1 files changed, 119 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/bugprone/RandomGeneratorSeedCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/RandomGeneratorSeedCheck.cpp
new file mode 100644
index 0000000..3e32e9b
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/RandomGeneratorSeedCheck.cpp
@@ -0,0 +1,119 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "RandomGeneratorSeedCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "llvm/ADT/STLExtras.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+RandomGeneratorSeedCheck::RandomGeneratorSeedCheck(StringRef Name,
+                                                   ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      RawDisallowedSeedTypes(
+          Options.get("DisallowedSeedTypes", "time_t,std::time_t")) {
+  RawDisallowedSeedTypes.split(DisallowedSeedTypes, ',');
+}
+
+void RandomGeneratorSeedCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "DisallowedSeedTypes", RawDisallowedSeedTypes);
+}
+
+void RandomGeneratorSeedCheck::registerMatchers(MatchFinder *Finder) {
+  auto RandomGeneratorEngineDecl = cxxRecordDecl(hasAnyName(
+      "::std::linear_congruential_engine", "::std::mersenne_twister_engine",
+      "::std::subtract_with_carry_engine", "::std::discard_block_engine",
+      "::std::independent_bits_engine", "::std::shuffle_order_engine"));
+  auto RandomGeneratorEngineTypeMatcher = hasType(hasUnqualifiedDesugaredType(
+      recordType(hasDeclaration(RandomGeneratorEngineDecl))));
+
+  // std::mt19937 engine;
+  // engine.seed();
+  //        ^
+  // engine.seed(1);
+  //        ^
+  // const int x = 1;
+  // engine.seed(x);
+  //        ^
+  Finder->addMatcher(
+      cxxMemberCallExpr(
+          has(memberExpr(has(declRefExpr(RandomGeneratorEngineTypeMatcher)),
+                         member(hasName("seed")),
+                         unless(hasDescendant(cxxThisExpr())))))
+          .bind("seed"),
+      this);
+
+  // std::mt19937 engine;
+  //              ^
+  // std::mt19937 engine(1);
+  //              ^
+  // const int x = 1;
+  // std::mt19937 engine(x);
+  //              ^
+  Finder->addMatcher(
+      traverse(TK_AsIs,
+               cxxConstructExpr(RandomGeneratorEngineTypeMatcher).bind("ctor")),
+      this);
+
+  // srand();
+  // ^
+  // const int x = 1;
+  // srand(x);
+  // ^
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(hasAnyName("::srand", "::std::srand"))))
+          .bind("srand"),
+      this);
+}
+
+void RandomGeneratorSeedCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructExpr>("ctor");
+  if (Ctor)
+    checkSeed(Result, Ctor);
+
+  const auto *Func = Result.Nodes.getNodeAs<CXXMemberCallExpr>("seed");
+  if (Func)
+    checkSeed(Result, Func);
+
+  const auto *Srand = Result.Nodes.getNodeAs<CallExpr>("srand");
+  if (Srand)
+    checkSeed(Result, Srand);
+}
+
+template <class T>
+void RandomGeneratorSeedCheck::checkSeed(const MatchFinder::MatchResult &Result,
+                                         const T *Func) {
+  if (Func->getNumArgs() == 0 || Func->getArg(0)->isDefaultArgument()) {
+    diag(Func->getExprLoc(),
+         "random number generator seeded with a default argument will generate "
+         "a predictable sequence of values");
+    return;
+  }
+
+  Expr::EvalResult EVResult;
+  if (Func->getArg(0)->EvaluateAsInt(EVResult, *Result.Context)) {
+    diag(Func->getExprLoc(),
+         "random number generator seeded with a constant value will generate a "
+         "predictable sequence of values");
+    return;
+  }
+
+  const std::string SeedType(
+      Func->getArg(0)->IgnoreCasts()->getType().getAsString());
+  if (llvm::is_contained(DisallowedSeedTypes, SeedType)) {
+    diag(Func->getExprLoc(),
+         "random number generator seeded with a disallowed source of seed "
+         "value will generate a predictable sequence of values");
+    return;
+  }
+}
+
+} // namespace clang::tidy::bugprone