Remove support for using wait3() in place of waitpid().

All Unix-oid platforms that we currently support should have waitpid(),
since it's in V2 of the Single Unix Spec.  Our git history shows that
the wait3 code was added to support NextStep, which we officially dropped
support for as of 9.2.  So get rid of the configure test, and simplify the
macro spaghetti in reaper().  Per suggestion from Fujii Masao.

configure

@@ -19254,8 +19254,7 @@ fi
 
 
 
-
-for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit memmove poll pstat readlink setproctitle setsid sigprocmask symlink towlower utime utimes waitpid wcstombs wcstombs_l
+for ac_func in cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit memmove poll pstat readlink setproctitle setsid sigprocmask symlink towlower utime utimes wcstombs wcstombs_l
 do
 as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 { $as_echo "$as_me:$LINENO: checking for $ac_func" >&5

configure.in

@@ -1207,7 +1207,7 @@ PGAC_VAR_INT_TIMEZONE
 AC_FUNC_ACCEPT_ARGTYPES
 PGAC_FUNC_GETTIMEOFDAY_1ARG
 
-AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit memmove poll pstat readlink setproctitle setsid sigprocmask symlink towlower utime utimes waitpid wcstombs wcstombs_l])
+AC_CHECK_FUNCS([cbrt dlopen fdatasync getifaddrs getpeerucred getrlimit memmove poll pstat readlink setproctitle setsid sigprocmask symlink towlower utime utimes wcstombs wcstombs_l])
 
 AC_REPLACE_FUNCS(fseeko)
 case $host_os in

src/backend/postmaster/postmaster.c

@@ -377,7 +377,9 @@ static void InitPostmasterDeathWatchHandle(void);
 #ifdef EXEC_BACKEND
 
 #ifdef WIN32
-static pid_t win32_waitpid(int *exitstatus);
+#define WNOHANG 0				/* ignored, so any integer value will do */
+
+static pid_t waitpid(pid_t pid, int *exitstatus, int options);
 static void WINAPI pgwin32_deadchild_callback(PVOID lpParameter, BOOLEAN TimerOrWaitFired);
 
 static HANDLE win32ChildQueue;
@@ -388,7 +390,7 @@ typedef struct
 	HANDLE		procHandle;
 	DWORD		procId;
 } win32_deadchild_waitinfo;
-#endif
+#endif /* WIN32 */
 
 static pid_t backend_forkexec(Port *port);
 static pid_t internal_forkexec(int argc, char *argv[], Port *port);
@@ -2268,33 +2270,13 @@ reaper(SIGNAL_ARGS)
 	int			pid;			/* process id of dead child process */
 	int			exitstatus;		/* its exit status */
 
-	/* These macros hide platform variations in getting child status */
-#ifdef HAVE_WAITPID
-	int			status;			/* child exit status */
-
-#define LOOPTEST()		((pid = waitpid(-1, &status, WNOHANG)) > 0)
-#define LOOPHEADER()	(exitstatus = status)
-#else							/* !HAVE_WAITPID */
-#ifndef WIN32
-	union wait	status;			/* child exit status */
-
-#define LOOPTEST()		((pid = wait3(&status, WNOHANG, NULL)) > 0)
-#define LOOPHEADER()	(exitstatus = status.w_status)
-#else							/* WIN32 */
-#define LOOPTEST()		((pid = win32_waitpid(&exitstatus)) > 0)
-#define LOOPHEADER()
-#endif   /* WIN32 */
-#endif   /* HAVE_WAITPID */
-
 	PG_SETMASK(&BlockSig);
 
 	ereport(DEBUG4,
 			(errmsg_internal("reaping dead processes")));
 
-	while (LOOPTEST())
+	while ((pid = waitpid(-1, &exitstatus, WNOHANG)) > 0)
 	{
-		LOOPHEADER();
-
 		/*
 		 * Check if this child was a startup process.
 		 */
@@ -5045,8 +5027,12 @@ ShmemBackendArrayRemove(Backend *bn)
 
 #ifdef WIN32
 
+/*
+ * Subset implementation of waitpid() for Windows.  We assume pid is -1
+ * (that is, check all child processes) and options is WNOHANG (don't wait).
+ */
 static pid_t
-win32_waitpid(int *exitstatus)
+waitpid(pid_t pid, int *exitstatus, int options)
 {
 	DWORD		dwd;
 	ULONG_PTR	key;

src/include/pg_config.h.in

@@ -614,9 +614,6 @@
 /* Define to 1 if you have the `vsnprintf' function. */
 #undef HAVE_VSNPRINTF
 
-/* Define to 1 if you have the `waitpid' function. */
-#undef HAVE_WAITPID
-
 /* Define to 1 if you have the <wchar.h> header file. */
 #undef HAVE_WCHAR_H
 

src/include/pg_config.h.win32

@@ -505,9 +505,6 @@
 /* Define to 1 if you have the `vsnprintf' function. */
 #define HAVE_VSNPRINTF 1
 
-/* Define to 1 if you have the `waitpid' function. */
-/* #undef HAVE_WAITPID */
-
 /* Define to 1 if you have the <wchar.h> header file. */
 #define HAVE_WCHAR_H 1