clang-tools  8.0.0
RedundantStrcatCallsCheck.cpp
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1 //===--- RedundantStrcatCallsCheck.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 
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace abseil {
19 
20 // TODO: Features to add to the check:
21 // - Make it work if num_args > 26.
22 // - Remove empty literal string arguments.
23 // - Collapse consecutive literal string arguments into one (remove the ,).
24 // - Replace StrCat(a + b) -> StrCat(a, b) if a or b are strings.
25 // - Make it work in macros if the outer and inner StrCats are both in the
26 // argument.
27 
28 void RedundantStrcatCallsCheck::registerMatchers(MatchFinder* Finder) {
29  if (!getLangOpts().CPlusPlus)
30  return;
31  const auto CallToStrcat =
32  callExpr(callee(functionDecl(hasName("::absl::StrCat"))));
33  const auto CallToStrappend =
34  callExpr(callee(functionDecl(hasName("::absl::StrAppend"))));
35  // Do not match StrCat() calls that are descendants of other StrCat calls.
36  // Those are handled on the ancestor call.
37  const auto CallToEither = callExpr(
38  callee(functionDecl(hasAnyName("::absl::StrCat", "::absl::StrAppend"))));
39  Finder->addMatcher(
40  callExpr(CallToStrcat, unless(hasAncestor(CallToEither))).bind("StrCat"),
41  this);
42  Finder->addMatcher(CallToStrappend.bind("StrAppend"), this);
43 }
44 
45 namespace {
46 
47 struct StrCatCheckResult {
48  int NumCalls = 0;
49  std::vector<FixItHint> Hints;
50 };
51 
52 void RemoveCallLeaveArgs(const CallExpr* Call, StrCatCheckResult* CheckResult) {
53  // Remove 'Foo('
54  CheckResult->Hints.push_back(
55  FixItHint::CreateRemoval(CharSourceRange::getCharRange(
56  Call->getBeginLoc(), Call->getArg(0)->getBeginLoc())));
57  // Remove the ')'
58  CheckResult->Hints.push_back(
59  FixItHint::CreateRemoval(CharSourceRange::getCharRange(
60  Call->getRParenLoc(), Call->getEndLoc().getLocWithOffset(1))));
61 }
62 
63 const clang::CallExpr* ProcessArgument(const Expr* Arg,
64  const MatchFinder::MatchResult& Result,
65  StrCatCheckResult* CheckResult) {
66  const auto IsAlphanum = hasDeclaration(cxxMethodDecl(hasName("AlphaNum")));
67  static const auto* const Strcat = new auto(hasName("::absl::StrCat"));
68  const auto IsStrcat = cxxBindTemporaryExpr(
69  has(callExpr(callee(functionDecl(*Strcat))).bind("StrCat")));
70  if (const auto* SubStrcatCall = selectFirst<const CallExpr>(
71  "StrCat",
72  match(stmt(anyOf(
73  cxxConstructExpr(IsAlphanum, hasArgument(0, IsStrcat)),
74  IsStrcat)),
75  *Arg->IgnoreParenImpCasts(), *Result.Context))) {
76  RemoveCallLeaveArgs(SubStrcatCall, CheckResult);
77  return SubStrcatCall;
78  }
79  return nullptr;
80 }
81 
82 StrCatCheckResult ProcessCall(const CallExpr* RootCall, bool IsAppend,
83  const MatchFinder::MatchResult& Result) {
84  StrCatCheckResult CheckResult;
85  std::deque<const CallExpr*> CallsToProcess = {RootCall};
86 
87  while (!CallsToProcess.empty()) {
88  ++CheckResult.NumCalls;
89 
90  const CallExpr* CallExpr = CallsToProcess.front();
91  CallsToProcess.pop_front();
92 
93  int StartArg = CallExpr == RootCall && IsAppend;
94  for (const auto *Arg : CallExpr->arguments()) {
95  if (StartArg-- > 0)
96  continue;
97  if (const clang::CallExpr* Sub =
98  ProcessArgument(Arg, Result, &CheckResult)) {
99  CallsToProcess.push_back(Sub);
100  }
101  }
102  }
103  return CheckResult;
104 }
105 } // namespace
106 
107 void RedundantStrcatCallsCheck::check(const MatchFinder::MatchResult& Result) {
108  bool IsAppend;
109 
110  const CallExpr* RootCall;
111  if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrCat")))
112  IsAppend = false;
113  else if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrAppend")))
114  IsAppend = true;
115  else
116  return;
117 
118  if (RootCall->getBeginLoc().isMacroID()) {
119  // Ignore calls within macros.
120  // In many cases the outer StrCat part of the macro and the inner StrCat is
121  // a macro argument. Removing the inner StrCat() converts one macro
122  // argument into many.
123  return;
124  }
125 
126  const StrCatCheckResult CheckResult =
127  ProcessCall(RootCall, IsAppend, Result);
128  if (CheckResult.NumCalls == 1) {
129  // Just one call, so nothing to fix.
130  return;
131  }
132 
133  diag(RootCall->getBeginLoc(),
134  "multiple calls to 'absl::StrCat' can be flattened into a single call")
135  << CheckResult.Hints;
136 }
137 
138 } // namespace abseil
139 } // namespace tidy
140 } // namespace clang
llvm::Optional< llvm::Expected< tooling::AtomicChanges > > Result
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
std::vector< FixItHint > Hints