clang-tools  10.0.0git
StringConstructorCheck.cpp
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1 //===--- StringConstructorCheck.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 #include "clang/Tooling/FixIt.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace bugprone {
19 
20 namespace {
21 AST_MATCHER_P(IntegerLiteral, isBiggerThan, unsigned, N) {
22  return Node.getValue().getZExtValue() > N;
23 }
24 } // namespace
25 
26 StringConstructorCheck::StringConstructorCheck(StringRef Name,
27  ClangTidyContext *Context)
28  : ClangTidyCheck(Name, Context),
29  WarnOnLargeLength(Options.get("WarnOnLargeLength", 1) != 0),
30  LargeLengthThreshold(Options.get("LargeLengthThreshold", 0x800000)) {}
31 
33  Options.store(Opts, "WarnOnLargeLength", WarnOnLargeLength);
34  Options.store(Opts, "LargeLengthThreshold", LargeLengthThreshold);
35 }
36 
37 void StringConstructorCheck::registerMatchers(MatchFinder *Finder) {
38  if (!getLangOpts().CPlusPlus)
39  return;
40 
41  const auto ZeroExpr = expr(ignoringParenImpCasts(integerLiteral(equals(0))));
42  const auto CharExpr = expr(ignoringParenImpCasts(characterLiteral()));
43  const auto NegativeExpr = expr(ignoringParenImpCasts(
44  unaryOperator(hasOperatorName("-"),
45  hasUnaryOperand(integerLiteral(unless(equals(0)))))));
46  const auto LargeLengthExpr = expr(ignoringParenImpCasts(
47  integerLiteral(isBiggerThan(LargeLengthThreshold))));
48  const auto CharPtrType = type(anyOf(pointerType(), arrayType()));
49 
50  // Match a string-literal; even through a declaration with initializer.
51  const auto BoundStringLiteral = stringLiteral().bind("str");
52  const auto ConstStrLiteralDecl = varDecl(
53  isDefinition(), hasType(constantArrayType()), hasType(isConstQualified()),
54  hasInitializer(ignoringParenImpCasts(BoundStringLiteral)));
55  const auto ConstPtrStrLiteralDecl = varDecl(
56  isDefinition(),
57  hasType(pointerType(pointee(isAnyCharacter(), isConstQualified()))),
58  hasInitializer(ignoringParenImpCasts(BoundStringLiteral)));
59  const auto ConstStrLiteral = expr(ignoringParenImpCasts(anyOf(
60  BoundStringLiteral, declRefExpr(hasDeclaration(anyOf(
61  ConstPtrStrLiteralDecl, ConstStrLiteralDecl))))));
62 
63  // Check the fill constructor. Fills the string with n consecutive copies of
64  // character c. [i.e string(size_t n, char c);].
65  Finder->addMatcher(
66  cxxConstructExpr(
67  hasDeclaration(cxxMethodDecl(hasName("basic_string"))),
68  hasArgument(0, hasType(qualType(isInteger()))),
69  hasArgument(1, hasType(qualType(isInteger()))),
70  anyOf(
71  // Detect the expression: string('x', 40);
72  hasArgument(0, CharExpr.bind("swapped-parameter")),
73  // Detect the expression: string(0, ...);
74  hasArgument(0, ZeroExpr.bind("empty-string")),
75  // Detect the expression: string(-4, ...);
76  hasArgument(0, NegativeExpr.bind("negative-length")),
77  // Detect the expression: string(0x1234567, ...);
78  hasArgument(0, LargeLengthExpr.bind("large-length"))))
79  .bind("constructor"),
80  this);
81 
82  // Check the literal string constructor with char pointer and length
83  // parameters. [i.e. string (const char* s, size_t n);]
84  Finder->addMatcher(
85  cxxConstructExpr(
86  hasDeclaration(cxxMethodDecl(hasName("basic_string"))),
87  hasArgument(0, hasType(CharPtrType)),
88  hasArgument(1, hasType(isInteger())),
89  anyOf(
90  // Detect the expression: string("...", 0);
91  hasArgument(1, ZeroExpr.bind("empty-string")),
92  // Detect the expression: string("...", -4);
93  hasArgument(1, NegativeExpr.bind("negative-length")),
94  // Detect the expression: string("lit", 0x1234567);
95  hasArgument(1, LargeLengthExpr.bind("large-length")),
96  // Detect the expression: string("lit", 5)
97  allOf(hasArgument(0, ConstStrLiteral.bind("literal-with-length")),
98  hasArgument(1, ignoringParenImpCasts(
99  integerLiteral().bind("int"))))))
100  .bind("constructor"),
101  this);
102 
103  // Check the literal string constructor with char pointer.
104  // [i.e. string (const char* s);]
105  Finder->addMatcher(
106  cxxConstructExpr(hasDeclaration(cxxMethodDecl(hasName("basic_string"))),
107  hasArgument(0, expr().bind("from-ptr")),
108  hasArgument(1, unless(hasType(isInteger()))))
109  .bind("constructor"),
110  this);
111 }
112 
113 void StringConstructorCheck::check(const MatchFinder::MatchResult &Result) {
114  const ASTContext &Ctx = *Result.Context;
115  const auto *E = Result.Nodes.getNodeAs<CXXConstructExpr>("constructor");
116  assert(E && "missing constructor expression");
117  SourceLocation Loc = E->getBeginLoc();
118 
119  if (Result.Nodes.getNodeAs<Expr>("swapped-parameter")) {
120  const Expr *P0 = E->getArg(0);
121  const Expr *P1 = E->getArg(1);
122  diag(Loc, "string constructor parameters are probably swapped;"
123  " expecting string(count, character)")
124  << tooling::fixit::createReplacement(*P0, *P1, Ctx)
125  << tooling::fixit::createReplacement(*P1, *P0, Ctx);
126  } else if (Result.Nodes.getNodeAs<Expr>("empty-string")) {
127  diag(Loc, "constructor creating an empty string");
128  } else if (Result.Nodes.getNodeAs<Expr>("negative-length")) {
129  diag(Loc, "negative value used as length parameter");
130  } else if (Result.Nodes.getNodeAs<Expr>("large-length")) {
131  if (WarnOnLargeLength)
132  diag(Loc, "suspicious large length parameter");
133  } else if (Result.Nodes.getNodeAs<Expr>("literal-with-length")) {
134  const auto *Str = Result.Nodes.getNodeAs<StringLiteral>("str");
135  const auto *Lit = Result.Nodes.getNodeAs<IntegerLiteral>("int");
136  if (Lit->getValue().ugt(Str->getLength())) {
137  diag(Loc, "length is bigger than string literal size");
138  }
139  } else if (const auto *Ptr = Result.Nodes.getNodeAs<Expr>("from-ptr")) {
140  Expr::EvalResult ConstPtr;
141  if (!Ptr->isInstantiationDependent() &&
142  Ptr->EvaluateAsRValue(ConstPtr, Ctx) &&
143  ((ConstPtr.Val.isInt() && ConstPtr.Val.getInt().isNullValue()) ||
144  (ConstPtr.Val.isLValue() && ConstPtr.Val.isNullPointer()))) {
145  diag(Loc, "constructing string from nullptr is undefined behaviour");
146  }
147  }
148 }
149 
150 } // namespace bugprone
151 } // namespace tidy
152 } // namespace clang
SourceLocation Loc
&#39;#&#39; location in the include directive
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
Base class for all clang-tidy checks.
const LangOptions & getLangOpts() const
Returns the language options from the context.
Context Ctx
void store(ClangTidyOptions::OptionMap &Options, StringRef LocalName, StringRef Value) const
Stores an option with the check-local name LocalName with string value Value to Options.
static constexpr llvm::StringLiteral Name
std::map< std::string, std::string > OptionMap
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
const Expr * E
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check&#39;s name.
AST_MATCHER_P(CXXMethodDecl, hasCanonicalDecl, ast_matchers::internal::Matcher< CXXMethodDecl >, InnerMatcher)