Don't bother to set sockaddr_un.sun_len.

It's not necessary to fill in sun_len when calling bind() or connect(),
on all known systems that have it.

Discussion: https://postgr.es/m/2781112.1644819528%40sss.pgh.pa.us

src/common/ip.c

@@ -218,20 +218,6 @@ getaddrinfo_unix(const char *path, const struct addrinfo *hintsp,
 		aip->ai_addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(path);
 	}
 
-	/*
-	 * The standard recommendation for filling sun_len is to set it to the
-	 * struct size (independently of the actual path length).  However, that
-	 * draws an integer-overflow warning on AIX 7.1, where sun_len is just
-	 * uint8 yet the struct size exceeds 255 bytes.  It's likely that nothing
-	 * is paying attention to sun_len on that platform, but we have to do
-	 * something with it.  To suppress the warning, clamp the struct size to
-	 * what will fit in sun_len.
-	 */
-#ifdef HAVE_STRUCT_SOCKADDR_SA_LEN
-	unp->sun_len = Min(sizeof(struct sockaddr_un),
-					   ((size_t) 1 << (sizeof(unp->sun_len) * BITS_PER_BYTE)) - 1);
-#endif
-
 	return 0;
 }