clang-tools  3.8.0
UnusedParametersCheck.cpp
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1 //===--- UnusedParametersCheck.cpp - clang-tidy----------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "UnusedParametersCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Lex/Lexer.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 
20 void UnusedParametersCheck::registerMatchers(MatchFinder *Finder) {
21  Finder->addMatcher(functionDecl().bind("function"), this);
22 }
23 
24 template <typename T>
25 static CharSourceRange removeNode(const MatchFinder::MatchResult &Result,
26  const T *PrevNode, const T *Node,
27  const T *NextNode) {
28  if (NextNode)
29  return CharSourceRange::getCharRange(Node->getLocStart(),
30  NextNode->getLocStart());
31 
32  if (PrevNode)
33  return CharSourceRange::getTokenRange(
34  Lexer::getLocForEndOfToken(PrevNode->getLocEnd(), 0,
35  *Result.SourceManager,
36  Result.Context->getLangOpts()),
37  Node->getLocEnd());
38 
39  return CharSourceRange::getTokenRange(Node->getSourceRange());
40 }
41 
42 static FixItHint removeParameter(const MatchFinder::MatchResult &Result,
43  const FunctionDecl *Function, unsigned Index) {
44  return FixItHint::CreateRemoval(removeNode(
45  Result, Index > 0 ? Function->getParamDecl(Index - 1) : nullptr,
46  Function->getParamDecl(Index),
47  Index + 1 < Function->getNumParams() ? Function->getParamDecl(Index + 1)
48  : nullptr));
49 }
50 
51 static FixItHint removeArgument(const MatchFinder::MatchResult &Result,
52  const CallExpr *Call, unsigned Index) {
53  return FixItHint::CreateRemoval(removeNode(
54  Result, Index > 0 ? Call->getArg(Index - 1) : nullptr,
55  Call->getArg(Index),
56  Index + 1 < Call->getNumArgs() ? Call->getArg(Index + 1) : nullptr));
57 }
58 
59 void UnusedParametersCheck::warnOnUnusedParameter(
60  const MatchFinder::MatchResult &Result, const FunctionDecl *Function,
61  unsigned ParamIndex) {
62  const auto *Param = Function->getParamDecl(ParamIndex);
63  auto MyDiag = diag(Param->getLocation(), "parameter '%0' is unused")
64  << Param->getName();
65 
66  auto UsedByRef = [&] {
67  return !ast_matchers::match(
68  decl(hasDescendant(
69  declRefExpr(to(equalsNode(Function)),
70  unless(hasAncestor(
71  callExpr(callee(equalsNode(Function)))))))),
72  *Result.Context->getTranslationUnitDecl(), *Result.Context)
73  .empty();
74  };
75 
76  // Comment out parameter name for non-local functions.
77  if (Function->isExternallyVisible() ||
78  !Result.SourceManager->isInMainFile(Function->getLocation()) ||
79  UsedByRef()) {
80  SourceRange RemovalRange(Param->getLocation(), Param->getLocEnd());
81  // Note: We always add a space before the '/*' to not accidentally create a
82  // '*/*' for pointer types, which doesn't start a comment. clang-format will
83  // clean this up afterwards.
84  MyDiag << FixItHint::CreateReplacement(
85  RemovalRange, (Twine(" /*") + Param->getName() + "*/").str());
86  return;
87  }
88 
89  // Fix all redeclarations.
90  for (const FunctionDecl *FD : Function->redecls())
91  if (FD->param_size())
92  MyDiag << removeParameter(Result, FD, ParamIndex);
93 
94  // Fix all call sites.
95  auto CallMatches = ast_matchers::match(
96  decl(forEachDescendant(
97  callExpr(callee(functionDecl(equalsNode(Function)))).bind("x"))),
98  *Result.Context->getTranslationUnitDecl(), *Result.Context);
99  for (const auto &Match : CallMatches)
100  MyDiag << removeArgument(Result, Match.getNodeAs<CallExpr>("x"),
101  ParamIndex);
102 }
103 
104 void UnusedParametersCheck::check(const MatchFinder::MatchResult &Result) {
105  const auto *Function = Result.Nodes.getNodeAs<FunctionDecl>("function");
106  if (!Function->doesThisDeclarationHaveABody() ||
107  !Function->hasWrittenPrototype())
108  return;
109  if (const auto *Method = dyn_cast<CXXMethodDecl>(Function))
110  if (Method->isLambdaStaticInvoker())
111  return;
112  for (unsigned i = 0, e = Function->getNumParams(); i != e; ++i) {
113  const auto *Param = Function->getParamDecl(i);
114  if (Param->isUsed() || Param->isReferenced() || !Param->getDeclName() ||
115  Param->hasAttr<UnusedAttr>())
116  continue;
117  warnOnUnusedParameter(Result, Function, i);
118  }
119 }
120 
121 } // namespace tidy
122 } // namespace clang
std::unique_ptr< ast_matchers::MatchFinder > Finder
Definition: ClangTidy.cpp:188
static FixItHint removeArgument(const MatchFinder::MatchResult &Result, const CallExpr *Call, unsigned Index)
static FixItHint removeParameter(const MatchFinder::MatchResult &Result, const FunctionDecl *Function, unsigned Index)
static CharSourceRange removeNode(const MatchFinder::MatchResult &Result, const T *PrevNode, const T *Node, const T *NextNode)
const NamedDecl * Result
Definition: USRFinder.cpp:121