Defines the macros traditionally defined in the Standard C library header <stddef.h>.
#if <TRADITIONAL C HEADERS>
#include <stddef.h>
namespace std {
using ::ptrdiff_t;
using ::size_t;
}
#endif
Remarks
Including this header also ensures that the names declared with external linkage in the Standard C library header are declared in the std namespace. In this implementation, the names may or may not also be declared in the global namespace, depending on the specific translation environment.