clang-tools  10.0.0
RedundantStrcatCallsCheck.cpp
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1 //===--- RedundantStrcatCallsCheck.cpp - clang-tidy------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 
13 using namespace clang::ast_matchers;
14 
15 namespace clang {
16 namespace tidy {
17 namespace abseil {
18 
19 // TODO: Features to add to the check:
20 // - Make it work if num_args > 26.
21 // - Remove empty literal string arguments.
22 // - Collapse consecutive literal string arguments into one (remove the ,).
23 // - Replace StrCat(a + b) -> StrCat(a, b) if a or b are strings.
24 // - Make it work in macros if the outer and inner StrCats are both in the
25 // argument.
26 
27 void RedundantStrcatCallsCheck::registerMatchers(MatchFinder* Finder) {
28  if (!getLangOpts().CPlusPlus)
29  return;
30  const auto CallToStrcat =
31  callExpr(callee(functionDecl(hasName("::absl::StrCat"))));
32  const auto CallToStrappend =
33  callExpr(callee(functionDecl(hasName("::absl::StrAppend"))));
34  // Do not match StrCat() calls that are descendants of other StrCat calls.
35  // Those are handled on the ancestor call.
36  const auto CallToEither = callExpr(
37  callee(functionDecl(hasAnyName("::absl::StrCat", "::absl::StrAppend"))));
38  Finder->addMatcher(
39  callExpr(CallToStrcat, unless(hasAncestor(CallToEither))).bind("StrCat"),
40  this);
41  Finder->addMatcher(CallToStrappend.bind("StrAppend"), this);
42 }
43 
44 namespace {
45 
46 struct StrCatCheckResult {
47  int NumCalls = 0;
48  std::vector<FixItHint> Hints;
49 };
50 
51 void RemoveCallLeaveArgs(const CallExpr* Call, StrCatCheckResult* CheckResult) {
52  // Remove 'Foo('
53  CheckResult->Hints.push_back(
54  FixItHint::CreateRemoval(CharSourceRange::getCharRange(
55  Call->getBeginLoc(), Call->getArg(0)->getBeginLoc())));
56  // Remove the ')'
57  CheckResult->Hints.push_back(
58  FixItHint::CreateRemoval(CharSourceRange::getCharRange(
59  Call->getRParenLoc(), Call->getEndLoc().getLocWithOffset(1))));
60 }
61 
62 const clang::CallExpr* ProcessArgument(const Expr* Arg,
63  const MatchFinder::MatchResult& Result,
64  StrCatCheckResult* CheckResult) {
65  const auto IsAlphanum = hasDeclaration(cxxMethodDecl(hasName("AlphaNum")));
66  static const auto* const Strcat = new auto(hasName("::absl::StrCat"));
67  const auto IsStrcat = cxxBindTemporaryExpr(
68  has(callExpr(callee(functionDecl(*Strcat))).bind("StrCat")));
69  if (const auto* SubStrcatCall = selectFirst<const CallExpr>(
70  "StrCat",
71  match(stmt(anyOf(
72  cxxConstructExpr(IsAlphanum, hasArgument(0, IsStrcat)),
73  IsStrcat)),
74  *Arg->IgnoreParenImpCasts(), *Result.Context))) {
75  RemoveCallLeaveArgs(SubStrcatCall, CheckResult);
76  return SubStrcatCall;
77  }
78  return nullptr;
79 }
80 
81 StrCatCheckResult ProcessCall(const CallExpr* RootCall, bool IsAppend,
82  const MatchFinder::MatchResult& Result) {
83  StrCatCheckResult CheckResult;
84  std::deque<const CallExpr*> CallsToProcess = {RootCall};
85 
86  while (!CallsToProcess.empty()) {
87  ++CheckResult.NumCalls;
88 
89  const CallExpr* CallExpr = CallsToProcess.front();
90  CallsToProcess.pop_front();
91 
92  int StartArg = CallExpr == RootCall && IsAppend;
93  for (const auto *Arg : CallExpr->arguments()) {
94  if (StartArg-- > 0)
95  continue;
96  if (const clang::CallExpr* Sub =
97  ProcessArgument(Arg, Result, &CheckResult)) {
98  CallsToProcess.push_back(Sub);
99  }
100  }
101  }
102  return CheckResult;
103 }
104 } // namespace
105 
106 void RedundantStrcatCallsCheck::check(const MatchFinder::MatchResult& Result) {
107  bool IsAppend;
108 
109  const CallExpr* RootCall;
110  if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrCat")))
111  IsAppend = false;
112  else if ((RootCall = Result.Nodes.getNodeAs<CallExpr>("StrAppend")))
113  IsAppend = true;
114  else
115  return;
116 
117  if (RootCall->getBeginLoc().isMacroID()) {
118  // Ignore calls within macros.
119  // In many cases the outer StrCat part of the macro and the inner StrCat is
120  // a macro argument. Removing the inner StrCat() converts one macro
121  // argument into many.
122  return;
123  }
124 
125  const StrCatCheckResult CheckResult =
126  ProcessCall(RootCall, IsAppend, Result);
127  if (CheckResult.NumCalls == 1) {
128  // Just one call, so nothing to fix.
129  return;
130  }
131 
132  diag(RootCall->getBeginLoc(),
133  "multiple calls to 'absl::StrCat' can be flattened into a single call")
134  << CheckResult.Hints;
135 }
136 
137 } // namespace abseil
138 } // namespace tidy
139 } // namespace clang
std::vector< std::string > match(const SymbolIndex &I, const FuzzyFindRequest &Req, bool *Incomplete)
Definition: TestIndex.cpp:94
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
std::vector< FixItHint > Hints