For a namespace clean function, implement _wait, otherwise implement wait. The implementation of this functionality will be tightly bound to any operating infrastructure for handling multiple processes.

A minimal implementation has only one process, so can wait for no other process and should always fail with an appropriate value in errno.

#include <errno.h>

#undef errno
extern int  errno;

int
_wait (int *status)
{
  errno = ECHILD;
  return -1;                    /* Always fails */

}       /* _wait () */