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//===--- UnusedParametersCheck.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 "UnusedParametersCheck.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
#include "llvm/ADT/STLExtras.h"
#include <unordered_map>
#include <unordered_set>
using namespace clang::ast_matchers;
namespace clang::tidy::misc {
namespace {
bool isOverrideMethod(const FunctionDecl *Function) {
if (const auto *MD = dyn_cast<CXXMethodDecl>(Function))
return MD->size_overridden_methods() > 0 || MD->hasAttr<OverrideAttr>();
return false;
}
} // namespace
void UnusedParametersCheck::registerMatchers(MatchFinder *Finder) {
Finder->addMatcher(functionDecl(isDefinition(), hasBody(stmt()),
hasAnyParameter(decl()),
unless(hasAttr(attr::Kind::Naked)))
.bind("function"),
this);
}
template <typename T>
static CharSourceRange removeNode(const MatchFinder::MatchResult &Result,
const T *PrevNode, const T *Node,
const T *NextNode) {
if (NextNode)
return CharSourceRange::getCharRange(Node->getBeginLoc(),
NextNode->getBeginLoc());
if (PrevNode)
return CharSourceRange::getTokenRange(
Lexer::getLocForEndOfToken(PrevNode->getEndLoc(), 0,
*Result.SourceManager,
Result.Context->getLangOpts()),
Node->getEndLoc());
return CharSourceRange::getTokenRange(Node->getSourceRange());
}
static FixItHint removeParameter(const MatchFinder::MatchResult &Result,
const FunctionDecl *Function, unsigned Index) {
return FixItHint::CreateRemoval(removeNode(
Result, Index > 0 ? Function->getParamDecl(Index - 1) : nullptr,
Function->getParamDecl(Index),
Index + 1 < Function->getNumParams() ? Function->getParamDecl(Index + 1)
: nullptr));
}
static FixItHint removeArgument(const MatchFinder::MatchResult &Result,
const CallExpr *Call, unsigned Index) {
return FixItHint::CreateRemoval(removeNode(
Result, Index > 0 ? Call->getArg(Index - 1) : nullptr,
Call->getArg(Index),
Index + 1 < Call->getNumArgs() ? Call->getArg(Index + 1) : nullptr));
}
class UnusedParametersCheck::IndexerVisitor
: public RecursiveASTVisitor<IndexerVisitor> {
public:
IndexerVisitor(ASTContext &Ctx) { TraverseAST(Ctx); }
const std::unordered_set<const CallExpr *> &
getFnCalls(const FunctionDecl *Fn) {
return Index[Fn->getCanonicalDecl()].Calls;
}
const std::unordered_set<const DeclRefExpr *> &
getOtherRefs(const FunctionDecl *Fn) {
return Index[Fn->getCanonicalDecl()].OtherRefs;
}
bool shouldTraversePostOrder() const { return true; }
bool WalkUpFromDeclRefExpr(DeclRefExpr *DeclRef) {
if (const auto *Fn = dyn_cast<FunctionDecl>(DeclRef->getDecl())) {
Fn = Fn->getCanonicalDecl();
Index[Fn].OtherRefs.insert(DeclRef);
}
return true;
}
bool WalkUpFromCallExpr(CallExpr *Call) {
if (const auto *Fn =
dyn_cast_or_null<FunctionDecl>(Call->getCalleeDecl())) {
Fn = Fn->getCanonicalDecl();
if (const auto *Ref =
dyn_cast<DeclRefExpr>(Call->getCallee()->IgnoreImplicit())) {
Index[Fn].OtherRefs.erase(Ref);
}
Index[Fn].Calls.insert(Call);
}
return true;
}
private:
struct IndexEntry {
std::unordered_set<const CallExpr *> Calls;
std::unordered_set<const DeclRefExpr *> OtherRefs;
};
std::unordered_map<const FunctionDecl *, IndexEntry> Index;
};
UnusedParametersCheck::~UnusedParametersCheck() = default;
UnusedParametersCheck::UnusedParametersCheck(StringRef Name,
ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
StrictMode(Options.getLocalOrGlobal("StrictMode", false)) {}
void UnusedParametersCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "StrictMode", StrictMode);
}
void UnusedParametersCheck::warnOnUnusedParameter(
const MatchFinder::MatchResult &Result, const FunctionDecl *Function,
unsigned ParamIndex) {
const auto *Param = Function->getParamDecl(ParamIndex);
// Don't bother to diagnose invalid parameters as being unused.
if (Param->isInvalidDecl())
return;
auto MyDiag = diag(Param->getLocation(), "parameter %0 is unused") << Param;
if (!Indexer) {
Indexer = std::make_unique<IndexerVisitor>(*Result.Context);
}
// Cannot remove parameter for non-local functions.
if (Function->isExternallyVisible() ||
!Result.SourceManager->isInMainFile(Function->getLocation()) ||
!Indexer->getOtherRefs(Function).empty() || isOverrideMethod(Function) ||
isLambdaCallOperator(Function)) {
// It is illegal to omit parameter name here in C code, so early-out.
if (!Result.Context->getLangOpts().CPlusPlus)
return;
SourceRange RemovalRange(Param->getLocation());
// Note: We always add a space before the '/*' to not accidentally create
// a '*/*' for pointer types, which doesn't start a comment. clang-format
// will clean this up afterwards.
MyDiag << FixItHint::CreateReplacement(
RemovalRange, (Twine(" /*") + Param->getName() + "*/").str());
return;
}
// Fix all redeclarations.
for (const FunctionDecl *FD : Function->redecls())
if (FD->param_size())
MyDiag << removeParameter(Result, FD, ParamIndex);
// Fix all call sites.
for (const CallExpr *Call : Indexer->getFnCalls(Function))
if (ParamIndex < Call->getNumArgs()) // See PR38055 for example.
MyDiag << removeArgument(Result, Call, ParamIndex);
}
void UnusedParametersCheck::check(const MatchFinder::MatchResult &Result) {
const auto *Function = Result.Nodes.getNodeAs<FunctionDecl>("function");
if (!Function->hasWrittenPrototype() || Function->isTemplateInstantiation())
return;
if (const auto *Method = dyn_cast<CXXMethodDecl>(Function))
if (Method->isLambdaStaticInvoker())
return;
for (unsigned I = 0, E = Function->getNumParams(); I != E; ++I) {
const auto *Param = Function->getParamDecl(I);
if (Param->isUsed() || Param->isReferenced() || !Param->getDeclName() ||
Param->hasAttr<UnusedAttr>())
continue;
// In non-strict mode ignore function definitions with empty bodies
// (constructor initializer counts for non-empty body).
if (StrictMode ||
(Function->getBody()->child_begin() !=
Function->getBody()->child_end()) ||
(isa<CXXConstructorDecl>(Function) &&
cast<CXXConstructorDecl>(Function)->getNumCtorInitializers() > 0))
warnOnUnusedParameter(Result, Function, I);
}
}
} // namespace clang::tidy::misc
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