clang-tools 10.0.0

StrCatAppendCheck.cpp
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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 if (!getLangOpts().CPlusPlus)
46 return;
47 const auto StrCat = functionDecl(hasName("::absl::StrCat"));
48 // The arguments of absl::StrCat are implicitly converted to AlphaNum. This
49 // matches to the arguments because of that behavior.
50 const auto AlphaNum = IgnoringTemporaries(cxxConstructExpr(
51 argumentCountIs(1), hasType(cxxRecordDecl(hasName("::absl::AlphaNum"))),
52 hasArgument(0, ignoringImpCasts(declRefExpr(to(equalsBoundNode("LHS")),
53 expr().bind("Arg0"))))));
54
55 const auto HasAnotherReferenceToLhs =
56 callExpr(hasAnyArgument(expr(hasDescendant(declRefExpr(
57 to(equalsBoundNode("LHS")), unless(equalsBoundNode("Arg0")))))));
58
59 // Now look for calls to operator= with an object on the LHS and a call to
60 // StrCat on the RHS. The first argument of the StrCat call should be the same
61 // as the LHS. Ignore calls from template instantiations.
62 Finder->addMatcher(
63 cxxOperatorCallExpr(
64 unless(isInTemplateInstantiation()), hasOverloadedOperatorName("="),
65 hasArgument(0, declRefExpr(to(decl().bind("LHS")))),
66 hasArgument(1, IgnoringTemporaries(
67 callExpr(callee(StrCat), hasArgument(0, AlphaNum),
68 unless(HasAnotherReferenceToLhs))
69 .bind("Call"))))
70 .bind("Op"),
71 this);
72 }
73
74 void StrCatAppendCheck::check(const MatchFinder::MatchResult &Result) {
75 const auto *Op = Result.Nodes.getNodeAs<CXXOperatorCallExpr>("Op");
76 const auto *Call = Result.Nodes.getNodeAs<CallExpr>("Call");
77 assert(Op != nullptr && Call != nullptr && "Matcher does not work as expected");
78
79 // Handles the case 'x = absl::StrCat(x)', which has no effect.
80 if (Call->getNumArgs() == 1) {
81 diag(Op->getBeginLoc(), "call to 'absl::StrCat' has no effect");
82 return;
83 }
84
85 // Emit a warning and emit fixits to go from
86 // x = absl::StrCat(x, ...)
87 // to
88 // absl::StrAppend(&x, ...)
89 diag(Op->getBeginLoc(),
90 "call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a "
91 "string to avoid a performance penalty")
92 << FixItHint::CreateReplacement(
93 CharSourceRange::getTokenRange(Op->getBeginLoc(),
94 Call->getCallee()->getEndLoc()),
95 "absl::StrAppend")
96 << FixItHint::CreateInsertion(Call->getArg(0)->getBeginLoc(), "&");
97 }
98
99 } // namespace abseil
100 } // namespace tidy
101 } // namespace clang
clang::ast_matchers
Definition: AbseilMatcher.h:14
clang::clangd::getTokenRange
llvm::Optional< Range > getTokenRange(const SourceManager &SM, const LangOptions &LangOpts, SourceLocation TokLoc)
Returns the taken range at TokLoc.
Definition: SourceCode.cpp:227
Builder
CodeCompletionBuilder Builder
Definition: CodeCompletionStringsTests.cpp:35
clang
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Definition: ApplyReplacements.h:27
E
const Expr * E
Definition: AvoidBindCheck.cpp:82
StrCatAppendCheck.h
clang::tidy::readability::AST_MATCHER_P
AST_MATCHER_P(CXXMethodDecl, hasCanonicalDecl, ast_matchers::internal::Matcher< CXXMethodDecl >, InnerMatcher)
Definition: ConvertMemberFunctionsToStatic.cpp:52