clang-tools  8.0.0
ProperlySeededRandomGeneratorCheck.cpp
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1 //===--- ProperlySeededRandomGeneratorCheck.cpp - clang-tidy---------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "llvm/ADT/STLExtras.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace cert {
20 
21 ProperlySeededRandomGeneratorCheck::ProperlySeededRandomGeneratorCheck(
22  StringRef Name, ClangTidyContext *Context)
23  : ClangTidyCheck(Name, Context),
24  RawDisallowedSeedTypes(
25  Options.get("DisallowedSeedTypes", "time_t,std::time_t")) {
26  StringRef(RawDisallowedSeedTypes).split(DisallowedSeedTypes, ',');
27 }
28 
31  Options.store(Opts, "DisallowedSeedTypes", RawDisallowedSeedTypes);
32 }
33 
35  auto RandomGeneratorEngineDecl = cxxRecordDecl(hasAnyName(
36  "::std::linear_congruential_engine", "::std::mersenne_twister_engine",
37  "::std::subtract_with_carry_engine", "::std::discard_block_engine",
38  "::std::independent_bits_engine", "::std::shuffle_order_engine"));
39  auto RandomGeneratorEngineTypeMatcher = hasType(hasUnqualifiedDesugaredType(
40  recordType(hasDeclaration(RandomGeneratorEngineDecl))));
41 
42  // std::mt19937 engine;
43  // engine.seed();
44  // ^
45  // engine.seed(1);
46  // ^
47  // const int x = 1;
48  // engine.seed(x);
49  // ^
50  Finder->addMatcher(
51  cxxMemberCallExpr(
52  has(memberExpr(has(declRefExpr(RandomGeneratorEngineTypeMatcher)),
53  member(hasName("seed")),
54  unless(hasDescendant(cxxThisExpr())))))
55  .bind("seed"),
56  this);
57 
58  // std::mt19937 engine;
59  // ^
60  // std::mt19937 engine(1);
61  // ^
62  // const int x = 1;
63  // std::mt19937 engine(x);
64  // ^
65  Finder->addMatcher(
66  cxxConstructExpr(RandomGeneratorEngineTypeMatcher).bind("ctor"), this);
67 
68  // srand();
69  // ^
70  // const int x = 1;
71  // srand(x);
72  // ^
73  Finder->addMatcher(
74  callExpr(callee(functionDecl(hasAnyName("::srand", "::std::srand"))))
75  .bind("srand"),
76  this);
77 }
78 
80  const MatchFinder::MatchResult &Result) {
81  const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructExpr>("ctor");
82  if (Ctor)
83  checkSeed(Result, Ctor);
84 
85  const auto *Func = Result.Nodes.getNodeAs<CXXMemberCallExpr>("seed");
86  if (Func)
87  checkSeed(Result, Func);
88 
89  const auto *Srand = Result.Nodes.getNodeAs<CallExpr>("srand");
90  if (Srand)
91  checkSeed(Result, Srand);
92 }
93 
94 template <class T>
95 void ProperlySeededRandomGeneratorCheck::checkSeed(
96  const MatchFinder::MatchResult &Result, const T *Func) {
97  if (Func->getNumArgs() == 0 || Func->getArg(0)->isDefaultArgument()) {
98  diag(Func->getExprLoc(),
99  "random number generator seeded with a default argument will generate "
100  "a predictable sequence of values");
101  return;
102  }
103 
104  Expr::EvalResult EVResult;
105  if (Func->getArg(0)->EvaluateAsInt(EVResult, *Result.Context)) {
106  diag(Func->getExprLoc(),
107  "random number generator seeded with a constant value will generate a "
108  "predictable sequence of values");
109  return;
110  }
111 
112  const std::string SeedType(
113  Func->getArg(0)->IgnoreCasts()->getType().getAsString());
114  if (llvm::find(DisallowedSeedTypes, SeedType) != DisallowedSeedTypes.end()) {
115  diag(Func->getExprLoc(),
116  "random number generator seeded with a disallowed source of seed "
117  "value will generate a predictable sequence of values");
118  return;
119  }
120 }
121 
122 } // namespace cert
123 } // namespace tidy
124 } // namespace clang
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.
Definition: ClangTidy.cpp:473
void registerMatchers(ast_matchers::MatchFinder *Finder) override
Override this to register AST matchers with Finder.
Base class for all clang-tidy checks.
Definition: ClangTidy.h:127
void storeOptions(ClangTidyOptions::OptionMap &Opts) override
Should store all options supported by this check with their current values or default values for opti...
static constexpr llvm::StringLiteral Name
std::map< std::string, std::string > OptionMap
llvm::Optional< llvm::Expected< tooling::AtomicChanges > > Result
===– Representation.cpp - ClangDoc Representation --------—*- C++ -*-===//
Every ClangTidyCheck reports errors through a DiagnosticsEngine provided by this context.
void check(const ast_matchers::MatchFinder::MatchResult &Result) override
ClangTidyChecks that register ASTMatchers should do the actual work in here.
DiagnosticBuilder diag(SourceLocation Loc, StringRef Description, DiagnosticIDs::Level Level=DiagnosticIDs::Warning)
Add a diagnostic with the check&#39;s name.
Definition: ClangTidy.cpp:438