(hasBase(canResolveToExpr(equalsNode(Exp))),
hasBase(implicitCastExpr(
allOf(hasCastKind(CK_ArrayToPointerDecay),
hasSourceExpression(canResolveToExpr(
equalsNode(Exp))))))))
.bind(NodeID<Expr>::value)),
Stm, Context);
return findExprMutation(SubscriptExprs);
}
const Stmt *ExprMutationAnalyzer::findCastMutation(const Expr *Exp) {
// If the 'Exp' is explicitly casted to a non-const reference type the
// 'Exp' is considered to be modified.
const auto ExplicitCast = match(
findAll(
stmt(castExpr(hasSourceExpression(canResolveToExpr(equalsNode(Exp))),
explicitCastExpr(
hasDestinationType(nonConstReferenceType()))))
.bind("stmt")),
Stm, Context);
if (const auto *CastStmt = selectFirst<Stmt>("stmt", ExplicitCast))
return CastStmt;
// If 'Exp' is casted to any non-const reference type, check the castExpr.
const auto Casts = match(
findAll(
expr(castExpr(hasSourceExpression(canResolveToExpr(equalsNode(Exp))),
anyOf(explicitCastExpr(
hasDestinationType(nonConstReferenceType())),
implicitCastExpr(hasImplicitDestinationType(
nonConstReferenceType())))))
.bind(NodeID<Expr>::value)),
Stm, Context);
if (const Stmt *S = findExprMutation(Casts))
return S;
// Treat std::{move,forward} as cast.
const auto Calls =
match(findAll(callExpr(callee(namedDecl(
hasAnyName("::std::move", "::std::forward"))),
hasArgument(0, canResolveToExpr(equalsNode(Exp))))
.bind("expr")),
Stm, Context);
return findExprMutation(Calls);
}
const Stmt *ExprMutationAnalyzer::findRangeLoopMutation(const Expr *Exp) {
// Keep the ordering for the specific initialization matches to happen first,
// because it is cheaper to match all potential modifications of the loop
// variable.
// The range variable is a reference to a builtin array. In that case the
// array is considered modified if the loop-variable is a non-const reference.
const auto DeclStmtToNonRefToArray = declStmt(hasSingleDecl(varDecl(hasType(
hasUnqualifiedDesugaredType(referenceType(pointee(arrayType())))))));
const auto RefToArrayRefToElements = match(
findAll(stmt(cxxForRangeStmt(
hasLoopVariable(varDecl(hasType(nonConstReferenceType()))
.bind(NodeID<Decl>::value)),
hasRangeStmt(DeclStmtToNonRefToArray),
hasRangeInit(canResolveToExpr(equalsNode(Exp)))))
.bind("stmt")),
Stm, Context);
if (const auto *BadRangeInitFromArray =
selectFirst<Stmt>("stmt", RefToArrayRefToElements))
return BadRangeInitFromArray;
// Small helper to match special cases in range-for loops.
//
// It is possible that containers do not provide a const-overload for their
// iterator accessors. If this is the case, the variable is used non-const
// no matter what happens in the loop. This requires special detection as it
// is then faster to find all mutations of the loop variable.
// It aims at a different modification as well.
const auto HasAnyNonConstIterator =
anyOf(allOf(hasMethod(allOf(hasName("begin"), unless(isConst()))),
unless(hasMethod(allOf(hasName("begin"), isConst())))),
allOf(hasMethod(allOf(hasName("end"), unless(isConst()))),
unless(hasMethod(allOf(hasName("end"), isConst())))));
const auto DeclStmtToNonConstIteratorContainer = declStmt(
hasSingleDecl(varDecl(hasType(hasUnqualifiedDesugaredType(referenceType(
pointee(hasDeclaration(cxxRecordDecl(HasAnyNonConstIterator)))))))));
const auto RefToContainerBadIterators =
match(findAll(stmt(cxxForRangeStmt(allOf(
hasRangeStmt(DeclStmtToNonConstIteratorContainer),
hasRangeInit(canResolveToExpr(equalsNode(Exp))))))
.bind("stmt")),
Stm, Context);
if (const auto *BadIteratorsContainer =
selectFirst<Stmt>("stmt", RefToContainerBadIterators))
return BadIteratorsContainer;
// If range for looping over 'Exp' with a non-const reference loop variable,
// check all declRefExpr of the loop variable.
const auto LoopVars =
match(findAll(cxxForRangeStmt(
hasLoopVariable(varDecl(hasType(nonConstReferenceType()))
.bind(NodeID<Decl>::value)),
hasRangeInit(canResolveToExpr(equalsNode(Exp))))),
Stm, Context);
return findDeclMutation(LoopVars);
}
const Stmt *ExprMutationAnalyzer::findReferenceMutation(const Expr *Exp) {
// Follow non-const reference returned by `operator*()` of move-only classes.
// These are typically smart pointers with unique ownership so we treat
// mutation of pointee as mutation of the smart pointer itself.
const auto Ref =
match(findAll(cxxOperatorCallExpr(
hasOverloadedOperatorName("*"),
callee(cxxMethodDecl(ofClass(isMoveOnly()),
returns(nonConstReferenceType()))),
argumentCountIs(1),
hasArgument(0, canResolveToExpr(equalsNode(Exp))))
.bind(NodeID<Expr>::value)),
Stm, Context);
if (const Stmt *S = findExprMutation(Ref))
return S;
// If 'Exp' is bound to a non-const reference, check all declRefExpr to that.
const auto Refs = match(
stmt(forEachDescendant(
varDecl(
hasType(nonConstReferenceType()),
hasInitializer(anyOf(canResolveToExpr(equalsNode(Exp)),
memberExpr(hasObjectExpression(
canResolveToExpr(equalsNode(Exp)))))),
hasParent(declStmt().bind("stmt")),
// Don't follow the reference in range statement, we've
// handled that separately.
unless(hasParent(declStmt(hasParent(
cxxForRangeStmt(hasRangeStmt(equalsBoundNode("stmt"))))))))
.bind(NodeID<Decl>::value))),
Stm, Context);
return findDeclMutation(Refs);
}
const Stmt *ExprMutationAnalyzer::findFunctionArgMutation(const Expr *Exp) {
const auto NonConstRefParam = forEachArgumentWithParam(
canResolveToExpr(equalsNode(Exp)),
parmVarDecl(hasType(nonConstReferenceType())).bind("parm"));
const auto IsInstantiated = hasDeclaration(isInstantiated());
const auto FuncDecl = hasDeclaration(functionDecl().bind("func"));
const auto Matches = match(
traverse(
TK_AsIs,
findAll(
expr(anyOf(callExpr(NonConstRefParam, IsInstantiated, FuncDecl,
unless(callee(namedDecl(hasAnyName(
"::std::move", "::std::forward"))))),
cxxConstructExpr(NonConstRefParam, IsInstantiated,
FuncDecl)))
.bind(NodeID<Expr>::value))),
Stm, Context);
for (const auto &Nodes : Matches) {
const auto *Exp = Nodes.getNodeAs<Expr>(NodeID<Expr>::value);
const auto *Func = Nodes.getNodeAs<FunctionDecl>("func");
if (!Func->getBody() || !Func->getPrimaryTemplate())
return Exp;
const auto *Parm = Nodes.getNodeAs<ParmVarDecl>("parm");
const ArrayRef<ParmVarDecl *> AllParams =
Func->getPrimaryTemplate()->getTemplatedDecl()->parameters();
QualType ParmType =
AllParams[std::min<size_t>(Parm->getFunctionScopeIndex(),
AllParams.size() - 1)]
->getType();
if (const auto *T = ParmType->getAs<PackExpansionType>())
ParmType = T->getPattern();
// If param type is forwarding reference, follow into the function
// definition and see whether the param is mutated inside.
if (const auto *RefType = ParmType->getAs<RValueReferenceType>()) {
if (!RefType->getPointeeType().getQualifiers() &&
RefType->getPointeeType()->getAs<TemplateTypeParmType>()) {
std::unique_ptr<FunctionParmMutationAnalyzer> &Analyzer =
FuncParmAnalyzer[Func];
if (!Analyzer)
Analyzer.reset(new FunctionParmMutationAnalyzer(*Func, Context));
if (Analyzer->findMutation(Parm))
return Exp;
continue;
}
}
// Not forwarding reference.
return Exp;
}
return nullptr;
}
FunctionParmMutationAnalyzer::FunctionParmMutationAnalyzer(
const FunctionDecl &Func, ASTContext &Context)
: BodyAnalyzer(*Func.getBody(), Context) {
if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(&Func)) {
// CXXCtorInitializer might also mutate Param but they're not part of
// function body, check them eagerly here since they're typically trivial.
for (const CXXCtorInitializer *Init : Ctor->inits()) {
ExprMutationAnalyzer InitAnalyzer(*Init->getInit(), Context);
for (const ParmVarDecl *Parm : Ctor->parameters()) {
if (Results.find(Parm) != Results.end())
continue;
if (const Stmt *S = InitAnalyzer.findMutation(Parm))
Results[Parm] = S;
}
}
}
}
const Stmt *
FunctionParmMutationAnalyzer::findMutation(const ParmVarDecl *Parm) {
const auto Memoized = Results.find(Parm);
if (Memoized != Results.end())
return Memoized->second;
if (const Stmt *S = BodyAnalyzer.findMutation(Parm))
return Results[Parm] = S;
return Results[Parm] = nullptr;
}
} // namespace clang