standards/55429: SA_RESTART not available if -D_POSIX_C_SOURCE=200809L

[coypu%sdf.org@localhost]

>Number:         55429
>Category:       standards
>Synopsis:       SA_RESTART not available if -D_POSIX_C_SOURCE=200809L
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    standards-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 28 12:05:00 +0000 2020
>Originator:     coypu
>Release:        NetBSD 9.99.63
>Organization:
>Environment:
NetBSD planets 9.99.63 NetBSD 9.99.63 (GENERIC) #4: Sun May 24 22:55:24 IDT 2020  fly@planets:/home/fly/obj/sys/arch/amd64/compile/GENERIC amd64

>Description:
#define _POSIX_C_SOURCE 200809L
#include <signal.h>
int main() {
	return SA_RESTART;
}

~> cc test.c
test.c: In function ?main?:
test.c:4:9: error: ?SA_RESTART? undeclared (first use in this function)
  return SA_RESTART;
         ^~~~~~~~~~
test.c:4:9: note: each undeclared identifier is reported only once for each function it appears in

>How-To-Repeat:

>Fix:
I can't understand POSIX.