C++ has the following builtin types:

These fundamental types are always available, without having to include a header file. These types are exactly the same in either C++ or in C.

Specializing parts of the library on these types is prohibited: instead, use a POD.

The header limits defines traits classes to give access to various implementation defined-aspects of the fundamental types. The traits classes -- fourteen in total -- are all specializations of the class template numeric_limits and defined as follows:

   template<typename T>
     struct class
     {
       static const bool is_specialized;
       static T max() throw();
       static T min() throw();

       static const int digits;
       static const int digits10;
       static const bool is_signed;
       static const bool is_integer;
       static const bool is_exact;
       static const int radix;
       static T epsilon() throw();
       static T round_error() throw();

       static const int min_exponent;
       static const int min_exponent10;
       static const int max_exponent;
       static const int max_exponent10;

       static const bool has_infinity;
       static const bool has_quiet_NaN;
       static const bool has_signaling_NaN;
       static const float_denorm_style has_denorm;
       static const bool has_denorm_loss;
       static T infinity() throw();
       static T quiet_NaN() throw();
       static T denorm_min() throw();

       static const bool is_iec559;
       static const bool is_bounded;
       static const bool is_modulo;

       static const bool traps;
       static const bool tinyness_before;
       static const float_round_style round_style;
     };
   

The only change that might affect people is the type of NULL: while it is required to be a macro, the definition of that macro is not allowed to be (void*)0, which is often used in C.

For g++, NULL is #define'd to be __null, a magic keyword extension of g++.

The biggest problem of #defining NULL to be something like “0L” is that the compiler will view that as a long integer before it views it as a pointer, so overloading won't do what you expect. (This is why g++ has a magic extension, so that NULL is always a pointer.)

In his book Effective C++, Scott Meyers points out that the best way to solve this problem is to not overload on pointer-vs-integer types to begin with. He also offers a way to make your own magic NULL that will match pointers before it matches integers.

See the Effective C++ CD example.