1//===- CallDescription.h - function/method call matching       --*- C++ -*-===//
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/// \file This file defines a generic mechanism for matching for function and
10/// method calls of C, C++, and Objective-C languages. Instances of these
11/// classes are frequently used together with the CallEvent classes.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CALLDESCRIPTION_H
16#define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CALLDESCRIPTION_H
17
18#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
19#include "llvm/ADT/ArrayRef.h"
20#include "llvm/Support/Compiler.h"
21#include <optional>
22#include <vector>
23
24namespace clang {
25class IdentifierInfo;
26} // namespace clang
27
28namespace clang {
29namespace ento {
30
31enum CallDescriptionFlags : unsigned {
32  CDF_None = 0,
33
34  /// Describes a C standard function that is sometimes implemented as a macro
35  /// that expands to a compiler builtin with some __builtin prefix.
36  /// The builtin may as well have a few extra arguments on top of the requested
37  /// number of arguments.
38  CDF_MaybeBuiltin = 1 << 0,
39};
40
41/// This class represents a description of a function call using the number of
42/// arguments and the name of the function.
43class CallDescription {
44  friend class CallEvent;
45  using MaybeCount = std::optional<unsigned>;
46
47  mutable std::optional<const IdentifierInfo *> II;
48  // The list of the qualified names used to identify the specified CallEvent,
49  // e.g. "{a, b}" represent the qualified names, like "a::b".
50  std::vector<std::string> QualifiedName;
51  MaybeCount RequiredArgs;
52  MaybeCount RequiredParams;
53  int Flags;
54
55public:
56  /// Constructs a CallDescription object.
57  ///
58  /// @param QualifiedName The list of the name qualifiers of the function that
59  /// will be matched. The user is allowed to skip any of the qualifiers.
60  /// For example, {"std", "basic_string", "c_str"} would match both
61  /// std::basic_string<...>::c_str() and std::__1::basic_string<...>::c_str().
62  ///
63  /// @param RequiredArgs The number of arguments that is expected to match a
64  /// call. Omit this parameter to match every occurrence of call with a given
65  /// name regardless the number of arguments.
66  CallDescription(CallDescriptionFlags Flags, ArrayRef<StringRef> QualifiedName,
67                  MaybeCount RequiredArgs = std::nullopt,
68                  MaybeCount RequiredParams = std::nullopt);
69
70  /// Construct a CallDescription with default flags.
71  CallDescription(ArrayRef<StringRef> QualifiedName,
72                  MaybeCount RequiredArgs = std::nullopt,
73                  MaybeCount RequiredParams = std::nullopt);
74
75  CallDescription(std::nullptr_t) = delete;
76
77  /// Get the name of the function that this object matches.
78  StringRef getFunctionName() const { return QualifiedName.back(); }
79
80  /// Get the qualified name parts in reversed order.
81  /// E.g. { "std", "vector", "data" } -> "vector", "std"
82  auto begin_qualified_name_parts() const {
83    return std::next(QualifiedName.rbegin());
84  }
85  auto end_qualified_name_parts() const { return QualifiedName.rend(); }
86
87  /// It's false, if and only if we expect a single identifier, such as
88  /// `getenv`. It's true for `std::swap`, or `my::detail::container::data`.
89  bool hasQualifiedNameParts() const { return QualifiedName.size() > 1; }
90
91  /// @name Matching CallDescriptions against a CallEvent
92  /// @{
93
94  /// Returns true if the CallEvent is a call to a function that matches
95  /// the CallDescription.
96  ///
97  /// \note This function is not intended to be used to match Obj-C method
98  /// calls.
99  bool matches(const CallEvent &Call) const;
100
101  /// Returns true whether the CallEvent matches on any of the CallDescriptions
102  /// supplied.
103  ///
104  /// \note This function is not intended to be used to match Obj-C method
105  /// calls.
106  friend bool matchesAny(const CallEvent &Call, const CallDescription &CD1) {
107    return CD1.matches(Call);
108  }
109
110  /// \copydoc clang::ento::CallDescription::matchesAny(const CallEvent &, const CallDescription &)
111  template <typename... Ts>
112  friend bool matchesAny(const CallEvent &Call, const CallDescription &CD1,
113                         const Ts &...CDs) {
114    return CD1.matches(Call) || matchesAny(Call, CDs...);
115  }
116  /// @}
117
118  /// @name Matching CallDescriptions against a CallExpr
119  /// @{
120
121  /// Returns true if the CallExpr is a call to a function that matches the
122  /// CallDescription.
123  ///
124  /// When available, always prefer matching with a CallEvent! This function
125  /// exists only when that is not available, for example, when _only_
126  /// syntactic check is done on a piece of code.
127  ///
128  /// Also, StdLibraryFunctionsChecker::Signature is likely a better candicade
129  /// for syntactic only matching if you are writing a new checker. This is
130  /// handy if a CallDescriptionMap is already there.
131  ///
132  /// The function is imprecise because CallEvent may know path sensitive
133  /// information, such as the precise argument count (see comments for
134  /// CallEvent::getNumArgs), the called function if it was called through a
135  /// function pointer, and other information not available syntactically.
136  bool matchesAsWritten(const CallExpr &CE) const;
137
138  /// Returns true whether the CallExpr matches on any of the CallDescriptions
139  /// supplied.
140  ///
141  /// \note This function is not intended to be used to match Obj-C method
142  /// calls.
143  friend bool matchesAnyAsWritten(const CallExpr &CE,
144                                  const CallDescription &CD1) {
145    return CD1.matchesAsWritten(CE);
146  }
147
148  /// \copydoc clang::ento::CallDescription::matchesAnyAsWritten(const CallExpr &, const CallDescription &)
149  template <typename... Ts>
150  friend bool matchesAnyAsWritten(const CallExpr &CE,
151                                  const CallDescription &CD1,
152                                  const Ts &...CDs) {
153    return CD1.matchesAsWritten(CE) || matchesAnyAsWritten(CE, CDs...);
154  }
155  /// @}
156
157private:
158  bool matchesImpl(const FunctionDecl *Callee, size_t ArgCount,
159                   size_t ParamCount) const;
160};
161
162/// An immutable map from CallDescriptions to arbitrary data. Provides a unified
163/// way for checkers to react on function calls.
164template <typename T> class CallDescriptionMap {
165  friend class CallDescriptionSet;
166
167  // Some call descriptions aren't easily hashable (eg., the ones with qualified
168  // names in which some sections are omitted), so let's put them
169  // in a simple vector and use linear lookup.
170  // TODO: Implement an actual map for fast lookup for "hashable" call
171  // descriptions (eg., the ones for C functions that just match the name).
172  std::vector<std::pair<CallDescription, T>> LinearMap;
173
174public:
175  CallDescriptionMap(
176      std::initializer_list<std::pair<CallDescription, T>> &&List)
177      : LinearMap(List) {}
178
179  template <typename InputIt>
180  CallDescriptionMap(InputIt First, InputIt Last) : LinearMap(First, Last) {}
181
182  ~CallDescriptionMap() = default;
183
184  // These maps are usually stored once per checker, so let's make sure
185  // we don't do redundant copies.
186  CallDescriptionMap(const CallDescriptionMap &) = delete;
187  CallDescriptionMap &operator=(const CallDescription &) = delete;
188
189  CallDescriptionMap(CallDescriptionMap &&) = default;
190  CallDescriptionMap &operator=(CallDescriptionMap &&) = default;
191
192  [[nodiscard]] const T *lookup(const CallEvent &Call) const {
193    // Slow path: linear lookup.
194    // TODO: Implement some sort of fast path.
195    for (const std::pair<CallDescription, T> &I : LinearMap)
196      if (I.first.matches(Call))
197        return &I.second;
198
199    return nullptr;
200  }
201
202  /// When available, always prefer lookup with a CallEvent! This function
203  /// exists only when that is not available, for example, when _only_
204  /// syntactic check is done on a piece of code.
205  ///
206  /// Also, StdLibraryFunctionsChecker::Signature is likely a better candicade
207  /// for syntactic only matching if you are writing a new checker. This is
208  /// handy if a CallDescriptionMap is already there.
209  ///
210  /// The function is imprecise because CallEvent may know path sensitive
211  /// information, such as the precise argument count (see comments for
212  /// CallEvent::getNumArgs), the called function if it was called through a
213  /// function pointer, and other information not available syntactically.
214  [[nodiscard]] const T *lookupAsWritten(const CallExpr &Call) const {
215    // Slow path: linear lookup.
216    // TODO: Implement some sort of fast path.
217    for (const std::pair<CallDescription, T> &I : LinearMap)
218      if (I.first.matchesAsWritten(Call))
219        return &I.second;
220
221    return nullptr;
222  }
223};
224
225/// An immutable set of CallDescriptions.
226/// Checkers can efficiently decide if a given CallEvent matches any
227/// CallDescription in the set.
228class CallDescriptionSet {
229  CallDescriptionMap<bool /*unused*/> Impl = {};
230
231public:
232  CallDescriptionSet(std::initializer_list<CallDescription> &&List);
233
234  CallDescriptionSet(const CallDescriptionSet &) = delete;
235  CallDescriptionSet &operator=(const CallDescription &) = delete;
236
237  [[nodiscard]] bool contains(const CallEvent &Call) const;
238
239  /// When available, always prefer lookup with a CallEvent! This function
240  /// exists only when that is not available, for example, when _only_
241  /// syntactic check is done on a piece of code.
242  ///
243  /// Also, StdLibraryFunctionsChecker::Signature is likely a better candicade
244  /// for syntactic only matching if you are writing a new checker. This is
245  /// handy if a CallDescriptionMap is already there.
246  ///
247  /// The function is imprecise because CallEvent may know path sensitive
248  /// information, such as the precise argument count (see comments for
249  /// CallEvent::getNumArgs), the called function if it was called through a
250  /// function pointer, and other information not available syntactically.
251  [[nodiscard]] bool containsAsWritten(const CallExpr &CE) const;
252};
253
254} // namespace ento
255} // namespace clang
256
257#endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CALLDESCRIPTION_H
258