diff --git a/usr.bin/col/col.c b/usr.bin/col/col.c
index b329e2440cdd..d11b650598d4 100644
--- a/usr.bin/col/col.c
+++ b/usr.bin/col/col.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: col.c,v 1.19 2020/11/01 22:27:15 christos Exp $	*/
+/*	$NetBSD: col.c,v 1.20 2021/09/10 21:52:17 rillig Exp $	*/
 
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
@@ -47,7 +47,7 @@ __FBSDID("$FreeBSD: head/usr.bin/col/col.c 366577 2020-10-09 15:27:37Z markj $")
 ;
 
 #endif
-__RCSID("$NetBSD: col.c,v 1.19 2020/11/01 22:27:15 christos Exp $");
+__RCSID("$NetBSD: col.c,v 1.20 2021/09/10 21:52:17 rillig Exp $");
 #endif /* not lint */
 
 #include <err.h>
@@ -123,7 +123,7 @@ static int	pass_unknown_seqs;	/* pass unknown control sequences */
 	do {					\
 		if (putwchar(ch) == WEOF)	\
 			errx(EXIT_FAILURE, "write error");	\
-	} while (/*CONSTCOND*/0)
+	} while (0)
 
 int
 main(int argc, char **argv)
diff --git a/usr.bin/config/scan.l b/usr.bin/config/scan.l
index b45c457ef915..994224cc205b 100644
--- a/usr.bin/config/scan.l
+++ b/usr.bin/config/scan.l
@@ -1,5 +1,5 @@
 %{
-/*	$NetBSD: scan.l,v 1.33 2020/07/26 22:25:47 uwe Exp $	*/
+/*	$NetBSD: scan.l,v 1.34 2021/09/10 21:52:17 rillig Exp $	*/
 
 /*
  * Copyright (c) 1992, 1993
@@ -42,7 +42,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: scan.l,v 1.33 2020/07/26 22:25:47 uwe Exp $");
+__RCSID("$NetBSD: scan.l,v 1.34 2021/09/10 21:52:17 rillig Exp $");
 
 #include <sys/param.h>
 #include <errno.h>
@@ -90,7 +90,7 @@ int	 ifdefshift = -1;
 		printf("%s%s [%d,%d,%d] %#" PRIx64 "\n", x, # s, \
 		    IDS_PARENT_DISABLED, IDS_ISMATCH(st), getcurifdef(), \
 		    ifdefstate); \
-	} while (/*CONSTCOND*/0)
+	} while (0)
 #else
 # define IDS_PRINT(s, st, x) ((void)0)
 #endif
diff --git a/usr.bin/ftp/ftp_var.h b/usr.bin/ftp/ftp_var.h
index 4d4224ff8a2a..3f03581afc87 100644
--- a/usr.bin/ftp/ftp_var.h
+++ b/usr.bin/ftp/ftp_var.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: ftp_var.h,v 1.85 2017/11/20 21:11:36 kre Exp $	*/
+/*	$NetBSD: ftp_var.h,v 1.86 2021/09/10 21:52:17 rillig Exp $	*/
 
 /*-
  * Copyright (c) 1996-2009 The NetBSD Foundation, Inc.
@@ -341,7 +341,7 @@ extern	struct option	optiontab[];
 #define DPRINTF(...)	(void)0
 #define DWARN(...)	(void)0
 #else
-#define DWFTP(a)	do a; while (/*CONSTCOND*/0)
+#define DWFTP(a)	do a; while (0)
 #define DPRINTF(...)	DWFTP(if (ftp_debug) (void)fprintf(ttyout, __VA_ARGS__))
 #define DWARN(...)	DWFTP(if (ftp_debug) warn(__VA_ARGS__))
 #endif
diff --git a/usr.bin/gzip/unlz.c b/usr.bin/gzip/unlz.c
index 2cefac3d22f4..e3d5623b59d8 100644
--- a/usr.bin/gzip/unlz.c
+++ b/usr.bin/gzip/unlz.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: unlz.c,v 1.6 2018/11/11 01:42:36 christos Exp $	*/
+/*	$NetBSD: unlz.c,v 1.7 2021/09/10 21:52:17 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -393,7 +393,7 @@ lz_bm_init(int *a, size_t l)
 	size_t l = __arraycount(a[0]); \
 	for (size_t i = 0; i < __arraycount(a); i++) \
 		lz_bm_init(a[i], l); \
-} while (/*CONSTCOND*/0)
+} while (0)
 
 #define LZ_MODEL_INIT(a) do { \
 	a.choice1 = BIT_MODEL_INIT; \
@@ -401,7 +401,7 @@ lz_bm_init(int *a, size_t l)
 	LZ_BM_INIT2(a.bm_low); \
 	LZ_BM_INIT2(a.bm_mid); \
 	LZ_BM_INIT(a.bm_high); \
-} while (/*CONSTCOND*/0)
+} while (0)
 		
 static bool
 lz_decode_member(struct lz_decoder *lz)
diff --git a/usr.bin/login/login_pam.c b/usr.bin/login/login_pam.c
index 7d877ebeb1c0..e05856895577 100644
--- a/usr.bin/login/login_pam.c
+++ b/usr.bin/login/login_pam.c
@@ -1,4 +1,4 @@
-/*     $NetBSD: login_pam.c,v 1.26 2020/02/08 13:44:35 kamil Exp $       */
+/*     $NetBSD: login_pam.c,v 1.27 2021/09/10 21:52:17 rillig Exp $       */
 
 /*-
  * Copyright (c) 1980, 1987, 1988, 1991, 1993, 1994
@@ -39,7 +39,7 @@ __COPYRIGHT("@(#) Copyright (c) 1980, 1987, 1988, 1991, 1993, 1994\
 #if 0
 static char sccsid[] = "@(#)login.c	8.4 (Berkeley) 4/2/94";
 #endif
-__RCSID("$NetBSD: login_pam.c,v 1.26 2020/02/08 13:44:35 kamil Exp $");
+__RCSID("$NetBSD: login_pam.c,v 1.27 2021/09/10 21:52:17 rillig Exp $");
 #endif /* not lint */
 
 /*
@@ -258,7 +258,7 @@ main(int argc, char *argv[])
 	warnx("%s: %s", msg, pam_strerror(pamh, pam_err));		\
 	pam_end(pamh, pam_err);						\
 	sleepexit(EXIT_FAILURE);					\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 		pam_err = pam_start("login", username, &pamc, &pamh);
 		if (pam_err != PAM_SUCCESS) {
@@ -274,7 +274,7 @@ main(int argc, char *argv[])
 	pam_err = pam_set_item(pamh, (item), (var));			\
 	if (pam_err != PAM_SUCCESS)					\
 		PAM_END("pam_set_item(" # item ")");			\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 		/* 
 		 * Fill hostname tty, and nested user
diff --git a/usr.bin/mail/thread.c b/usr.bin/mail/thread.c
index 7e0c63d463a5..e4ae729a6046 100644
--- a/usr.bin/mail/thread.c
+++ b/usr.bin/mail/thread.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: thread.c,v 1.10 2012/10/21 22:18:16 christos Exp $	*/
+/*	$NetBSD: thread.c,v 1.11 2021/09/10 21:52:18 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2006 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
 
 #include <sys/cdefs.h>
 #ifndef __lint__
-__RCSID("$NetBSD: thread.c,v 1.10 2012/10/21 22:18:16 christos Exp $");
+__RCSID("$NetBSD: thread.c,v 1.11 2021/09/10 21:52:18 rillig Exp $");
 #endif /* not __lint__ */
 
 #include <assert.h>
@@ -453,7 +453,7 @@ thread_fix_old_links(struct message *nmessage, struct message *message, int omsg
 # define FIX_LINK(p)	do {\
 	if (p)\
 		p = nmessage + (p - message);\
-  } while (/*CONSTCOND*/0)
+  } while (0)
 
 	FIX_LINK(current_thread.t_head);
 	for (i = 0; i < omsgCount; i++) {
diff --git a/usr.bin/netstat/inet6.c b/usr.bin/netstat/inet6.c
index d81743bd1d8e..b518d8386ec4 100644
--- a/usr.bin/netstat/inet6.c
+++ b/usr.bin/netstat/inet6.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: inet6.c,v 1.77 2020/08/28 07:23:48 ozaki-r Exp $	*/
+/*	$NetBSD: inet6.c,v 1.78 2021/09/10 21:52:18 rillig Exp $	*/
 /*	BSDI inet.c,v 2.3 1995/10/24 02:19:29 prb Exp	*/
 
 /*
@@ -64,7 +64,7 @@
 #if 0
 static char sccsid[] = "@(#)inet.c	8.4 (Berkeley) 4/20/94";
 #else
-__RCSID("$NetBSD: inet6.c,v 1.77 2020/08/28 07:23:48 ozaki-r Exp $");
+__RCSID("$NetBSD: inet6.c,v 1.78 2021/09/10 21:52:18 rillig Exp $");
 #endif
 #endif /* not lint */
 
@@ -747,7 +747,7 @@ ip6_stats(u_long off, const char *name)
 			printf("\t\t%llu addresses scope=%x\n",\
 			       (unsigned long long)ip6stat[s], i);\
 		}\
-	} while(/*CONSTCOND*/0);
+	} while(0);
 
 	p(IP6_STAT_SOURCES_NONE,
 	  "\t%llu failure%s of source address selection\n");
diff --git a/usr.bin/passwd/pam_passwd.c b/usr.bin/passwd/pam_passwd.c
index 57cba406ddc3..ff240a994e3e 100644
--- a/usr.bin/passwd/pam_passwd.c
+++ b/usr.bin/passwd/pam_passwd.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: pam_passwd.c,v 1.6 2010/03/09 16:14:08 joerg Exp $	*/
+/*	$NetBSD: pam_passwd.c,v 1.7 2021/09/10 21:52:18 rillig Exp $	*/
 
 /*-
  * Copyright (c) 2002 Networks Associates Technologies, Inc.
@@ -38,7 +38,7 @@
 #ifdef __FreeBSD__
 __FBSDID("$FreeBSD: src/usr.bin/passwd/passwd.c,v 1.23 2003/04/18 21:27:09 nectar Exp $");
 #else
-__RCSID("$NetBSD: pam_passwd.c,v 1.6 2010/03/09 16:14:08 joerg Exp $");
+__RCSID("$NetBSD: pam_passwd.c,v 1.7 2021/09/10 21:52:18 rillig Exp $");
 #endif
 
 #include <sys/param.h>
@@ -67,7 +67,7 @@ do {									\
 		warnx("%s: %s", (msg), pam_strerror(pamh, pam_err));	\
 		goto end;						\
 	}								\
-} while (/*CONSTCOND*/0)
+} while (0)
 
 void
 pwpam_process(const char *username, int argc, char **argv)
diff --git a/usr.bin/su/su_pam.c b/usr.bin/su/su_pam.c
index da69e67cdccc..8e6bfeb886fe 100644
--- a/usr.bin/su/su_pam.c
+++ b/usr.bin/su/su_pam.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: su_pam.c,v 1.21 2018/02/26 00:05:05 htodd Exp $	*/
+/*	$NetBSD: su_pam.c,v 1.22 2021/09/10 21:52:18 rillig Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -39,7 +39,7 @@ __COPYRIGHT("@(#) Copyright (c) 1988\
 #if 0
 static char sccsid[] = "@(#)su.c	8.3 (Berkeley) 4/2/94";*/
 #else
-__RCSID("$NetBSD: su_pam.c,v 1.21 2018/02/26 00:05:05 htodd Exp $");
+__RCSID("$NetBSD: su_pam.c,v 1.22 2021/09/10 21:52:18 rillig Exp $");
 #endif
 #endif /* not lint */
 
@@ -220,7 +220,7 @@ main(int argc, char **argv)
 	/*
 	 * PAM initialization
 	 */
-#define PAM_END(msg) do { func = msg; goto done;} /* NOTREACHED */ while (/*CONSTCOND*/0)
+#define PAM_END(msg) do { func = msg; goto done;} /* NOTREACHED */ while (0)
 
 	if ((pam_err = pam_start("su", user, &pamc, &pamh)) != PAM_SUCCESS) {
 		if (pamh != NULL)
diff --git a/usr.bin/tip/tip.h b/usr.bin/tip/tip.h
index 146d5324d0de..038467099343 100644
--- a/usr.bin/tip/tip.h
+++ b/usr.bin/tip/tip.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: tip.h,v 1.34 2020/04/23 00:35:14 joerg Exp $	*/
+/*	$NetBSD: tip.h,v 1.35 2021/09/10 21:52:18 rillig Exp $	*/
 
 /*
  * Copyright (c) 1989, 1993
@@ -155,10 +155,10 @@ typedef
 #define	character(v)	((char)(intptr_t)(v))
 #define	address(v)	((long *)(intptr_t)(v))
 
-#define	setnumber(v,n)		do { (v) = (char *)(intptr_t)(n); } while (/*CONSTCOND*/0)
-#define	setboolean(v,n)		do { (v) = (char *)(intptr_t)(n); } while (/*CONSTCOND*/0)
-#define	setcharacter(v,n)	do { (v) = (char *)(intptr_t)(n); } while (/*CONSTCOND*/0)
-#define	setaddress(v,n)		do { (v) = (char *)(intptr_t)(n); } while (/*CONSTCOND*/0)
+#define	setnumber(v,n)		do { (v) = (char *)(intptr_t)(n); } while (0)
+#define	setboolean(v,n)		do { (v) = (char *)(intptr_t)(n); } while (0)
+#define	setcharacter(v,n)	do { (v) = (char *)(intptr_t)(n); } while (0)
+#define	setaddress(v,n)		do { (v) = (char *)(intptr_t)(n); } while (0)
 
 /*
  * Escape command table definitions --
diff --git a/usr.bin/unzip/unzip.c b/usr.bin/unzip/unzip.c
index d9740139c858..0d8e8f872fad 100644
--- a/usr.bin/unzip/unzip.c
+++ b/usr.bin/unzip/unzip.c
@@ -1,4 +1,4 @@
-/* $NetBSD: unzip.c,v 1.27 2021/02/18 18:06:02 christos Exp $ */
+/* $NetBSD: unzip.c,v 1.28 2021/09/10 21:52:18 rillig Exp $ */
 
 /*-
  * Copyright (c) 2009, 2010 Joerg Sonnenberger <joerg@NetBSD.org>
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: unzip.c,v 1.27 2021/02/18 18:06:02 christos Exp $");
+__RCSID("$NetBSD: unzip.c,v 1.28 2021/09/10 21:52:18 rillig Exp $");
 
 #ifdef __GLIBC__
 #define _GNU_SOURCE
@@ -97,7 +97,7 @@ static int		 tty;
 		int acret = (call);				\
 		if (acret != ARCHIVE_OK)			\
 			errorx("%s", archive_error_string(a));	\
-	} while (/*CONSTCOND*/0)
+	} while (0)
 
 /*
  * Indicates that last info() did not end with EOL.  This helps error() et