diff --git a/usr.sbin/envstat/envstat.c b/usr.sbin/envstat/envstat.c
index 8310bfc41c4d..fda49ab66802 100644
--- a/usr.sbin/envstat/envstat.c
+++ b/usr.sbin/envstat/envstat.c
@@ -1,4 +1,4 @@
-/* $NetBSD: envstat.c,v 1.100 2020/11/14 16:32:53 mlelstv Exp $ */
+/* $NetBSD: envstat.c,v 1.101 2021/11/27 22:30:25 rillig Exp $ */
 
 /*-
  * Copyright (c) 2007, 2008 Juan Romero Pardines.
@@ -27,7 +27,7 @@
 
 #include <sys/cdefs.h>
 #ifndef lint
-__RCSID("$NetBSD: envstat.c,v 1.100 2020/11/14 16:32:53 mlelstv Exp $");
+__RCSID("$NetBSD: envstat.c,v 1.101 2021/11/27 22:30:25 rillig Exp $");
 #endif /* not lint */
 
 #include <stdio.h>
@@ -986,7 +986,7 @@ do {								\
 		ilen = 9;					\
 	} else							\
 		ilen += 9;					\
-} while (/* CONSTCOND */ 0)
+} while (0)
 
 		/* temperatures */
 		} else if (strcmp(sensor->type, "Temperature") == 0) {
diff --git a/usr.sbin/makemandb/apropos-utils.c b/usr.sbin/makemandb/apropos-utils.c
index a1d94930d954..066c90d36f37 100644
--- a/usr.sbin/makemandb/apropos-utils.c
+++ b/usr.sbin/makemandb/apropos-utils.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: apropos-utils.c,v 1.47 2019/08/18 09:14:30 abhinav Exp $	*/
+/*	$NetBSD: apropos-utils.c,v 1.48 2021/11/27 22:30:25 rillig Exp $	*/
 /*-
  * Copyright (c) 2011 Abhinav Upadhyay <er.abhinav.upadhyay@gmail.com>
  * All rights reserved.
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: apropos-utils.c,v 1.47 2019/08/18 09:14:30 abhinav Exp $");
+__RCSID("$NetBSD: apropos-utils.c,v 1.48 2021/11/27 22:30:25 rillig Exp $");
 
 #include <sys/queue.h>
 #include <sys/stat.h>
@@ -784,7 +784,7 @@ get_escaped_html_string(const char *src, size_t *slen)
     do {					\
 	memcpy(dst, (a), sizeof(a) - 1);	\
 	dst += sizeof(a) - 1; 			\
-    } while (/*CONSTCOND*/0)
+    } while (0)
 
 
 	ddst = dst = emalloc(*slen + count * 5 + 1);
diff --git a/usr.sbin/ndp/ndp.c b/usr.sbin/ndp/ndp.c
index 1f54aa6dac3e..902b95520000 100644
--- a/usr.sbin/ndp/ndp.c
+++ b/usr.sbin/ndp/ndp.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: ndp.c,v 1.58 2020/09/15 10:11:35 roy Exp $	*/
+/*	$NetBSD: ndp.c,v 1.59 2021/11/27 22:30:25 rillig Exp $	*/
 /*	$KAME: ndp.c,v 1.121 2005/07/13 11:30:13 keiichi Exp $	*/
 
 /*
@@ -812,7 +812,7 @@ ifinfo(char *ifname, int argc, char **argv)
 				newflags |= (f);\
 			flagset = true; \
 		}\
-	} while (/*CONSTCOND*/0)
+	} while (0)
 /*
  * XXX: this macro is not 100% correct, in that it matches "nud" against
  *      "nudbogus".  But we just let it go since this is minor.
@@ -833,7 +833,7 @@ ifinfo(char *ifname, int argc, char **argv)
 			v = newval; \
 			valset = true; \
 		} \
-	} while (/*CONSTCOND*/0)
+	} while (0)
 
 #ifdef ND6_IFF_IFDISABLED
 		SETFLAG("disabled", ND6_IFF_IFDISABLED);
diff --git a/usr.sbin/nfsd/nfsd.c b/usr.sbin/nfsd/nfsd.c
index 94fc3b44a171..df2dcd403047 100644
--- a/usr.sbin/nfsd/nfsd.c
+++ b/usr.sbin/nfsd/nfsd.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: nfsd.c,v 1.73 2020/09/17 12:48:12 christos Exp $	*/
+/*	$NetBSD: nfsd.c,v 1.74 2021/11/27 22:30:25 rillig Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993, 1994
@@ -42,7 +42,7 @@ __COPYRIGHT("@(#) Copyright (c) 1989, 1993, 1994\
 #if 0
 static char sccsid[] = "@(#)nfsd.c	8.9 (Berkeley) 3/29/95";
 #else
-__RCSID("$NetBSD: nfsd.c,v 1.73 2020/09/17 12:48:12 christos Exp $");
+__RCSID("$NetBSD: nfsd.c,v 1.74 2021/11/27 22:30:25 rillig Exp $");
 #endif
 #endif /* not lint */
 
@@ -114,7 +114,7 @@ do {									\
 	} else {							\
 		syslog(e, s, ## args);					\
 	}								\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 static void	nonfs(int);
 __dead static void	usage(void);
diff --git a/usr.sbin/pstat/pstat.c b/usr.sbin/pstat/pstat.c
index 11a41d370d5f..bd78dd05bf55 100644
--- a/usr.sbin/pstat/pstat.c
+++ b/usr.sbin/pstat/pstat.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: pstat.c,v 1.132 2021/04/12 05:11:09 mrg Exp $	*/
+/*	$NetBSD: pstat.c,v 1.133 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*-
  * Copyright (c) 1980, 1991, 1993, 1994
@@ -39,7 +39,7 @@ __COPYRIGHT("@(#) Copyright (c) 1980, 1991, 1993, 1994\
 #if 0
 static char sccsid[] = "@(#)pstat.c	8.16 (Berkeley) 5/9/95";
 #else
-__RCSID("$NetBSD: pstat.c,v 1.132 2021/04/12 05:11:09 mrg Exp $");
+__RCSID("$NetBSD: pstat.c,v 1.133 2021/11/27 22:30:26 rillig Exp $");
 #endif
 #endif /* not lint */
 
@@ -135,13 +135,13 @@ struct flagbit_desc {
 #define	KGET2(addr, p, s, msg) do {					\
 	if (kvm_read(kd, (u_long)(addr), p, s) != s)			\
 		warnx("cannot read %s: %s", msg, kvm_geterr(kd));	\
-} while (/* CONSTCOND */0)
+} while (0)
 #define	KGETRET(addr, p, s, msg) do {					\
 	if (kvm_read(kd, (u_long)(addr), p, s) != s) {			\
 		warnx("cannot read %s: %s", msg, kvm_geterr(kd));	\
 		return (0);						\
 	}								\
-} while (/* CONSTCOND */0)
+} while (0)
 
 #if 1				/* This is copied from vmstat/vmstat.c */
 /*
@@ -158,7 +158,7 @@ struct flagbit_desc {
 	    (val)) - (width);				\
 	if ((ovflw) < 0)				\
 		(ovflw) = 0;				\
-} while (/* CONSTCOND */0)
+} while (0)
 #endif
 
 void	filemode(void);
diff --git a/usr.sbin/pwd_mkdb/pwd_mkdb.c b/usr.sbin/pwd_mkdb/pwd_mkdb.c
index 37f0be88378a..a1c3f6011983 100644
--- a/usr.sbin/pwd_mkdb/pwd_mkdb.c
+++ b/usr.sbin/pwd_mkdb/pwd_mkdb.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: pwd_mkdb.c,v 1.58 2017/05/04 16:26:09 sevan Exp $	*/
+/*	$NetBSD: pwd_mkdb.c,v 1.59 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*
  * Copyright (c) 2000, 2009 The NetBSD Foundation, Inc.
@@ -90,7 +90,7 @@ __COPYRIGHT("@(#) Copyright (c) 2000, 2009\
  The NetBSD Foundation, Inc.  All rights reserved.\
   Copyright (c) 1991, 1993, 1994\
  The Regents of the University of California.  All rights reserved.");
-__RCSID("$NetBSD: pwd_mkdb.c,v 1.58 2017/05/04 16:26:09 sevan Exp $");
+__RCSID("$NetBSD: pwd_mkdb.c,v 1.59 2021/11/27 22:30:26 rillig Exp $");
 #endif /* not lint */
 
 #if HAVE_NBTOOL_CONFIG_H
@@ -850,7 +850,7 @@ putdbents(struct pwddb *db, struct passwd *pw, const char *passwd, int flags,
 			(void)memmove(p, &pwvar, sizeof(pwvar)); \
 			p += sizeof(pwvar); \
 		} \
-	} while (/*CONSTCOND*/0)
+	} while (0)
 
 	/* Create insecure data. */
 	p = buf;
@@ -1007,7 +1007,7 @@ getdbent(struct pwddb *db, int type, void *keyp, struct passwd **tpwd)
 			if (lorder != BYTE_ORDER) \
 				pwvar = SWAP(pwvar); \
 		} \
-	} while (/*CONSTCOND*/0)
+	} while (0)
 		
 	READPWTIMEVAR(pwd.pw_change);
 
diff --git a/usr.sbin/rtadvd/config.c b/usr.sbin/rtadvd/config.c
index bce28f611e2f..933709699fac 100644
--- a/usr.sbin/rtadvd/config.c
+++ b/usr.sbin/rtadvd/config.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: config.c,v 1.46 2021/03/23 18:16:53 christos Exp $	*/
+/*	$NetBSD: config.c,v 1.47 2021/11/27 22:30:26 rillig Exp $	*/
 /*	$KAME: config.c,v 1.93 2005/10/17 14:40:02 suz Exp $	*/
 
 /*
@@ -178,13 +178,13 @@ getconfig(const char *intface, int exithard)
 		goto errexit;						\
 	}								\
 	var = t;							\
-     } while (/*CONSTCOND*/0)
+     } while (0)
 
 #define MAYHAVE(var, cap, def)						\
      do {								\
 	if ((var = agetnum(cap)) < 0)					\
 		var = def;						\
-     } while (/*CONSTCOND*/0)
+     } while (0)
 
 #define	ELM_MALLOC(p)							\
 	do {								\
@@ -1072,7 +1072,7 @@ make_packet(struct rainfo *rainfo)
 			    __func__, __LINE__, packlen); \
 			exit(EXIT_FAILURE); \
 		} \
-	} while (/*CONSTCOND*/0)
+	} while (0)
 	/*
 	 * construct the packet
 	 */
diff --git a/usr.sbin/syslogd/sign.c b/usr.sbin/syslogd/sign.c
index 89129895daee..4d9da320bb90 100644
--- a/usr.sbin/syslogd/sign.c
+++ b/usr.sbin/syslogd/sign.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: sign.c,v 1.7 2018/02/06 21:36:46 christos Exp $	*/
+/*	$NetBSD: sign.c,v 1.8 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -66,7 +66,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: sign.c,v 1.7 2018/02/06 21:36:46 christos Exp $");
+__RCSID("$NetBSD: sign.c,v 1.8 2021/11/27 22:30:26 rillig Exp $");
 
 #ifndef DISABLE_SIGN
 #include "syslogd.h"
@@ -313,14 +313,14 @@ sign_sg_init(struct filed *Files)
 		logerror("Unable to allocate memory");	\
 		return false;				\
 	}						\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 #define ALLOC_SG(x) do {				\
 	ALLOC_OR_FALSE(x);				\
 	(x)->last_msg_num = 1; /* cf. section 4.2.5 */	\
 	STAILQ_INIT(&(x)->hashes);			\
 	STAILQ_INIT(&(x)->files);			\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 /* alloc(fq) and add to SGs file queue */
 #define ASSIGN_FQ() do {				\
@@ -329,7 +329,7 @@ sign_sg_init(struct filed *Files)
 	f->f_sg = newsg;				\
 	DPRINTF(D_SIGN, "SG@%p <--> f@%p\n", newsg, f); \
 	STAILQ_INSERT_TAIL(&newsg->files, fq, entries); \
-} while (/*CONSTCOND*/0)
+} while (0)
 
 	switch (GlobalSign.sg) {
 	case 0:
diff --git a/usr.sbin/syslogd/sign.h b/usr.sbin/syslogd/sign.h
index af786825302c..99903809af36 100644
--- a/usr.sbin/syslogd/sign.h
+++ b/usr.sbin/syslogd/sign.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: sign.h,v 1.2 2008/11/07 07:36:38 minskim Exp $	*/
+/*	$NetBSD: sign.h,v 1.3 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -126,7 +126,7 @@
 		    ERR_error_string(ERR_get_error(), NULL));	     	\
 		return 1;					     	\
 	}								\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 /* structs use uint_fast64_t in different places because the standard
  * requires values in interval [0:9999999999 = SIGN_MAX_COUNT] */
diff --git a/usr.sbin/syslogd/syslogd.c b/usr.sbin/syslogd/syslogd.c
index 2cbb2efbf021..c909983db2f4 100644
--- a/usr.sbin/syslogd/syslogd.c
+++ b/usr.sbin/syslogd/syslogd.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: syslogd.c,v 1.137 2021/08/13 20:19:14 andvar Exp $	*/
+/*	$NetBSD: syslogd.c,v 1.138 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*
  * Copyright (c) 1983, 1988, 1993, 1994
@@ -39,7 +39,7 @@ __COPYRIGHT("@(#) Copyright (c) 1983, 1988, 1993, 1994\
 #if 0
 static char sccsid[] = "@(#)syslogd.c	8.3 (Berkeley) 4/4/94";
 #else
-__RCSID("$NetBSD: syslogd.c,v 1.137 2021/08/13 20:19:14 andvar Exp $");
+__RCSID("$NetBSD: syslogd.c,v 1.138 2021/11/27 22:30:26 rillig Exp $");
 #endif
 #endif /* not lint */
 
@@ -3518,7 +3518,7 @@ init(int fd, short event, void *ev)
 	}							\
 	src->f_qsize = 0;					\
 	src->f_qelements = 0;					\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 	/*
 	 *  Free old log files.
diff --git a/usr.sbin/syslogd/syslogd.h b/usr.sbin/syslogd/syslogd.h
index 378ac6a398f1..781944588f80 100644
--- a/usr.sbin/syslogd/syslogd.h
+++ b/usr.sbin/syslogd/syslogd.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: syslogd.h,v 1.8 2019/02/11 19:45:54 mrg Exp $	*/
+/*	$NetBSD: syslogd.h,v 1.9 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -163,7 +163,7 @@ void dbprintf(const char *, const char *, size_t, const char *, ...)
 	if (event_add(x, NULL) == -1) {					\
 		DPRINTF(D_EVENT, "Failure in event_add()\n");		\
 	}								\
-} while (/*CONSTCOND*/0)
+} while (0)
 #define RETRYEVENT_ADD(x) do {						\
 	struct timeval _tv;						\
 	_tv.tv_sec = 0;							\
@@ -172,13 +172,13 @@ void dbprintf(const char *, const char *, size_t, const char *, ...)
 	if (event_add(x, &_tv) == -1) {					\
 		DPRINTF(D_EVENT, "Failure in event_add()\n");		\
 	}								\
-} while (/*CONSTCOND*/0)
+} while (0)
 #define DEL_EVENT(x) do {						\
 	DPRINTF(D_MEM2, "DEL_EVENT(%s@%p)\n", #x, x);			\
 	if ((x) && (event_del(x) == -1)) {				\
 		DPRINTF(D_EVENT, "Failure in event_del()\n");		\
 	}								\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 /* safe calls to free() */
 #define FREEPTR(x)	if (x) {					\
@@ -213,7 +213,7 @@ void dbprintf(const char *, const char *, size_t, const char *, ...)
 		message_allqueues_purge();				\
 	}								\
 	DPRINTF(D_MEM2, "MALLOC(%s@%p, %zu)\n", #ptr, ptr, size);	\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 #define CALLOC(ptr, size) do {						\
 	while(!(ptr = calloc(1, size))) {				\
@@ -221,7 +221,7 @@ void dbprintf(const char *, const char *, size_t, const char *, ...)
 		message_allqueues_purge();				\
 	}								\
 	DPRINTF(D_MEM2, "CALLOC(%s@%p, %zu)\n", #ptr, ptr, size);	\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 /* define strlen(NULL) to be 0 */
 #define SAFEstrlen(x) ((x) ? strlen(x) : 0)
@@ -232,7 +232,7 @@ void dbprintf(const char *, const char *, size_t, const char *, ...)
 	sigaddset(&newmask, SIGHUP);					\
 	sigaddset(&newmask, SIGALRM);					\
 	sigprocmask(SIG_BLOCK, &newmask, &omask);			\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 #define RESTORE_SIGNALS(omask) sigprocmask(SIG_SETMASK, &omask, NULL)
 
@@ -240,7 +240,7 @@ void dbprintf(const char *, const char *, size_t, const char *, ...)
 #define SEND_QUEUE(f) do {						\
 	if ((f)->f_qelements)						\
 		send_queue(0, 0, f);	      				\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 #define MAXUNAMES		20	/* maximum number of user names */
 #define BSD_TIMESTAMPLEN	(14+1)
diff --git a/usr.sbin/syslogd/tls.c b/usr.sbin/syslogd/tls.c
index 0ca880af4827..825bf2acdad8 100644
--- a/usr.sbin/syslogd/tls.c
+++ b/usr.sbin/syslogd/tls.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: tls.c,v 1.18 2021/09/16 22:19:12 andvar Exp $	*/
+/*	$NetBSD: tls.c,v 1.19 2021/11/27 22:30:26 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -45,7 +45,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: tls.c,v 1.18 2021/09/16 22:19:12 andvar Exp $");
+__RCSID("$NetBSD: tls.c,v 1.19 2021/11/27 22:30:26 rillig Exp $");
 
 #ifndef DISABLE_TLS
 #include <sys/stat.h>
@@ -123,7 +123,7 @@ out:
 		    TLS_CONN_STATES[x], TLS_CONN_STATES[y]);	\
 		(x) = (y);					\
 	}							\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 static unsigned
 getVerifySetting(const char *x509verifystring)