cert-dcl58-cpp

Modification of the std or posix namespace can result in undefined behavior. This check warns for such modifications. The std (or posix) namespace is allowed to be extended with (class or function) template specializations that depend on an user-defined type (a type that is not defined in the standard system headers).

The check detects the following (user provided) declarations in namespace std or posix:

• Anything that is not a template specialization.

• Explicit specializations of any standard library function template or class template, if it does not have any user-defined type as template argument.

• Explicit specializations of any member function of a standard library class template.

• Explicit specializations of any member function template of a standard library class or class template.

• Explicit or partial specialization of any member class template of a standard library class or class template.

Examples:

namespace std {
  int x; // warning: modification of 'std' namespace can result in undefined behavior [cert-dcl58-cpp]
}

namespace posix::a { // warning: modification of 'posix' namespace can result in undefined behavior
}

template <>
struct ::std::hash<long> { // warning: modification of 'std' namespace can result in undefined behavior
  unsigned long operator()(const long &K) const {
    return K;
  }
};

struct MyData { long data; };

template <>
struct ::std::hash<MyData> { // no warning: specialization with user-defined type
  unsigned long operator()(const MyData &K) const {
    return K.data;
  }
};

namespace std {
  template <>
  void swap<bool>(bool &a, bool &b); // warning: modification of 'std' namespace can result in undefined behavior

  template <>
  bool less<void>::operator()<MyData &&, MyData &&>(MyData &&, MyData &&) const { // warning: modification of 'std' namespace can result in undefined behavior
    return true;
  }
}

This check corresponds to the CERT C++ Coding Standard rule DCL58-CPP. Do not modify the standard namespaces.