# Extra Clang Tools 21.1.8 documentation

## clang-tidy - cert-msc51-cpp

# cert-msc51-cpp

This check flags all pseudo-random number engines, engine adaptor instantiations and `srand()` when initialized or seeded with default argument, constant expression or any user-configurable type. Pseudo-random number engines seeded with a predictable value may cause vulnerabilities e.g. in security protocols. This is a CERT security rule, see MSC51-CPP. Ensure your random number generator is properly seeded and MSC32-C. Properly seed pseudorandom number generators.

Examples:

    void foo() {
      std::mt19937 engine1; // Diagnose, always generate the same sequence
      std::mt19937 engine2(1); // Diagnose
      engine1.seed(); // Diagnose
      engine2.seed(1); // Diagnose

      std::time_t t;
      engine1.seed(std::time(&t)); // Diagnose, system time might be controlled by user

      int x = atoi(argv[1]);
      std::mt19937 engine3(x);  // Will not warn
    }

## Options

DisallowedSeedTypes

  A comma-separated list of the type names which are disallowed. Default value is time_t,std::time_t.