feat(wait): wait/waitpid/waitid and status macros

src/process/wait.c

@@ -0,0 +1,59 @@
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <sys/wait.h>
+
+#include "../internal/syscall.h"
+
+/*
+ * wait/waitpid/waitid/wait3/wait4 — child-process status collection.
+ *
+ * All four are pass-throughs to the kernel: wait/waitpid/wait3/wait4 ride
+ * SYS_wait4 (the kernel does the pid selection, the option masking, and the
+ * status-word encoding), waitid rides SYS_waitid (which fills a full
+ * 128-byte siginfo with the si_pid/si_uid/si_status details and a CLD_*
+ * si_code). The raw result goes through syscall_ret(), so a child pid (or
+ * waitid's 0) is returned on success and -1 with errno set on error;
+ * WNOHANG-with-no-child returns 0 from the kernel untouched.
+ *
+ * No argument inspection is needed: the kernel interprets pid == -1 (any
+ * child), 0 (own process group) and pid < -1 (process group) for wait4, and
+ * the which/id pair for waitid, exactly as POSIX specifies. The options are
+ * the kernel-identical W* bits from <sys/wait.h>. rusage passes through
+ * verbatim for wait3/wait4 (NULL is legal and skips the fill).
+ */
+
+pid_t
+wait(int *stat_loc)
+{
+    return (pid_t)syscall_ret(__syscall4(SYS_wait4, -1, (long)stat_loc, 0, 0));
+}
+
+pid_t
+waitpid(pid_t pid, int *stat_loc, int options)
+{
+    return (pid_t)syscall_ret(__syscall4(SYS_wait4, pid, (long)stat_loc, options, 0));
+}
+
+int
+waitid(idtype_t idtype, id_t id, siginfo_t *infop, int options)
+{
+    return syscall_ret(__syscall5(SYS_waitid, idtype, id, (long)infop, options, 0));
+}
+
+#if VLIBC_LEVEL_GE(2)
+/* Level 2 (muslmimic): XSI wait3/wait4. */
+
+pid_t
+wait3(int *stat_loc, int options, struct rusage *rusage)
+{
+    return (pid_t)syscall_ret(__syscall4(SYS_wait4, -1, (long)stat_loc, options, (long)rusage));
+}
+
+pid_t
+wait4(pid_t pid, int *stat_loc, int options, struct rusage *rusage)
+{
+    return (pid_t)syscall_ret(__syscall4(SYS_wait4, pid, (long)stat_loc, options, (long)rusage));
+}
+#endif /* VLIBC_LEVEL_GE(2) */