musl/include/bits/wexitstatus.h

#ifndef WEXITSTATUS
#define WEXITSTATUS(s) (((s) & 0xff00) >> 8)
#define WTERMSIG(s) ((s) & 0x7f)
#define WSTOPSIG(s) WEXITSTATUS(s)
#define WCOREDUMP(s) ((s) & 0x80)
#define WIFEXITED(s) (!WTERMSIG(s))
#define WIFSTOPPED(s) (((s) & 0xff) == 0x7f)
#define WIFSIGNALED(s) (!WIFSTOPPED(s) && !WIFEXITED(s))
#endif