clang-tools  14.0.0git
StrCatAppendCheck.cpp
Go to the documentation of this file.
1 //===--- StrCatAppendCheck.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 
9 #include "StrCatAppendCheck.h"
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 namespace {
20 // Skips any combination of temporary materialization, temporary binding and
21 // implicit casting.
22 AST_MATCHER_P(Stmt, IgnoringTemporaries, ast_matchers::internal::Matcher<Stmt>,
23  InnerMatcher) {
24  const Stmt *E = &Node;
25  while (true) {
26  if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))
27  E = MTE->getSubExpr();
28  if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))
29  E = BTE->getSubExpr();
30  if (const auto *ICE = dyn_cast<ImplicitCastExpr>(E))
31  E = ICE->getSubExpr();
32  else
33  break;
34  }
35 
36  return InnerMatcher.matches(*E, Finder, Builder);
37 }
38 
39 } // namespace
40 
41 // TODO: str += StrCat(...)
42 // str.append(StrCat(...))
43 
44 void StrCatAppendCheck::registerMatchers(MatchFinder *Finder) {
45  const auto StrCat = functionDecl(hasName("::absl::StrCat"));
46  // The arguments of absl::StrCat are implicitly converted to AlphaNum. This
47  // matches to the arguments because of that behavior.
48  const auto AlphaNum = IgnoringTemporaries(cxxConstructExpr(
49  argumentCountIs(1), hasType(cxxRecordDecl(hasName("::absl::AlphaNum"))),
50  hasArgument(0, ignoringImpCasts(declRefExpr(to(equalsBoundNode("LHS")),
51  expr().bind("Arg0"))))));
52 
53  const auto HasAnotherReferenceToLhs =
54  callExpr(hasAnyArgument(expr(hasDescendant(declRefExpr(
55  to(equalsBoundNode("LHS")), unless(equalsBoundNode("Arg0")))))));
56 
57  // Now look for calls to operator= with an object on the LHS and a call to
58  // StrCat on the RHS. The first argument of the StrCat call should be the same
59  // as the LHS. Ignore calls from template instantiations.
60  Finder->addMatcher(
61  traverse(TK_AsIs,
62  cxxOperatorCallExpr(
63  unless(isInTemplateInstantiation()),
64  hasOverloadedOperatorName("="),
65  hasArgument(0, declRefExpr(to(decl().bind("LHS")))),
66  hasArgument(
67  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
E
const Expr * E
Definition: AvoidBindCheck.cpp:88
clang::ast_matchers
Definition: AbseilMatcher.h:14
Builder
CodeCompletionBuilder Builder
Definition: CodeCompletionStringsTests.cpp:36
clang::clangd::check
bool check(llvm::StringRef File, llvm::function_ref< bool(const Position &)> ShouldCheckLine, const ThreadsafeFS &TFS, const ClangdLSPServer::Options &Opts, bool EnableCodeCompletion)
Definition: Check.cpp:258
StrCatAppendCheck.h
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
clang::tidy::bugprone::AST_MATCHER_P
AST_MATCHER_P(FunctionDecl, parameterCountGE, unsigned, N)
Matches functions that have at least the specified amount of parameters.
Definition: EasilySwappableParametersCheck.cpp:1888