1 //===- CalledOnceCheck.h - Check 'called once' parameters -------*- 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 //  This file defines a check for function-like parameters that should be
10 //  called exactly one time.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_ANALYSIS_ANALYSES_CALLEDONCECHECK_H
15 #define LLVM_CLANG_ANALYSIS_ANALYSES_CALLEDONCECHECK_H
16 
17 namespace clang {
18 
19 class AnalysisDeclContext;
20 class CFG;
21 class Decl;
22 class DeclContext;
23 class Expr;
24 class ParmVarDecl;
25 class Stmt;
26 
27 /// Classification of situations when parameter is not called on every path.
28 /// \enum IfThen -- then branch of the if statement has no call.
29 /// \enum IfElse -- else branch of the if statement has no call.
30 /// \enum Switch -- one of the switch cases doesn't have a call.
31 /// \enum SwitchSkipped -- there is no call if none of the cases appies.
32 /// \enum LoopEntered -- no call when the loop is entered.
33 /// \enum LoopSkipped -- no call when the loop is not entered.
34 /// \enum FallbackReason -- fallback case when we were not able to figure out
35 /// the reason.
36 enum class NeverCalledReason {
37   IfThen,
38   IfElse,
39   Switch,
40   SwitchSkipped,
41   LoopEntered,
42   LoopSkipped,
43   FallbackReason,
44   LARGEST_VALUE = FallbackReason
45 };
46 
47 class CalledOnceCheckHandler {
48 public:
49   CalledOnceCheckHandler() = default;
50   virtual ~CalledOnceCheckHandler() = default;
51 
52   /// Called when parameter is called twice.
53   /// \param Parameter -- parameter that should be called once.
54   /// \param Call -- call to report the warning.
55   /// \param PrevCall -- previous call.
56   /// \param IsCompletionHandler -- true, if parameter is a completion handler.
57   /// \param Poised -- true, if the second call is guaranteed to happen after
58   /// the first call.
59   virtual void handleDoubleCall(const ParmVarDecl *Parameter, const Expr *Call,
60                                 const Expr *PrevCall, bool IsCompletionHandler,
61                                 bool Poised) {}
62 
63   /// Called when parameter is not called at all.
64   /// \param Parameter -- parameter that should be called once.
65   /// \param IsCompletionHandler -- true, if parameter is a completion handler.
66   virtual void handleNeverCalled(const ParmVarDecl *Parameter,
67                                  bool IsCompletionHandler) {}
68 
69   /// Called when captured parameter is not called at all.
70   /// \param Parameter -- parameter that should be called once.
71   /// \param Where -- declaration that captures \p Parameter
72   /// \param IsCompletionHandler -- true, if parameter is a completion handler.
73   virtual void handleCapturedNeverCalled(const ParmVarDecl *Parameter,
74                                          const Decl *Where,
75                                          bool IsCompletionHandler) {}
76 
77   /// Called when parameter is not called on one of the paths.
78   /// Usually we try to find a statement that is the least common ancestor of
79   /// the path containing the call and not containing the call.  This helps us
80   /// to pinpoint a bad path for the user.
81   /// \param Parameter -- parameter that should be called once.
82   /// \param Where -- the least common ancestor statement.
83   /// \param Reason -- a reason describing the path without a call.
84   /// \param IsCalledDirectly -- true, if parameter actually gets called on
85   /// the other path.  It is opposed to be used in some other way (added to some
86   /// collection, passed as a parameter, etc.).
87   /// \param IsCompletionHandler -- true, if parameter is a completion handler.
88   virtual void handleNeverCalled(const ParmVarDecl *Parameter,
89                                  const Stmt *Where, NeverCalledReason Reason,
90                                  bool IsCalledDirectly,
91                                  bool IsCompletionHandler) {}
92 };
93 
94 /// Check given CFG for 'called once' parameter violations.
95 ///
96 /// It traverses the function and tracks how such parameters are used.
97 /// It detects two main violations:
98 ///   * parameter is called twice
99 ///   * parameter is not called
100 ///
101 /// \param AC -- context.
102 /// \param Handler -- a handler for found violations.
103 /// \param CheckConventionalParameters -- true, if we want to check parameters
104 /// not explicitly marked as 'called once', but having the same requirements
105 /// according to conventions.
106 void checkCalledOnceParameters(AnalysisDeclContext &AC,
107                                CalledOnceCheckHandler &Handler,
108                                bool CheckConventionalParameters);
109 
110 } // end namespace clang
111 
112 #endif /* LLVM_CLANG_ANALYSIS_ANALYSES_CALLEDONCECHECK_H */
113