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//===--- PassByValueCheck.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 "PassByValueCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Lex/Lexer.h"
#include "clang/Lex/Preprocessor.h"
using namespace clang::ast_matchers;
using namespace llvm;
namespace clang {
namespace tidy {
namespace modernize {
namespace {
/// \brief Matches move-constructible classes.
///
/// Given
/// \code
/// // POD types are trivially move constructible.
/// struct Foo { int a; };
///
/// struct Bar {
/// Bar(Bar &&) = deleted;
/// int a;
/// };
/// \endcode
/// recordDecl(isMoveConstructible())
/// matches "Foo".
AST_MATCHER(CXXRecordDecl, isMoveConstructible) {
for (const CXXConstructorDecl *Ctor : Node.ctors()) {
if (Ctor->isMoveConstructor() && !Ctor->isDeleted())
return true;
}
return false;
}
} // namespace
static TypeMatcher constRefType() {
return lValueReferenceType(pointee(isConstQualified()));
}
static TypeMatcher nonConstValueType() {
return qualType(unless(anyOf(referenceType(), isConstQualified())));
}
/// \brief Whether or not \p ParamDecl is used exactly one time in \p Ctor.
///
/// Checks both in the init-list and the body of the constructor.
static bool paramReferredExactlyOnce(const CXXConstructorDecl *Ctor,
const ParmVarDecl *ParamDecl) {
/// \brief \c clang::RecursiveASTVisitor that checks that the given
/// \c ParmVarDecl is used exactly one time.
///
/// \see ExactlyOneUsageVisitor::hasExactlyOneUsageIn()
class ExactlyOneUsageVisitor
: public RecursiveASTVisitor<ExactlyOneUsageVisitor> {
friend class RecursiveASTVisitor<ExactlyOneUsageVisitor>;
public:
ExactlyOneUsageVisitor(const ParmVarDecl *ParamDecl)
: ParamDecl(ParamDecl) {}
/// \brief Whether or not the parameter variable is referred only once in
/// the
/// given constructor.
bool hasExactlyOneUsageIn(const CXXConstructorDecl *Ctor) {
Count = 0;
TraverseDecl(const_cast<CXXConstructorDecl *>(Ctor));
return Count == 1;
}
private:
/// \brief Counts the number of references to a variable.
///
/// Stops the AST traversal if more than one usage is found.
bool VisitDeclRefExpr(DeclRefExpr *D) {
if (const ParmVarDecl *To = dyn_cast<ParmVarDecl>(D->getDecl())) {
if (To == ParamDecl) {
++Count;
if (Count > 1) {
// No need to look further, used more than once.
return false;
}
}
}
return true;
}
const ParmVarDecl *ParamDecl;
unsigned Count;
};
return ExactlyOneUsageVisitor(ParamDecl).hasExactlyOneUsageIn(Ctor);
}
/// \brief Find all references to \p ParamDecl across all of the
/// redeclarations of \p Ctor.
static SmallVector<const ParmVarDecl *, 2>
collectParamDecls(const CXXConstructorDecl *Ctor,
const ParmVarDecl *ParamDecl) {
SmallVector<const ParmVarDecl *, 2> Results;
unsigned ParamIdx = ParamDecl->getFunctionScopeIndex();
for (const FunctionDecl *Redecl : Ctor->redecls())
Results.push_back(Redecl->getParamDecl(ParamIdx));
return Results;
}
PassByValueCheck::PassByValueCheck(StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
IncludeStyle(utils::IncludeSorter::parseIncludeStyle(
Options.getLocalOrGlobal("IncludeStyle", "llvm"))),
ValuesOnly(Options.get("ValuesOnly", 0) != 0) {}
void PassByValueCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "IncludeStyle",
utils::IncludeSorter::toString(IncludeStyle));
Options.store(Opts, "ValuesOnly", ValuesOnly);
}
void PassByValueCheck::registerMatchers(MatchFinder *Finder) {
// Only register the matchers for C++; the functionality currently does not
// provide any benefit to other languages, despite being benign.
if (!getLangOpts().CPlusPlus)
return;
Finder->addMatcher(
cxxConstructorDecl(
forEachConstructorInitializer(
cxxCtorInitializer(
unless(isBaseInitializer()),
// Clang builds a CXXConstructExpr only when it knows which
// constructor will be called. In dependent contexts a
// ParenListExpr is generated instead of a CXXConstructExpr,
// filtering out templates automatically for us.
withInitializer(cxxConstructExpr(
has(ignoringParenImpCasts(declRefExpr(to(
parmVarDecl(
hasType(qualType(
// Match only const-ref or a non-const value
// parameters. Rvalues and const-values
// shouldn't be modified.
ValuesOnly ? nonConstValueType()
: anyOf(constRefType(),
nonConstValueType()))))
.bind("Param"))))),
hasDeclaration(cxxConstructorDecl(
isCopyConstructor(), unless(isDeleted()),
hasDeclContext(
cxxRecordDecl(isMoveConstructible())))))))
.bind("Initializer")))
.bind("Ctor"),
this);
}
void PassByValueCheck::registerPPCallbacks(const SourceManager &SM,
Preprocessor *PP,
Preprocessor *ModuleExpanderPP) {
// Only register the preprocessor callbacks for C++; the functionality
// currently does not provide any benefit to other languages, despite being
// benign.
if (getLangOpts().CPlusPlus) {
Inserter = llvm::make_unique<utils::IncludeInserter>(SM, getLangOpts(),
IncludeStyle);
PP->addPPCallbacks(Inserter->CreatePPCallbacks());
}
}
void PassByValueCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("Ctor");
const auto *ParamDecl = Result.Nodes.getNodeAs<ParmVarDecl>("Param");
const auto *Initializer =
Result.Nodes.getNodeAs<CXXCtorInitializer>("Initializer");
SourceManager &SM = *Result.SourceManager;
// If the parameter is used or anything other than the copy, do not apply
// the changes.
if (!paramReferredExactlyOnce(Ctor, ParamDecl))
return;
// If the parameter is trivial to copy, don't move it. Moving a trivivally
// copyable type will cause a problem with performance-move-const-arg
if (ParamDecl->getType().getNonReferenceType().isTriviallyCopyableType(
*Result.Context))
return;
auto Diag = diag(ParamDecl->getBeginLoc(), "pass by value and use std::move");
// Iterate over all declarations of the constructor.
for (const ParmVarDecl *ParmDecl : collectParamDecls(Ctor, ParamDecl)) {
auto ParamTL = ParmDecl->getTypeSourceInfo()->getTypeLoc();
auto RefTL = ParamTL.getAs<ReferenceTypeLoc>();
// Do not replace if it is already a value, skip.
if (RefTL.isNull())
continue;
TypeLoc ValueTL = RefTL.getPointeeLoc();
auto TypeRange = CharSourceRange::getTokenRange(ParmDecl->getBeginLoc(),
ParamTL.getEndLoc());
std::string ValueStr = Lexer::getSourceText(CharSourceRange::getTokenRange(
ValueTL.getSourceRange()),
SM, getLangOpts())
.str();
ValueStr += ' ';
Diag << FixItHint::CreateReplacement(TypeRange, ValueStr);
}
// Use std::move in the initialization list.
Diag << FixItHint::CreateInsertion(Initializer->getRParenLoc(), ")")
<< FixItHint::CreateInsertion(
Initializer->getLParenLoc().getLocWithOffset(1), "std::move(");
if (auto IncludeFixit = Inserter->CreateIncludeInsertion(
Result.SourceManager->getFileID(Initializer->getSourceLocation()),
"utility",
/*IsAngled=*/true)) {
Diag << *IncludeFixit;
}
}
} // namespace modernize
} // namespace tidy
} // namespace clang
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