clang-tools  8.0.0
StrCatAppendCheck.cpp
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1 //===--- StrCatAppendCheck.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 "StrCatAppendCheck.h"
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 namespace {
21 // Skips any combination of temporary materialization, temporary binding and
22 // implicit casting.
23 AST_MATCHER_P(Stmt, IgnoringTemporaries, ast_matchers::internal::Matcher<Stmt>,
24  InnerMatcher) {
25  const Stmt *E = &Node;
26  while (true) {
27  if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))
28  E = MTE->getTemporary();
29  if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))
30  E = BTE->getSubExpr();
31  if (const auto *ICE = dyn_cast<ImplicitCastExpr>(E))
32  E = ICE->getSubExpr();
33  else
34  break;
35  }
36 
37  return InnerMatcher.matches(*E, Finder, Builder);
38 }
39 
40 } // namespace
41 
42 // TODO: str += StrCat(...)
43 // str.append(StrCat(...))
44 
45 void StrCatAppendCheck::registerMatchers(MatchFinder *Finder) {
46  if (!getLangOpts().CPlusPlus)
47  return;
48  const auto StrCat = functionDecl(hasName("::absl::StrCat"));
49  // The arguments of absl::StrCat are implicitly converted to AlphaNum. This
50  // matches to the arguments because of that behavior.
51  const auto AlphaNum = IgnoringTemporaries(cxxConstructExpr(
52  argumentCountIs(1), hasType(cxxRecordDecl(hasName("::absl::AlphaNum"))),
53  hasArgument(0, ignoringImpCasts(declRefExpr(to(equalsBoundNode("LHS")),
54  expr().bind("Arg0"))))));
55 
56  const auto HasAnotherReferenceToLhs =
57  callExpr(hasAnyArgument(expr(hasDescendant(declRefExpr(
58  to(equalsBoundNode("LHS")), unless(equalsBoundNode("Arg0")))))));
59 
60  // Now look for calls to operator= with an object on the LHS and a call to
61  // StrCat on the RHS. The first argument of the StrCat call should be the same
62  // as the LHS. Ignore calls from template instantiations.
63  Finder->addMatcher(
64  cxxOperatorCallExpr(
65  unless(isInTemplateInstantiation()), hasOverloadedOperatorName("="),
66  hasArgument(0, declRefExpr(to(decl().bind("LHS")))),
67  hasArgument(1, IgnoringTemporaries(
68  callExpr(callee(StrCat), hasArgument(0, AlphaNum),
69  unless(HasAnotherReferenceToLhs))
70  .bind("Call"))))
71  .bind("Op"),
72  this);
73 }
74 
75 void StrCatAppendCheck::check(const MatchFinder::MatchResult &Result) {
76  const auto *Op = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("Op");
77  const auto *Call = Result.Nodes.getNodeAs<CallExpr>("Call");
78  assert(Op != nullptr && Call != nullptr && "Matcher does not work as expected");
79 
80  // Handles the case 'x = absl::StrCat(x)', which has no effect.
81  if (Call->getNumArgs() == 1) {
82  diag(Op->getBeginLoc(), "call to 'absl::StrCat' has no effect");
83  return;
84  }
85 
86  // Emit a warning and emit fixits to go from
87  // x = absl::StrCat(x, ...)
88  // to
89  // absl::StrAppend(&x, ...)
90  diag(Op->getBeginLoc(),
91  "call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a "
92  "string to avoid a performance penalty")
93  << FixItHint::CreateReplacement(
94  CharSourceRange::getTokenRange(Op->getBeginLoc(),
95  Call->getCallee()->getEndLoc()),
96  "absl::StrAppend")
97  << FixItHint::CreateInsertion(Call->getArg(0)->getBeginLoc(), "&");
98 }
99 
100 } // namespace abseil
101 } // namespace tidy
102 } // namespace clang
llvm::Optional< llvm::Expected< tooling::AtomicChanges > > Result
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
AST_MATCHER_P(FunctionDecl, throws, internal::Matcher< Type >, InnerMatcher)