Defines the macros traditionally defined in the Standard C library header <signal.h>.
#if <TRADITIONAL C HEADERS>
   #include <signal.h>
namespace std {
   using ::sig_atomic_t;
   using ::raise;
   using ::signal;
}
#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.