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//===--- UnhandledSelfAssignmentCheck.cpp - clang-tidy --------------------===//
//
// 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 "UnhandledSelfAssignmentCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
using namespace clang::ast_matchers;
namespace clang::tidy::bugprone {
UnhandledSelfAssignmentCheck::UnhandledSelfAssignmentCheck(
StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
WarnOnlyIfThisHasSuspiciousField(
Options.get("WarnOnlyIfThisHasSuspiciousField", true)) {}
void UnhandledSelfAssignmentCheck::storeOptions(
ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "WarnOnlyIfThisHasSuspiciousField",
WarnOnlyIfThisHasSuspiciousField);
}
void UnhandledSelfAssignmentCheck::registerMatchers(MatchFinder *Finder) {
// We don't care about deleted, default or implicit operator implementations.
const auto IsUserDefined = cxxMethodDecl(
isDefinition(), unless(anyOf(isDeleted(), isImplicit(), isDefaulted())));
// We don't need to worry when a copy assignment operator gets the other
// object by value.
const auto HasReferenceParam =
cxxMethodDecl(hasParameter(0, parmVarDecl(hasType(referenceType()))));
// Self-check: Code compares something with 'this' pointer. We don't check
// whether it is actually the parameter what we compare.
const auto HasNoSelfCheck = cxxMethodDecl(unless(hasDescendant(
binaryOperation(hasAnyOperatorName("==", "!="),
hasEitherOperand(ignoringParenCasts(cxxThisExpr()))))));
// Both copy-and-swap and copy-and-move method creates a copy first and
// assign it to 'this' with swap or move.
// In the non-template case, we can search for the copy constructor call.
const auto HasNonTemplateSelfCopy = cxxMethodDecl(
ofClass(cxxRecordDecl(unless(hasAncestor(classTemplateDecl())))),
traverse(TK_AsIs,
hasDescendant(cxxConstructExpr(hasDeclaration(cxxConstructorDecl(
isCopyConstructor(), ofClass(equalsBoundNode("class"))))))));
// In the template case, we need to handle two separate cases: 1) a local
// variable is created with the copy, 2) copy is created only as a temporary
// object.
const auto HasTemplateSelfCopy = cxxMethodDecl(
ofClass(cxxRecordDecl(hasAncestor(classTemplateDecl()))),
anyOf(hasDescendant(
varDecl(hasType(cxxRecordDecl(equalsBoundNode("class"))),
hasDescendant(parenListExpr()))),
hasDescendant(cxxUnresolvedConstructExpr(hasDescendant(declRefExpr(
hasType(cxxRecordDecl(equalsBoundNode("class")))))))));
// If inside the copy assignment operator another assignment operator is
// called on 'this' we assume that self-check might be handled inside
// this nested operator.
const auto HasNoNestedSelfAssign =
cxxMethodDecl(unless(hasDescendant(cxxMemberCallExpr(callee(cxxMethodDecl(
hasName("operator="), ofClass(equalsBoundNode("class"))))))));
// Checking that some kind of constructor is called and followed by a `swap`:
// T& operator=(const T& other) {
// T tmp{this->internal_data(), some, other, args};
// swap(tmp);
// return *this;
// }
const auto HasCopyAndSwap = cxxMethodDecl(
ofClass(cxxRecordDecl()),
hasBody(compoundStmt(
hasDescendant(
varDecl(hasType(cxxRecordDecl(equalsBoundNode("class"))))
.bind("tmp_var")),
hasDescendant(stmt(anyOf(
cxxMemberCallExpr(hasArgument(
0, declRefExpr(to(varDecl(equalsBoundNode("tmp_var")))))),
callExpr(
callee(functionDecl(hasName("swap"))), argumentCountIs(2),
hasAnyArgument(
declRefExpr(to(varDecl(equalsBoundNode("tmp_var"))))),
hasAnyArgument(unaryOperator(has(cxxThisExpr()),
hasOperatorName("*"))))))))));
DeclarationMatcher AdditionalMatcher = cxxMethodDecl();
if (WarnOnlyIfThisHasSuspiciousField) {
// Matcher for standard smart pointers.
const auto SmartPointerType = qualType(hasUnqualifiedDesugaredType(
recordType(hasDeclaration(classTemplateSpecializationDecl(
anyOf(allOf(hasAnyName("::std::shared_ptr", "::std::weak_ptr",
"::std::auto_ptr"),
templateArgumentCountIs(1)),
allOf(hasName("::std::unique_ptr"),
templateArgumentCountIs(2))))))));
// We will warn only if the class has a pointer or a C array field which
// probably causes a problem during self-assignment (e.g. first resetting
// the pointer member, then trying to access the object pointed by the
// pointer, or memcpy overlapping arrays).
AdditionalMatcher = cxxMethodDecl(ofClass(cxxRecordDecl(
has(fieldDecl(anyOf(hasType(pointerType()), hasType(SmartPointerType),
hasType(arrayType())))))));
}
Finder->addMatcher(
cxxMethodDecl(
ofClass(cxxRecordDecl().bind("class")), isCopyAssignmentOperator(),
IsUserDefined, HasReferenceParam, HasNoSelfCheck,
unless(HasNonTemplateSelfCopy), unless(HasTemplateSelfCopy),
unless(HasCopyAndSwap), HasNoNestedSelfAssign, AdditionalMatcher)
.bind("copyAssignmentOperator"),
this);
}
void UnhandledSelfAssignmentCheck::check(
const MatchFinder::MatchResult &Result) {
const auto *MatchedDecl =
Result.Nodes.getNodeAs<CXXMethodDecl>("copyAssignmentOperator");
diag(MatchedDecl->getLocation(),
"operator=() does not handle self-assignment properly");
}
} // namespace clang::tidy::bugprone
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