Update timezone code from tzcode 2015g.

This patch updates the timezone code from tzcode 2015g.  The Makefile
and README changes are based on those in Paul's patch
<https://sourceware.org/ml/libc-alpha/2015-05/msg00553.html>.

Tested for x86_64 and x86.

2016-01-06  Paul Eggert  <eggert@cs.ucla.edu>
	    Joseph Myers  <joseph@codesourcery.com>

	* timezone/private.h: Update from tzcode 2015g.
	* timezone/tzfile.h: Likewise.
	* timezone/tzselect.ksh: Likewise.
	* timezone/zdump.c: Likewise.
	* timezone/zic.c: Likewise.
	* timezone/ialloc.c: Remove file.
	* timezone/scheck.c: Likewise.
	* timezone/Makefile (extra-objs): Remove variable.
	($(objpfx)zic): Do not depend on scheck.o and ialloc.o.
	(tz-cflags): Add -DHAVE_GETTEXT -DUSE_LTZ=0
	-Wno-maybe-uninitialized.
	(CFLAGS-zdump.c): Remove -fwrapv -DNOID -DHAVE_GETTEXT.
	(CFLAGS-zic.c): Remove -DNOID -DHAVE_GETTEXT.
	(CFLAGS-ialloc.c): Remove variable.
	(CFLAGS-scheck.c): Likewise.
	* timezone/README: Update list of files from tzcode.

1 files changed, 616 insertions, 445 deletions

diff --git a/timezone/zic.c b/timezone/zic.c
index 07d6c30..78ab870 100644
--- a/timezone/zic.c
+++ b/timezone/zic.c
@@ -23,7 +23,7 @@ typedef int_fast64_t	zic_t;
 #endif /* !defined ZIC_MAX_ABBR_LEN_WO_WARN */
 
 #if HAVE_SYS_STAT_H
-#include "sys/stat.h"
+#include <sys/stat.h>
 #endif
 #ifdef S_IRUSR
 #define MKDIR_UMASK (S_IRUSR|S_IWUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH)
@@ -31,21 +31,6 @@ typedef int_fast64_t	zic_t;
 #define MKDIR_UMASK 0755
 #endif
 
-/*
-** On some ancient hosts, predicates like `isspace(C)' are defined
-** only if isascii(C) || C == EOF. Modern hosts obey the C Standard,
-** which says they are defined only if C == ((unsigned char) C) || C == EOF.
-** Neither the C Standard nor Posix require that `isascii' exist.
-** For portability, we check both ancient and modern requirements.
-** If isascii is not defined, the isascii check succeeds trivially.
-*/
-#include "ctype.h"
-#ifndef isascii
-#define isascii(x) 1
-#endif
-
-#define end(cp)	(strchr((cp), '\0'))
-
 struct rule {
 	const char *	r_filename;
 	int		r_linenum;
@@ -54,8 +39,8 @@ struct rule {
 	zic_t		r_loyear;	/* for example, 1986 */
 	zic_t		r_hiyear;	/* for example, 1986 */
 	const char *	r_yrtype;
-	int		r_lowasnum;
-	int		r_hiwasnum;
+	bool		r_lowasnum;
+	bool		r_hiwasnum;
 
 	int		r_month;	/* 0..11 */
 
@@ -64,10 +49,10 @@ struct rule {
 	int		r_wday;
 
 	zic_t		r_tod;		/* time from midnight */
-	int		r_todisstd;	/* above is standard time if TRUE */
-					/* or wall clock time if FALSE */
-	int		r_todisgmt;	/* above is GMT if TRUE */
-					/* or local time if FALSE */
+	bool		r_todisstd;	/* above is standard time if 1 */
+					/* or wall clock time if 0 */
+	bool		r_todisgmt;	/* above is GMT if 1 */
+					/* or local time if 0 */
 	zic_t		r_stdoff;	/* offset from standard time */
 	const char *	r_abbrvar;	/* variable part of abbreviation */
 
@@ -91,6 +76,7 @@ struct zone {
 	zic_t		z_gmtoff;
 	const char *	z_rule;
 	const char *	z_format;
+	char		z_format_specifier;
 
 	zic_t		z_stdoff;
 
@@ -115,25 +101,25 @@ extern int	optind;
 #endif
 
 static void	addtt(zic_t starttime, int type);
-static int	addtype(zic_t gmtoff, const char * abbr, int isdst,
-				int ttisstd, int ttisgmt);
-static void	leapadd(zic_t t, int positive, int rolling, int count);
+static int	addtype(zic_t, char const *, bool, bool, bool);
+static void	leapadd(zic_t, bool, int, int);
 static void	adjleap(void);
 static void	associate(void);
 static void	dolink(const char * fromfield, const char * tofield);
 static char **	getfields(char * buf);
-static zic_t	gethms(const char * string, const char * errstrng,
-		       int signable);
+static zic_t	gethms(const char * string, const char * errstring,
+		       bool);
 static void	infile(const char * filename);
 static void	inleap(char ** fields, int nfields);
 static void	inlink(char ** fields, int nfields);
 static void	inrule(char ** fields, int nfields);
-static int	inzcont(char ** fields, int nfields);
-static int	inzone(char ** fields, int nfields);
-static int	inzsub(char ** fields, int nfields, int iscont);
+static bool	inzcont(char ** fields, int nfields);
+static bool	inzone(char ** fields, int nfields);
+static bool	inzsub(char **, int, bool);
 static int	itsdir(const char * name);
-static int	lowerit(int c);
-static int	mkdirs(char * filename);
+static bool	is_alpha(char a);
+static char	lowerit(char);
+static bool	mkdirs(char *);
 static void	newabbr(const char * abbr);
 static zic_t	oadd(zic_t t1, zic_t t2);
 static void	outzone(const struct zone * zp, int ntzones);
@@ -143,21 +129,25 @@ static void	rulesub(struct rule * rp,
 			const char * typep, const char * monthp,
 			const char * dayp, const char * timep);
 static zic_t	tadd(zic_t t1, zic_t t2);
-static int	yearistype(int year, const char * type);
+static bool	yearistype(int year, const char * type);
+
+/* Bound on length of what %z can expand to.  */
+enum { PERCENT_Z_LEN_BOUND = sizeof "+995959" - 1 };
 
 static int		charcnt;
-static int		errors;
+static bool		errors;
+static bool		warnings;
 static const char *	filename;
 static int		leapcnt;
-static int		leapseen;
+static bool		leapseen;
 static zic_t		leapminyear;
 static zic_t		leapmaxyear;
 static int		linenum;
-static int		max_abbrvar_len;
+static int		max_abbrvar_len = PERCENT_Z_LEN_BOUND;
 static int		max_format_len;
 static zic_t		max_year;
 static zic_t		min_year;
-static int		noise;
+static bool		noise;
 static const char *	rfilename;
 static int		rlinenum;
 static const char *	progname;
@@ -333,8 +323,8 @@ static struct lookup const	end_years[] = {
 };
 
 static struct lookup const	leap_types[] = {
-	{ "Rolling",	TRUE },
-	{ "Stationary",	FALSE },
+	{ "Rolling",	true },
+	{ "Stationary",	false },
 	{ NULL,		0 }
 };
 
@@ -354,8 +344,8 @@ static struct attype {
 static zic_t		gmtoffs[TZ_MAX_TYPES];
 static char		isdsts[TZ_MAX_TYPES];
 static unsigned char	abbrinds[TZ_MAX_TYPES];
-static char		ttisstds[TZ_MAX_TYPES];
-static char		ttisgmts[TZ_MAX_TYPES];
+static bool		ttisstds[TZ_MAX_TYPES];
+static bool		ttisgmts[TZ_MAX_TYPES];
 static char		chars[TZ_MAX_CHARS];
 static zic_t		trans[TZ_MAX_LEAPS];
 static zic_t		corr[TZ_MAX_LEAPS];
@@ -376,22 +366,44 @@ static ATTRIBUTE_PURE size_t
 size_product(size_t nitems, size_t itemsize)
 {
 	if (SIZE_MAX / itemsize < nitems)
-		memory_exhausted("size overflow");
+		memory_exhausted(_("size overflow"));
 	return nitems * itemsize;
 }
 
+#if !HAVE_STRDUP
+static char *
+strdup(char const *str)
+{
+  char *result = malloc(strlen(str) + 1);
+  return result ? strcpy(result, str) : result;
+}
+#endif
+
 static ATTRIBUTE_PURE void *
-memcheck(void *const ptr)
+memcheck(void *ptr)
 {
 	if (ptr == NULL)
 		memory_exhausted(strerror(errno));
 	return ptr;
 }
 
-#define emalloc(size)		memcheck(malloc(size))
-#define erealloc(ptr, size)	memcheck(realloc(ptr, size))
-#define ecpyalloc(ptr)		memcheck(icpyalloc(ptr))
-#define ecatalloc(oldp, newp)	memcheck(icatalloc((oldp), (newp)))
+static void *
+emalloc(size_t size)
+{
+  return memcheck(malloc(size));
+}
+
+static void *
+erealloc(void *ptr, size_t size)
+{
+  return memcheck(realloc(ptr, size));
+}
+
+static char *
+ecpyalloc (char const *str)
+{
+  return memcheck(strdup(str));
+}
 
 static void *
 growalloc(void *ptr, size_t itemsize, int nitems, int *nitems_alloc)
@@ -401,7 +413,7 @@ growalloc(void *ptr, size_t itemsize, int nitems, int *nitems_alloc)
 	else {
 		int amax = INT_MAX < SIZE_MAX ? INT_MAX : SIZE_MAX;
 		if ((amax - 1) / 3 * 2 < *nitems_alloc)
-			memory_exhausted("int overflow");
+			memory_exhausted(_("int overflow"));
 		*nitems_alloc = *nitems_alloc + (*nitems_alloc >> 1) + 1;
 		return erealloc(ptr, size_product(*nitems_alloc, itemsize));
 	}
@@ -435,13 +447,13 @@ verror(const char *const string, va_list args)
 	**	zic ... 2>&1 | error -t "*" -v
 	** on BSD systems.
 	*/
-	fprintf(stderr, _("\"%s\", line %d: "), filename, linenum);
+	if (filename)
+	  fprintf(stderr, _("\"%s\", line %d: "), filename, linenum);
 	vfprintf(stderr, string, args);
 	if (rfilename != NULL)
-		(void) fprintf(stderr, _(" (rule from \"%s\", line %d)"),
+		fprintf(stderr, _(" (rule from \"%s\", line %d)"),
 			rfilename, rlinenum);
-	(void) fprintf(stderr, "\n");
-	++errors;
+	fprintf(stderr, "\n");
 }
 
 static void ATTRIBUTE_FORMAT((printf, 1, 2))
@@ -451,6 +463,7 @@ error(const char *const string, ...)
 	va_start(args, string);
 	verror(string, args);
 	va_end(args);
+	errors = true;
 }
 
 static void ATTRIBUTE_FORMAT((printf, 1, 2))
@@ -461,19 +474,35 @@ warning(const char *const string, ...)
 	va_start(args, string);
 	verror(string, args);
 	va_end(args);
-	--errors;
+	warnings = true;
+}
+
+static void
+close_file(FILE *stream, char const *name)
+{
+  char const *e = (ferror(stream) ? _("I/O error")
+		   : fclose(stream) != 0 ? strerror(errno) : NULL);
+  if (e) {
+    fprintf(stderr, "%s: ", progname);
+    if (name)
+      fprintf(stderr, "%s: ", name);
+    fprintf(stderr, "%s\n", e);
+    exit(EXIT_FAILURE);
+  }
 }
 
 static _Noreturn void
 usage(FILE *stream, int status)
 {
-	(void) fprintf(stream, _("%s: usage is %s \
-[ --version ] [ --help ] [ -v ] [ -l localtime ] [ -p posixrules ] \\\n\
-\t[ -d directory ] [ -L leapseconds ] [ -y yearistype ] [ filename ... ]\n\
-\n\
-Report bugs to %s.\n"),
-		       progname, progname, REPORT_BUGS_TO);
-	exit(status);
+  fprintf(stream,
+	  _("%s: usage is %s [ --version ] [ --help ] [ -v ] \\\n"
+	    "\t[ -l localtime ] [ -p posixrules ] [ -d directory ] \\\n"
+	    "\t[ -L leapseconds ] [ filename ... ]\n\n"
+	    "Report bugs to %s.\n"),
+	  progname, progname, REPORT_BUGS_TO);
+  if (status == EXIT_SUCCESS)
+    close_file(stream, NULL);
+  exit(status);
 }
 
 static const char *	psxrules;
@@ -490,25 +519,26 @@ main(int argc, char **argv)
 	register int	c;
 
 #ifdef S_IWGRP
-	(void) umask(umask(S_IWGRP | S_IWOTH) | (S_IWGRP | S_IWOTH));
+	umask(umask(S_IWGRP | S_IWOTH) | (S_IWGRP | S_IWOTH));
 #endif
 #if HAVE_GETTEXT
-	(void) setlocale(LC_ALL, "");
+	setlocale(LC_ALL, "");
 #ifdef TZ_DOMAINDIR
-	(void) bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
+	bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
 #endif /* defined TEXTDOMAINDIR */
-	(void) textdomain(TZ_DOMAIN);
+	textdomain(TZ_DOMAIN);
 #endif /* HAVE_GETTEXT */
 	progname = argv[0];
 	if (TYPE_BIT(zic_t) < 64) {
-		(void) fprintf(stderr, "%s: %s\n", progname,
+		fprintf(stderr, "%s: %s\n", progname,
 			_("wild compilation-time specification of zic_t"));
-		exit(EXIT_FAILURE);
+		return EXIT_FAILURE;
 	}
 	for (i = 1; i < argc; ++i)
 		if (strcmp(argv[i], "--version") == 0) {
-			(void) printf("zic %s%s\n", PKGVERSION, TZVERSION);
-			exit(EXIT_SUCCESS);
+			printf("zic %s%s\n", PKGVERSION, TZVERSION);
+			close_file(stdout, NULL);
+			return EXIT_SUCCESS;
 		} else if (strcmp(argv[i], "--help") == 0) {
 			usage(stdout, EXIT_SUCCESS);
 		}
@@ -520,57 +550,57 @@ main(int argc, char **argv)
 				if (directory == NULL)
 					directory = optarg;
 				else {
-					(void) fprintf(stderr,
+					fprintf(stderr,
 _("%s: More than one -d option specified\n"),
 						progname);
-					exit(EXIT_FAILURE);
+					return EXIT_FAILURE;
 				}
 				break;
 			case 'l':
 				if (lcltime == NULL)
 					lcltime = optarg;
 				else {
-					(void) fprintf(stderr,
+					fprintf(stderr,
 _("%s: More than one -l option specified\n"),
 						progname);
-					exit(EXIT_FAILURE);
+					return EXIT_FAILURE;
 				}
 				break;
 			case 'p':
 				if (psxrules == NULL)
 					psxrules = optarg;
 				else {
-					(void) fprintf(stderr,
+					fprintf(stderr,
 _("%s: More than one -p option specified\n"),
 						progname);
-					exit(EXIT_FAILURE);
+					return EXIT_FAILURE;
 				}
 				break;
 			case 'y':
 				if (yitcommand == NULL)
 					yitcommand = optarg;
 				else {
-					(void) fprintf(stderr,
+					fprintf(stderr,
 _("%s: More than one -y option specified\n"),
 						progname);
-					exit(EXIT_FAILURE);
+					return EXIT_FAILURE;
 				}
 				break;
 			case 'L':
 				if (leapsec == NULL)
 					leapsec = optarg;
 				else {
-					(void) fprintf(stderr,
+					fprintf(stderr,
 _("%s: More than one -L option specified\n"),
 						progname);
-					exit(EXIT_FAILURE);
+					return EXIT_FAILURE;
 				}
 				break;
 			case 'v':
-				noise = TRUE;
+				noise = true;
 				break;
 			case 's':
-				(void) printf("%s: -s ignored\n", progname);
+				warning(_("-s ignored"));
 				break;
 		}
 	if (optind == argc - 1 && strcmp(argv[optind], "=") == 0)
@@ -588,7 +618,7 @@ _("%s: More than one -L option specified\n"),
 	for (i = optind; i < argc; ++i)
 		infile(argv[i]);
 	if (errors)
-		exit(EXIT_FAILURE);
+		return EXIT_FAILURE;
 	associate();
 	for (i = 0; i < nzones; i = j) {
 		/*
@@ -611,53 +641,137 @@ _("%s: More than one -L option specified\n"),
 						warning(_("link to link"));
 	}
 	if (lcltime != NULL) {
-		eat("command line", 1);
+		eat(_("command line"), 1);
 		dolink(lcltime, TZDEFAULT);
 	}
 	if (psxrules != NULL) {
-		eat("command line", 1);
+		eat(_("command line"), 1);
 		dolink(psxrules, TZDEFRULES);
 	}
-	return (errors == 0) ? EXIT_SUCCESS : EXIT_FAILURE;
+	if (warnings && (ferror(stderr) || fclose(stderr) != 0))
+	  return EXIT_FAILURE;
+	return errors ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+
+static bool
+componentcheck(char const *name, char const *component,
+	       char const *component_end)
+{
+	enum { component_len_max = 14 };
+	size_t component_len = component_end - component;
+	if (component_len == 0) {
+	  if (!*name)
+	    error (_("empty file name"));
+	  else
+	    error (_(component == name
+		     ? "file name '%s' begins with '/'"
+		     : *component_end
+		     ? "file name '%s' contains '//'"
+		     : "file name '%s' ends with '/'"),
+		   name);
+	  return false;
+	}
+	if (0 < component_len && component_len <= 2
+	    && component[0] == '.' && component_end[-1] == '.') {
+	  error(_("file name '%s' contains '%.*s' component"),
+		name, (int) component_len, component);
+	  return false;
+	}
+	if (noise) {
+	  if (0 < component_len && component[0] == '-')
+	    warning(_("file name '%s' component contains leading '-'"),
+		    name);
+	  if (component_len_max < component_len)
+	    warning(_("file name '%s' contains overlength component"
+		      " '%.*s...'"),
+		    name, component_len_max, component);
+	}
+	return true;
+}
+
+static bool
+namecheck(const char *name)
+{
+	register char const *cp;
+
+	/* Benign characters in a portable file name.  */
+	static char const benign[] =
+	  "-/_"
+	  "abcdefghijklmnopqrstuvwxyz"
+	  "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+	/* Non-control chars in the POSIX portable character set,
+	   excluding the benign characters.  */
+	static char const printable_and_not_benign[] =
+	  " !\"#$%&'()*+,.0123456789:;<=>?@[\\]^`{|}~";
+
+	register char const *component = name;
+	for (cp = name; *cp; cp++) {
+		unsigned char c = *cp;
+		if (noise && !strchr(benign, c)) {
+			warning((strchr(printable_and_not_benign, c)
+				 ? _("file name '%s' contains byte '%c'")
+				 : _("file name '%s' contains byte '\\%o'")),
+				name, c);
+		}
+		if (c == '/') {
+			if (!componentcheck(name, component, cp))
+			  return false;
+			component = cp + 1;
+		}
+	}
+	return componentcheck(name, component, cp);
+}
+
+static char *
+relname(char const *dir, char const *base)
+{
+  if (*base == '/')
+    return ecpyalloc(base);
+  else {
+    size_t dir_len = strlen(dir);
+    bool needs_slash = dir_len && dir[dir_len - 1] != '/';
+    char *result = emalloc(dir_len + needs_slash + strlen(base) + 1);
+    result[dir_len] = '/';
+    strcpy(result + dir_len + needs_slash, base);
+    return memcpy(result, dir, dir_len);
+  }
 }
 
 static void
-dolink(const char *const fromfield, const char *const tofield)
+dolink(char const *fromfield, char const *tofield)
 {
 	register char *	fromname;
 	register char *	toname;
+	register int fromisdir;
 
-	if (fromfield[0] == '/')
-		fromname = ecpyalloc(fromfield);
-	else {
-		fromname = ecpyalloc(directory);
-		fromname = ecatalloc(fromname, "/");
-		fromname = ecatalloc(fromname, fromfield);
-	}
-	if (tofield[0] == '/')
-		toname = ecpyalloc(tofield);
-	else {
-		toname = ecpyalloc(directory);
-		toname = ecatalloc(toname, "/");
-		toname = ecatalloc(toname, tofield);
-	}
+	fromname = relname(directory, fromfield);
+	toname = relname(directory, tofield);
 	/*
 	** We get to be careful here since
 	** there's a fair chance of root running us.
 	*/
-	if (!itsdir(toname))
-		(void) remove(toname);
-	if (link(fromname, toname) != 0
-	    && access(fromname, F_OK) == 0 && !itsdir(fromname)) {
+	fromisdir = itsdir(fromname);
+	if (fromisdir) {
+		char const *e = strerror(fromisdir < 0 ? errno : EPERM);
+		fprintf(stderr, _("%s: link from %s failed: %s"),
+			progname, fromname, e);
+		exit(EXIT_FAILURE);
+	}
+	if (itsdir(toname) <= 0)
+		remove(toname);
+	if (link(fromname, toname) != 0) {
 		int	result;
 
-		if (mkdirs(toname) != 0)
+		if (! mkdirs(toname))
 			exit(EXIT_FAILURE);
 
 		result = link(fromname, toname);
 		if (result != 0) {
 				const char *s = fromfield;
 				const char *t;
+				char *p;
+				size_t dotdots = 0;
 				register char * symlinkcontents = NULL;
 
 				do
@@ -666,13 +780,13 @@ dolink(const char *const fromfield, const char *const tofield)
 				       && ! strncmp (fromfield, tofield,
 						     ++s - fromfield));
 
-				for (s = tofield + (t - fromfield);
-				     (s = strchr(s, '/'));
-				     s++)
-					symlinkcontents =
-						ecatalloc(symlinkcontents,
-						"../");
-				symlinkcontents = ecatalloc(symlinkcontents, t);
+				for (s = tofield + (t - fromfield); *s; s++)
+				  dotdots += *s == '/';
+				symlinkcontents
+				  = emalloc(3 * dotdots + strlen(t) + 1);
+				for (p = symlinkcontents; dotdots-- != 0; p += 3)
+				  memcpy(p, "../", 3);
+				strcpy(p, t);
 				result = symlink(symlinkcontents, toname);
 				if (result == 0)
 warning(_("hard link failed, symbolic link used"));
@@ -684,7 +798,7 @@ warning(_("hard link failed, symbolic link used"));
 			fp = fopen(fromname, "rb");
 			if (!fp) {
 				const char *e = strerror(errno);
-				(void) fprintf(stderr,
+				fprintf(stderr,
 					       _("%s: Can't read %s: %s\n"),
 					       progname, fromname, e);
 				exit(EXIT_FAILURE);
@@ -692,25 +806,15 @@ warning(_("hard link failed, symbolic link used"));
 			tp = fopen(toname, "wb");
 			if (!tp) {
 				const char *e = strerror(errno);
-				(void) fprintf(stderr,
+				fprintf(stderr,
 					       _("%s: Can't create %s: %s\n"),
 					       progname, toname, e);
 				exit(EXIT_FAILURE);
 			}
 			while ((c = getc(fp)) != EOF)
 				putc(c, tp);
-			if (ferror(fp) || fclose(fp)) {
-				(void) fprintf(stderr,
-					       _("%s: Error reading %s\n"),
-					       progname, fromname);
-				exit(EXIT_FAILURE);
-			}
-			if (ferror(tp) || fclose(tp)) {
-				(void) fprintf(stderr,
-					       _("%s: Error writing %s\n"),
-					       progname, toname);
-				exit(EXIT_FAILURE);
-			}
+			close_file(fp, fromname);
+			close_file(tp, toname);
 			warning(_("link failed, copy used"));
 		}
 	}
@@ -720,8 +824,8 @@ warning(_("hard link failed, symbolic link used"));
 
 #define TIME_T_BITS_IN_FILE	64
 
-static const zic_t min_time = (zic_t) -1 << (TIME_T_BITS_IN_FILE - 1);
-static const zic_t max_time = -1 - ((zic_t) -1 << (TIME_T_BITS_IN_FILE - 1));
+static zic_t const min_time = MINVAL (zic_t, TIME_T_BITS_IN_FILE);
+static zic_t const max_time = MAXVAL (zic_t, TIME_T_BITS_IN_FILE);
 
 /* Estimated time of the Big Bang, in seconds since the POSIX epoch.
    rounded downward to the negation of a power of two that is
@@ -753,17 +857,24 @@ static const zic_t max_time = -1 - ((zic_t) -1 << (TIME_T_BITS_IN_FILE - 1));
 
 static const zic_t big_bang_time = BIG_BANG;
 
+/* Return 1 if NAME is a directory, 0 if it's something else, -1 if trouble.  */
 static int
-itsdir(const char *const name)
+itsdir(char const *name)
 {
-	register char *	myname;
-	register int	accres;
-
-	myname = ecpyalloc(name);
-	myname = ecatalloc(myname, "/.");
-	accres = access(myname, F_OK);
-	free(myname);
-	return accres == 0;
+	struct stat st;
+	int res = stat(name, &st);
+	if (res != 0)
+		return res;
+#ifdef S_ISDIR
+	return S_ISDIR(st.st_mode) != 0;
+#else
+	{
+		char *nameslashdot = relname(name, ".");
+		res = stat(nameslashdot, &st);
+		free(nameslashdot);
+		return res == 0;
+	}
+#endif
 }
 
 /*
@@ -790,7 +901,7 @@ associate(void)
 	register int		i, j;
 
 	if (nrules != 0) {
-		(void) qsort(rules, nrules, sizeof *rules, rcomp);
+		qsort(rules, nrules, sizeof *rules, rcomp);
 		for (i = 0; i < nrules - 1; ++i) {
 			if (strcmp(rules[i].r_name,
 				rules[i + 1].r_name) != 0)
@@ -843,12 +954,12 @@ associate(void)
 			*/
 			eat(zp->z_filename, zp->z_linenum);
 			zp->z_stdoff = gethms(zp->z_rule, _("unruly zone"),
-				TRUE);
+				true);
 			/*
 			** Note, though, that if there's no rule,
 			** a '%s' in the format is a bad thing.
 			*/
-			if (strchr(zp->z_format, '%') != 0)
+			if (zp->z_format_specifier == 's')
 				error("%s", _("%s in ruleless zone"));
 		}
 	}
@@ -864,7 +975,7 @@ infile(const char *name)
 	register char *			cp;
 	register const struct lookup *	lp;
 	register int			nfields;
-	register int			wantcont;
+	register bool			wantcont;
 	register int			num;
 	char				buf[BUFSIZ];
 
@@ -874,11 +985,11 @@ infile(const char *name)
 	} else if ((fp = fopen(name, "r")) == NULL) {
 		const char *e = strerror(errno);
 
-		(void) fprintf(stderr, _("%s: Can't open %s: %s\n"),
+		fprintf(stderr, _("%s: Can't open %s: %s\n"),
 			progname, name, e);
 		exit(EXIT_FAILURE);
 	}
-	wantcont = FALSE;
+	wantcont = false;
 	for (num = 1; ; ++num) {
 		eat(name, num);
 		if (fgets(buf, sizeof buf, fp) != buf)
@@ -909,25 +1020,25 @@ infile(const char *name)
 			else switch ((int) (lp->l_value)) {
 				case LC_RULE:
 					inrule(fields, nfields);
-					wantcont = FALSE;
+					wantcont = false;
 					break;
 				case LC_ZONE:
 					wantcont = inzone(fields, nfields);
 					break;
 				case LC_LINK:
 					inlink(fields, nfields);
-					wantcont = FALSE;
+					wantcont = false;
 					break;
 				case LC_LEAP:
 					if (name != leapsec)
-						(void) fprintf(stderr,
-_("%s: Leap line in non leap seconds file %s\n"),
-							progname, name);
+					  warning(_("%s: Leap line in non leap"
+						    " seconds file %s"),
+						  progname, name);
 					else	inleap(fields, nfields);
-					wantcont = FALSE;
+					wantcont = false;
 					break;
 				default:	/* "cannot happen" */
-					(void) fprintf(stderr,
+					fprintf(stderr,
 _("%s: panic: Invalid l_value %d\n"),
 						progname, lp->l_value);
 					exit(EXIT_FAILURE);
@@ -935,18 +1046,7 @@ _("%s: panic: Invalid l_value %d\n"),
 		}
 		free(fields);
 	}
-	if (ferror(fp)) {
-		(void) fprintf(stderr, _("%s: Error reading %s\n"),
-			progname, filename);
-		exit(EXIT_FAILURE);
-	}
-	if (fp != stdin && fclose(fp)) {
-		const char *e = strerror(errno);
-
-		(void) fprintf(stderr, _("%s: Error closing %s: %s\n"),
-			progname, filename, e);
-		exit(EXIT_FAILURE);
-	}
+	close_file(fp, filename);
 	if (wantcont)
 		error(_("expected continuation line not found"));
 }
@@ -960,10 +1060,11 @@ _("%s: panic: Invalid l_value %d\n"),
 */
 
 static zic_t
-gethms(const char *string, const char *const errstring, const int signable)
+gethms(char const *string, char const *errstring, bool signable)
 {
 	zic_t	hh;
 	int	mm, ss, sign;
+	char xs;
 
 	if (string == NULL || *string == '\0')
 		return 0;
@@ -973,12 +1074,12 @@ gethms(const char *string, const char *const errstring, const int signable)
 		sign = -1;
 		++string;
 	} else	sign = 1;
-	if (sscanf(string, scheck(string, "%"SCNdZIC), &hh) == 1)
+	if (sscanf(string, "%"SCNdZIC"%c", &hh, &xs) == 1)
 		mm = ss = 0;
-	else if (sscanf(string, scheck(string, "%"SCNdZIC":%d"), &hh, &mm) == 2)
+	else if (sscanf(string, "%"SCNdZIC":%d%c", &hh, &mm, &xs) == 2)
 		ss = 0;
-	else if (sscanf(string, scheck(string, "%"SCNdZIC":%d:%d"),
-		&hh, &mm, &ss) != 3) {
+	else if (sscanf(string, "%"SCNdZIC":%d:%d%c", &hh, &mm, &ss, &xs)
+		 != 3) {
 			error("%s", errstring);
 			return 0;
 	}
@@ -1000,7 +1101,7 @@ warning(_("values over 24 hours not handled by pre-2007 versions of zic"));
 }
 
 static void
-inrule(register char **const fields, const int nfields)
+inrule(char **fields, int nfields)
 {
 	static struct rule	r;
 
@@ -1014,7 +1115,7 @@ inrule(register char **const fields, const int nfields)
 	}
 	r.r_filename = filename;
 	r.r_linenum = linenum;
-	r.r_stdoff = gethms(fields[RF_STDOFF], _("invalid saved time"), TRUE);
+	r.r_stdoff = gethms(fields[RF_STDOFF], _("invalid saved time"), true);
 	rulesub(&r, fields[RF_LOYEAR], fields[RF_HIYEAR], fields[RF_COMMAND],
 		fields[RF_MONTH], fields[RF_DAY], fields[RF_TOD]);
 	r.r_name = ecpyalloc(fields[RF_NAME]);
@@ -1025,26 +1126,26 @@ inrule(register char **const fields, const int nfields)
 	rules[nrules++] = r;
 }
 
-static int
-inzone(register char **const fields, const int nfields)
+static bool
+inzone(char **fields, int nfields)
 {
 	register int	i;
 
 	if (nfields < ZONE_MINFIELDS || nfields > ZONE_MAXFIELDS) {
 		error(_("wrong number of fields on Zone line"));
-		return FALSE;
+		return false;
 	}
 	if (strcmp(fields[ZF_NAME], TZDEFAULT) == 0 && lcltime != NULL) {
 		error(
 _("\"Zone %s\" line and -l option are mutually exclusive"),
 			TZDEFAULT);
-		return FALSE;
+		return false;
 	}
 	if (strcmp(fields[ZF_NAME], TZDEFRULES) == 0 && psxrules != NULL) {
 		error(
 _("\"Zone %s\" line and -p option are mutually exclusive"),
 			TZDEFRULES);
-		return FALSE;
+		return false;
 	}
 	for (i = 0; i < nzones; ++i)
 		if (zones[i].z_name != NULL &&
@@ -1054,30 +1155,31 @@ _("duplicate zone name %s (file \"%s\", line %d)"),
 					fields[ZF_NAME],
 					zones[i].z_filename,
 					zones[i].z_linenum);
-				return FALSE;
+				return false;
 		}
-	return inzsub(fields, nfields, FALSE);
+	return inzsub(fields, nfields, false);
 }
 
-static int
-inzcont(register char **const fields, const int nfields)
+static bool
+inzcont(char **fields, int nfields)
 {
 	if (nfields < ZONEC_MINFIELDS || nfields > ZONEC_MAXFIELDS) {
 		error(_("wrong number of fields on Zone continuation line"));
-		return FALSE;
+		return false;
 	}
-	return inzsub(fields, nfields, TRUE);
+	return inzsub(fields, nfields, true);
 }
 
-static int
-inzsub(register char **const fields, const int nfields, const int iscont)
+static bool
+inzsub(char **fields, int nfields, bool iscont)
 {
 	register char *		cp;
+	char *			cp1;
 	static struct zone	z;
 	register int		i_gmtoff, i_rule, i_format;
 	register int		i_untilyear, i_untilmonth;
 	register int		i_untilday, i_untiltime;
-	register int		hasuntil;
+	register bool		hasuntil;
 
 	if (iscont) {
 		i_gmtoff = ZFC_GMTOFF;
@@ -1088,7 +1190,9 @@ inzsub(register char **const fields, const int nfields, const int iscont)
 		i_untilday = ZFC_TILDAY;
 		i_untiltime = ZFC_TILTIME;
 		z.z_name = NULL;
-	} else {
+	} else if (!namecheck(fields[ZF_NAME]))
+		return false;
+	else {
 		i_gmtoff = ZF_GMTOFF;
 		i_rule = ZF_RULE;
 		i_format = ZF_FORMAT;
@@ -1100,15 +1204,23 @@ inzsub(register char **const fields, const int nfields, const int iscont)
 	}
 	z.z_filename = filename;
 	z.z_linenum = linenum;
-	z.z_gmtoff = gethms(fields[i_gmtoff], _("invalid UT offset"), TRUE);
+	z.z_gmtoff = gethms(fields[i_gmtoff], _("invalid UT offset"), true);
 	if ((cp = strchr(fields[i_format], '%')) != 0) {
-		if (*++cp != 's' || strchr(cp, '%') != 0) {
+		if ((*++cp != 's' && *cp != 'z') || strchr(cp, '%')
+		    || strchr(fields[i_format], '/')) {
 			error(_("invalid abbreviation format"));
-			return FALSE;
+			return false;
 		}
 	}
 	z.z_rule = ecpyalloc(fields[i_rule]);
-	z.z_format = ecpyalloc(fields[i_format]);
+	z.z_format = cp1 = ecpyalloc(fields[i_format]);
+	z.z_format_specifier = cp ? *cp : '\0';
+	if (z.z_format_specifier == 'z') {
+	  if (noise)
+	    warning(_("format '%s' not handled by pre-2015 versions of zic"),
+		    z.z_format);
+	  cp1[cp - fields[i_format]] = 's';
+	}
 	if (max_format_len < strlen(z.z_format))
 		max_format_len = strlen(z.z_format);
 	hasuntil = nfields > i_untilyear;
@@ -1134,7 +1246,7 @@ inzsub(register char **const fields, const int nfields, const int iscont)
 				error(_(
 "Zone continuation line end time is not after end time of previous line"
 					));
-				return FALSE;
+				return false;
 		}
 	}
 	zones = growalloc(zones, sizeof *zones, nzones, &nzones_alloc);
@@ -1147,7 +1259,7 @@ inzsub(register char **const fields, const int nfields, const int iscont)
 }
 
 static void
-inleap(register char ** const fields, const int nfields)
+inleap(char **fields, int nfields)
 {
 	register const char *		cp;
 	register const struct lookup *	lp;
@@ -1156,6 +1268,7 @@ inleap(register char ** const fields, const int nfields)
 	int				month, day;
 	zic_t				dayoff, tod;
 	zic_t				t;
+	char xs;
 
 	if (nfields != LEAP_FIELDS) {
 		error(_("wrong number of fields on Leap line"));
@@ -1163,7 +1276,7 @@ inleap(register char ** const fields, const int nfields)
 	}
 	dayoff = 0;
 	cp = fields[LP_YEAR];
-	if (sscanf(cp, scheck(cp, "%"SCNdZIC), &year) != 1) {
+	if (sscanf(cp, "%"SCNdZIC"%c", &year, &xs) != 1) {
 		/*
 		** Leapin' Lizards!
 		*/
@@ -1174,7 +1287,7 @@ inleap(register char ** const fields, const int nfields)
 		leapmaxyear = year;
 	if (!leapseen || leapminyear > year)
 		leapminyear = year;
-	leapseen = TRUE;
+	leapseen = true;
 	j = EPOCH_YEAR;
 	while (j != year) {
 		if (year > j) {
@@ -1198,7 +1311,7 @@ inleap(register char ** const fields, const int nfields)
 		++j;
 	}
 	cp = fields[LP_DAY];
-	if (sscanf(cp, scheck(cp, "%d"), &day) != 1 ||
+	if (sscanf(cp, "%d%c", &day, &xs) != 1 ||
 		day <= 0 || day > len_months[isleap(year)][month]) {
 			error(_("invalid day of month"));
 			return;
@@ -1213,23 +1326,23 @@ inleap(register char ** const fields, const int nfields)
 		return;
 	}
 	t = dayoff * SECSPERDAY;
-	tod = gethms(fields[LP_TIME], _("invalid time of day"), FALSE);
+	tod = gethms(fields[LP_TIME], _("invalid time of day"), false);
 	cp = fields[LP_CORR];
 	{
-		register int	positive;
+		register bool	positive;
 		int		count;
 
 		if (strcmp(cp, "") == 0) { /* infile() turns "-" into "" */
-			positive = FALSE;
+			positive = false;
 			count = 1;
 		} else if (strcmp(cp, "--") == 0) {
-			positive = FALSE;
+			positive = false;
 			count = 2;
 		} else if (strcmp(cp, "+") == 0) {
-			positive = TRUE;
+			positive = true;
 			count = 1;
 		} else if (strcmp(cp, "++") == 0) {
-			positive = TRUE;
+			positive = true;
 			count = 2;
 		} else {
 			error(_("illegal CORRECTION field on Leap line"));
@@ -1251,7 +1364,7 @@ inleap(register char ** const fields, const int nfields)
 }
 
 static void
-inlink(register char **const fields, const int nfields)
+inlink(char **fields, int nfields)
 {
 	struct link	l;
 
@@ -1263,10 +1376,8 @@ inlink(register char **const fields, const int nfields)
 		error(_("blank FROM field on Link line"));
 		return;
 	}
-	if (*fields[LF_TO] == '\0') {
-		error(_("blank TO field on Link line"));
-		return;
-	}
+	if (! namecheck(fields[LF_TO]))
+	  return;
 	l.l_filename = filename;
 	l.l_linenum = linenum;
 	l.l_from = ecpyalloc(fields[LF_FROM]);
@@ -1276,50 +1387,47 @@ inlink(register char **const fields, const int nfields)
 }
 
 static void
-rulesub(register struct rule *const rp,
-	const char *const loyearp,
-	const char *const hiyearp,
-	const char *const typep,
-	const char *const monthp,
-	const char *const dayp,
-	const char *const timep)
+rulesub(struct rule *rp, const char *loyearp, const char *hiyearp,
+	const char *typep, const char *monthp, const char *dayp,
+	const char *timep)
 {
 	register const struct lookup *	lp;
 	register const char *		cp;
 	register char *			dp;
 	register char *			ep;
+	char xs;
 
 	if ((lp = byword(monthp, mon_names)) == NULL) {
 		error(_("invalid month name"));
 		return;
 	}
 	rp->r_month = lp->l_value;
-	rp->r_todisstd = FALSE;
-	rp->r_todisgmt = FALSE;
+	rp->r_todisstd = false;
+	rp->r_todisgmt = false;
 	dp = ecpyalloc(timep);
 	if (*dp != '\0') {
 		ep = dp + strlen(dp) - 1;
 		switch (lowerit(*ep)) {
 			case 's':	/* Standard */
-				rp->r_todisstd = TRUE;
-				rp->r_todisgmt = FALSE;
+				rp->r_todisstd = true;
+				rp->r_todisgmt = false;
 				*ep = '\0';
 				break;
 			case 'w':	/* Wall */
-				rp->r_todisstd = FALSE;
-				rp->r_todisgmt = FALSE;
+				rp->r_todisstd = false;
+				rp->r_todisgmt = false;
 				*ep = '\0';
 				break;
 			case 'g':	/* Greenwich */
 			case 'u':	/* Universal */
 			case 'z':	/* Zulu */
-				rp->r_todisstd = TRUE;
-				rp->r_todisgmt = TRUE;
+				rp->r_todisstd = true;
+				rp->r_todisgmt = true;
 				*ep = '\0';
 				break;
 		}
 	}
-	rp->r_tod = gethms(dp, _("invalid time of day"), FALSE);
+	rp->r_tod = gethms(dp, _("invalid time of day"), false);
 	free(dp);
 	/*
 	** Year work.
@@ -1335,11 +1443,11 @@ rulesub(register struct rule *const rp,
 			rp->r_loyear = ZIC_MAX;
 			break;
 		default:	/* "cannot happen" */
-			(void) fprintf(stderr,
+			fprintf(stderr,
 				_("%s: panic: Invalid l_value %d\n"),
 				progname, lp->l_value);
 			exit(EXIT_FAILURE);
-	} else if (sscanf(cp, scheck(cp, "%"SCNdZIC), &rp->r_loyear) != 1) {
+	} else if (sscanf(cp, "%"SCNdZIC"%c", &rp->r_loyear, &xs) != 1) {
 		error(_("invalid starting year"));
 		return;
 	}
@@ -1357,11 +1465,11 @@ rulesub(register struct rule *const rp,
 			rp->r_hiyear = rp->r_loyear;
 			break;
 		default:	/* "cannot happen" */
-			(void) fprintf(stderr,
+			fprintf(stderr,
 				_("%s: panic: Invalid l_value %d\n"),
 				progname, lp->l_value);
 			exit(EXIT_FAILURE);
-	} else if (sscanf(cp, scheck(cp, "%"SCNdZIC), &rp->r_hiyear) != 1) {
+	} else if (sscanf(cp, "%"SCNdZIC"%c", &rp->r_hiyear, &xs) != 1) {
 		error(_("invalid ending year"));
 		return;
 	}
@@ -1414,7 +1522,7 @@ rulesub(register struct rule *const rp,
 			}
 			rp->r_wday = lp->l_value;
 		}
-		if (sscanf(ep, scheck(ep, "%d"), &rp->r_dayofmonth) != 1 ||
+		if (sscanf(ep, "%d%c", &rp->r_dayofmonth, &xs) != 1 ||
 			rp->r_dayofmonth <= 0 ||
 			(rp->r_dayofmonth > len_months[1][rp->r_month])) {
 				error(_("invalid day of month"));
@@ -1453,7 +1561,7 @@ puttzcode(const int_fast32_t val, FILE *const fp)
 	char	buf[4];
 
 	convert(val, buf);
-	(void) fwrite(buf, sizeof buf, 1, fp);
+	fwrite(buf, sizeof buf, 1, fp);
 }
 
 static void
@@ -1462,7 +1570,7 @@ puttzcode64(const zic_t val, FILE *const fp)
 	char	buf[8];
 
 	convert64(val, buf);
-	(void) fwrite(buf, sizeof buf, 1, fp);
+	fwrite(buf, sizeof buf, 1, fp);
 }
 
 static int
@@ -1474,7 +1582,7 @@ atcomp(const void *avp, const void *bvp)
 	return (a < b) ? -1 : (a > b);
 }
 
-static int
+static bool
 is32(const zic_t x)
 {
 	return INT32_MIN <= x && x <= INT32_MAX;
@@ -1488,7 +1596,7 @@ writezone(const char *const name, const char *const string, char version)
 	register int			leapcnt32, leapi32;
 	register int			timecnt32, timei32;
 	register int			pass;
-	static char *			fullname;
+	char *				fullname;
 	static const struct tzhead	tzh0;
 	static struct tzhead		tzh;
 	zic_t *ats = emalloc(size_product(timecnt, sizeof *ats + 1));
@@ -1499,7 +1607,7 @@ writezone(const char *const name, const char *const string, char version)
 	** Sort.
 	*/
 	if (timecnt > 1)
-		(void) qsort(attypes, timecnt, sizeof *attypes, atcomp);
+		qsort(attypes, timecnt, sizeof *attypes, atcomp);
 	/*
 	** Optimize.
 	*/
@@ -1561,7 +1669,7 @@ writezone(const char *const name, const char *const string, char version)
 		++timei32;
 	}
 	/*
-	** Output an INT32_MIN "transition" if appropriate--see below.
+	** Output an INT32_MIN "transition" if appropriate; see below.
 	*/
 	if (timei32 > 0 && ats[timei32] > INT32_MIN) {
 		--timei32;
@@ -1573,26 +1681,24 @@ writezone(const char *const name, const char *const string, char version)
 		--leapcnt32;
 		++leapi32;
 	}
-	fullname = erealloc(fullname,
-			    strlen(directory) + 1 + strlen(name) + 1);
-	(void) sprintf(fullname, "%s/%s", directory, name);
+	fullname = relname(directory, name);
 	/*
 	** Remove old file, if any, to snap links.
 	*/
-	if (!itsdir(fullname) && remove(fullname) != 0 && errno != ENOENT) {
+	if (itsdir(fullname) <= 0 && remove(fullname) != 0 && errno != ENOENT) {
 		const char *e = strerror(errno);
 
-		(void) fprintf(stderr, _("%s: Can't remove %s: %s\n"),
+		fprintf(stderr, _("%s: Can't remove %s: %s\n"),
 			progname, fullname, e);
 		exit(EXIT_FAILURE);
 	}
 	if ((fp = fopen(fullname, "wb")) == NULL) {
-		if (mkdirs(fullname) != 0)
+		if (! mkdirs(fullname))
 			exit(EXIT_FAILURE);
 		if ((fp = fopen(fullname, "wb")) == NULL) {
 			const char *e = strerror(errno);
 
-			(void) fprintf(stderr, _("%s: Can't create %s: %s\n"),
+			fprintf(stderr, _("%s: Can't create %s: %s\n"),
 				progname, fullname, e);
 			exit(EXIT_FAILURE);
 		}
@@ -1606,7 +1712,7 @@ writezone(const char *const name, const char *const string, char version)
 		register int	thistypecnt;
 		char		thischars[TZ_MAX_CHARS];
 		char		thischarcnt;
-		int 		indmap[TZ_MAX_CHARS];
+		int		indmap[TZ_MAX_CHARS];
 
 		if (pass == 1) {
 			thistimei = timei32;
@@ -1629,16 +1735,16 @@ writezone(const char *const name, const char *const string, char version)
 			** (32- or 64-bit) window.
 			*/
 			if (typecnt != 0)
-				writetype[typecnt - 1] = TRUE;
+				writetype[typecnt - 1] = true;
 		} else {
 			for (i = thistimei - 1; i < thistimelim; ++i)
 				if (i >= 0)
-					writetype[types[i]] = TRUE;
+					writetype[types[i]] = true;
 			/*
 			** For America/Godthab and Antarctica/Palmer
 			*/
 			if (thistimei == 0)
-				writetype[0] = TRUE;
+				writetype[0] = true;
 		}
 #ifndef LEAVE_SOME_PRE_2011_SYSTEMS_IN_THE_LURCH
 		/*
@@ -1668,22 +1774,22 @@ writezone(const char *const name, const char *const string, char version)
 					isdsts[mrudst] = -1;
 					type = addtype(gmtoffs[mrudst],
 						&chars[abbrinds[mrudst]],
-						TRUE,
+						true,
 						ttisstds[mrudst],
 						ttisgmts[mrudst]);
-					isdsts[mrudst] = TRUE;
-					writetype[type] = TRUE;
+					isdsts[mrudst] = 1;
+					writetype[type] = true;
 			}
 			if (histd >= 0 && mrustd >= 0 && histd != mrustd &&
 				gmtoffs[histd] != gmtoffs[mrustd]) {
 					isdsts[mrustd] = -1;
 					type = addtype(gmtoffs[mrustd],
 						&chars[abbrinds[mrustd]],
-						FALSE,
+						false,
 						ttisstds[mrustd],
 						ttisgmts[mrustd]);
-					isdsts[mrustd] = FALSE;
-					writetype[type] = TRUE;
+					isdsts[mrustd] = 0;
+					writetype[type] = true;
 			}
 		}
 #endif /* !defined LEAVE_SOME_PRE_2011_SYSTEMS_IN_THE_LURCH */
@@ -1705,15 +1811,15 @@ writezone(const char *const name, const char *const string, char version)
 				if (strcmp(&thischars[j], thisabbr) == 0)
 					break;
 			if (j == thischarcnt) {
-				(void) strcpy(&thischars[(int) thischarcnt],
+				strcpy(&thischars[(int) thischarcnt],
 					thisabbr);
 				thischarcnt += strlen(thisabbr) + 1;
 			}
 			indmap[abbrinds[i]] = j;
 		}
-#define DO(field)	((void) fwrite(tzh.field, sizeof tzh.field, 1, fp))
+#define DO(field)	fwrite(tzh.field, sizeof tzh.field, 1, fp)
 		tzh = tzh0;
-		(void) strncpy(tzh.tzh_magic, TZ_MAGIC, sizeof tzh.tzh_magic);
+		strncpy(tzh.tzh_magic, TZ_MAGIC, sizeof tzh.tzh_magic);
 		tzh.tzh_version[0] = version;
 		convert(thistypecnt, tzh.tzh_ttisgmtcnt);
 		convert(thistypecnt, tzh.tzh_ttisstdcnt);
@@ -1735,7 +1841,7 @@ writezone(const char *const name, const char *const string, char version)
 			if (pass == 1)
 				/*
 				** Output an INT32_MIN "transition"
-				** if appropriate--see above.
+				** if appropriate; see above.
 				*/
 				puttzcode(((ats[i] < INT32_MIN) ?
 					INT32_MIN : ats[i]), fp);
@@ -1744,16 +1850,16 @@ writezone(const char *const name, const char *const string, char version)
 			unsigned char	uc;
 
 			uc = typemap[types[i]];
-			(void) fwrite(&uc, sizeof uc, 1, fp);
+			fwrite(&uc, sizeof uc, 1, fp);
 		}
 		for (i = 0; i < typecnt; ++i)
 			if (writetype[i]) {
 				puttzcode(gmtoffs[i], fp);
-				(void) putc(isdsts[i], fp);
-				(void) putc((unsigned char) indmap[abbrinds[i]], fp);
+				putc(isdsts[i], fp);
+				putc((unsigned char) indmap[abbrinds[i]], fp);
 			}
 		if (thischarcnt != 0)
-			(void) fwrite(thischars, sizeof thischars[0],
+			fwrite(thischars, sizeof thischars[0],
 				      thischarcnt, fp);
 		for (i = thisleapi; i < thisleaplim; ++i) {
 			register zic_t	todo;
@@ -1782,54 +1888,88 @@ writezone(const char *const name, const char *const string, char version)
 		}
 		for (i = 0; i < typecnt; ++i)
 			if (writetype[i])
-				(void) putc(ttisstds[i], fp);
+				putc(ttisstds[i], fp);
 		for (i = 0; i < typecnt; ++i)
 			if (writetype[i])
-				(void) putc(ttisgmts[i], fp);
-	}
-	(void) fprintf(fp, "\n%s\n", string);
-	if (ferror(fp) || fclose(fp)) {
-		(void) fprintf(stderr, _("%s: Error writing %s\n"),
-			progname, fullname);
-		exit(EXIT_FAILURE);
+				putc(ttisgmts[i], fp);
 	}
+	fprintf(fp, "\n%s\n", string);
+	close_file(fp, fullname);
 	free(ats);
+	free(fullname);
 }
 
-static void
-doabbr(char *const abbr, const char *const format, const char *const letters,
-       const int isdst, const int doquotes)
+static char const *
+abbroffset(char *buf, zic_t offset)
+{
+  char sign = '+';
+  int seconds, minutes;
+
+  if (offset < 0) {
+    offset = -offset;
+    sign = '-';
+  }
+
+  seconds = offset % SECSPERMIN;
+  offset /= SECSPERMIN;
+  minutes = offset % MINSPERHOUR;
+  offset /= MINSPERHOUR;
+  if (100 <= offset) {
+    error(_("%%z UTC offset magnitude exceeds 99:59:59"));
+    return "%z";
+  } else {
+    char *p = buf;
+    *p++ = sign;
+    *p++ = '0' + offset / 10;
+    *p++ = '0' + offset % 10;
+    if (minutes | seconds) {
+      *p++ = '0' + minutes / 10;
+      *p++ = '0' + minutes % 10;
+      if (seconds) {
+	*p++ = '0' + seconds / 10;
+	*p++ = '0' + seconds % 10;
+      }
+    }
+    *p = '\0';
+    return buf;
+  }
+}
+
+static size_t
+doabbr(char *abbr, struct zone const *zp, char const *letters,
+       zic_t stdoff, bool doquotes)
 {
 	register char *	cp;
 	register char *	slashp;
-	register int	len;
+	register size_t	len;
+	char const *format = zp->z_format;
 
 	slashp = strchr(format, '/');
 	if (slashp == NULL) {
-		if (letters == NULL)
-			(void) strcpy(abbr, format);
-		else	(void) sprintf(abbr, format, letters);
-	} else if (isdst) {
-		(void) strcpy(abbr, slashp + 1);
+	  char letterbuf[PERCENT_Z_LEN_BOUND + 1];
+	  if (zp->z_format_specifier == 'z')
+	    letters = abbroffset(letterbuf, zp->z_gmtoff + stdoff);
+	  else if (!letters)
+	    letters = "%s";
+	  sprintf(abbr, format, letters);
+	} else if (stdoff != 0) {
+		strcpy(abbr, slashp + 1);
 	} else {
-		if (slashp > format)
-			(void) strncpy(abbr, format, slashp - format);
+		memcpy(abbr, format, slashp - format);
 		abbr[slashp - format] = '\0';
 	}
-	if (!doquotes)
-		return;
-	for (cp = abbr; *cp != '\0'; ++cp)
-		if (strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZ", *cp) == NULL &&
-			strchr("abcdefghijklmnopqrstuvwxyz", *cp) == NULL)
-				break;
 	len = strlen(abbr);
+	if (!doquotes)
+		return len;
+	for (cp = abbr; is_alpha(*cp); cp++)
+		continue;
 	if (len > 0 && *cp == '\0')
-		return;
+		return len;
 	abbr[len + 2] = '\0';
 	abbr[len + 1] = '>';
-	for ( ; len > 0; --len)
-		abbr[len] = abbr[len - 1];
+	memmove(abbr + 1, abbr, len);
 	abbr[0] = '<';
+	return len + 2;
 }
 
 static void
@@ -1847,11 +1987,12 @@ stringoffset(char *result, zic_t offset)
 	register int	hours;
 	register int	minutes;
 	register int	seconds;
+	bool negative = offset < 0;
+	int len = negative;
 
-	result[0] = '\0';
-	if (offset < 0) {
-		(void) strcpy(result, "-");
+	if (negative) {
 		offset = -offset;
+		result[0] = '-';
 	}
 	seconds = offset % SECSPERMIN;
 	offset /= SECSPERMIN;
@@ -1860,15 +2001,15 @@ stringoffset(char *result, zic_t offset)
 	hours = offset;
 	if (hours >= HOURSPERDAY * DAYSPERWEEK) {
 		result[0] = '\0';
-		return -1;
+		return 0;
 	}
-	(void) sprintf(end(result), "%d", hours);
+	len += sprintf(result + len, "%d", hours);
 	if (minutes != 0 || seconds != 0) {
-		(void) sprintf(end(result), ":%02d", minutes);
+		len += sprintf(result + len, ":%02d", minutes);
 		if (seconds != 0)
-			(void) sprintf(end(result), ":%02d", seconds);
+			len += sprintf(result + len, ":%02d", seconds);
 	}
-	return 0;
+	return len;
 }
 
 static int
@@ -1878,7 +2019,6 @@ stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
 	register zic_t	tod = rp->r_tod;
 	register int	compat = 0;
 
-	result = end(result);
 	if (rp->r_dycode == DC_DOM) {
 		register int	month, total;
 
@@ -1889,9 +2029,9 @@ stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
 			total += len_months[0][month];
 		/* Omit the "J" in Jan and Feb, as that's shorter.  */
 		if (rp->r_month <= 1)
-		  (void) sprintf(result, "%d", total + rp->r_dayofmonth - 1);
+		  result += sprintf(result, "%d", total + rp->r_dayofmonth - 1);
 		else
-		  (void) sprintf(result, "J%d", total + rp->r_dayofmonth);
+		  result += sprintf(result, "J%d", total + rp->r_dayofmonth);
 	} else {
 		register int	week;
 		register int	wday = rp->r_wday;
@@ -1918,16 +2058,16 @@ stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
 		} else	return -1;	/* "cannot happen" */
 		if (wday < 0)
 			wday += DAYSPERWEEK;
-		(void) sprintf(result, "M%d.%d.%d",
-			rp->r_month + 1, week, wday);
+		result += sprintf(result, "M%d.%d.%d",
+				  rp->r_month + 1, week, wday);
 	}
 	if (rp->r_todisgmt)
 		tod += gmtoff;
 	if (rp->r_todisstd && rp->r_stdoff == 0)
 		tod += dstoff;
 	if (tod != 2 * SECSPERMIN * MINSPERHOUR) {
-		(void) strcat(result, "/");
-		if (stringoffset(end(result), tod) != 0)
+		*result++ = '/';
+		if (! stringoffset(result, tod))
 			return -1;
 		if (tod < 0) {
 			if (compat < 2013)
@@ -1967,6 +2107,8 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
 	register const char *		abbrvar;
 	register int			compat = 0;
 	register int			c;
+	size_t				len;
+	int				offsetlen;
 	struct rule			stdr, dstr;
 
 	result[0] = '\0';
@@ -2016,14 +2158,14 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
 			dstr.r_dycode = DC_DOM;
 			dstr.r_dayofmonth = 1;
 			dstr.r_tod = 0;
-			dstr.r_todisstd = dstr.r_todisgmt = FALSE;
+			dstr.r_todisstd = dstr.r_todisgmt = false;
 			dstr.r_stdoff = stdrp->r_stdoff;
 			dstr.r_abbrvar = stdrp->r_abbrvar;
 			stdr.r_month = TM_DECEMBER;
 			stdr.r_dycode = DC_DOM;
 			stdr.r_dayofmonth = 31;
 			stdr.r_tod = SECSPERDAY + stdrp->r_stdoff;
-			stdr.r_todisstd = stdr.r_todisgmt = FALSE;
+			stdr.r_todisstd = stdr.r_todisgmt = false;
 			stdr.r_stdoff = 0;
 			stdr.r_abbrvar
 			  = (stdabbrrp ? stdabbrrp->r_abbrvar : "");
@@ -2034,30 +2176,36 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
 	if (stdrp == NULL && (zp->z_nrules != 0 || zp->z_stdoff != 0))
 		return -1;
 	abbrvar = (stdrp == NULL) ? "" : stdrp->r_abbrvar;
-	doabbr(result, zp->z_format, abbrvar, FALSE, TRUE);
-	if (stringoffset(end(result), -zp->z_gmtoff) != 0) {
+	len = doabbr(result, zp, abbrvar, 0, true);
+	offsetlen = stringoffset(result + len, -zp->z_gmtoff);
+	if (! offsetlen) {
 		result[0] = '\0';
 		return -1;
 	}
+	len += offsetlen;
 	if (dstrp == NULL)
 		return compat;
-	doabbr(end(result), zp->z_format, dstrp->r_abbrvar, TRUE, TRUE);
-	if (dstrp->r_stdoff != SECSPERMIN * MINSPERHOUR)
-		if (stringoffset(end(result),
-			-(zp->z_gmtoff + dstrp->r_stdoff)) != 0) {
-				result[0] = '\0';
-				return -1;
-		}
-	(void) strcat(result, ",");
-	c = stringrule(result, dstrp, dstrp->r_stdoff, zp->z_gmtoff);
+	len += doabbr(result + len, zp, dstrp->r_abbrvar, dstrp->r_stdoff, true);
+	if (dstrp->r_stdoff != SECSPERMIN * MINSPERHOUR) {
+	  offsetlen = stringoffset(result + len,
+				   -(zp->z_gmtoff + dstrp->r_stdoff));
+	  if (! offsetlen) {
+	    result[0] = '\0';
+	    return -1;
+	  }
+	  len += offsetlen;
+	}
+	result[len++] = ',';
+	c = stringrule(result + len, dstrp, dstrp->r_stdoff, zp->z_gmtoff);
 	if (c < 0) {
 		result[0] = '\0';
 		return -1;
 	}
 	if (compat < c)
 		compat = c;
-	(void) strcat(result, ",");
-	c = stringrule(result, stdrp, dstrp->r_stdoff, zp->z_gmtoff);
+	len += strlen(result + len);
+	result[len++] = ',';
+	c = stringrule(result + len, stdrp, dstrp->r_stdoff, zp->z_gmtoff);
 	if (c < 0) {
 		result[0] = '\0';
 		return -1;
@@ -2068,28 +2216,28 @@ stringzone(char *result, const struct zone *const zpfirst, const int zonecount)
 }
 
 static void
-outzone(const struct zone * const zpfirst, const int zonecount)
+outzone(const struct zone *zpfirst, int zonecount)
 {
 	register const struct zone *	zp;
 	register struct rule *		rp;
 	register int			i, j;
-	register int			usestart, useuntil;
+	register bool			usestart, useuntil;
 	register zic_t			starttime, untiltime;
 	register zic_t			gmtoff;
 	register zic_t			stdoff;
 	register zic_t			year;
 	register zic_t			startoff;
-	register int			startttisstd;
-	register int			startttisgmt;
+	register bool			startttisstd;
+	register bool			startttisgmt;
 	register int			type;
 	register char *			startbuf;
 	register char *			ab;
 	register char *			envvar;
 	register int			max_abbr_len;
 	register int			max_envvar_len;
-	register int			prodstic; /* all rules are min to max */
+	register bool			prodstic; /* all rules are min to max */
 	register int			compat;
-	register int			do_extend;
+	register bool			do_extend;
 	register char			version;
 
 	max_abbr_len = 2 + max_format_len + max_abbrvar_len;
@@ -2110,8 +2258,8 @@ outzone(const struct zone * const zpfirst, const int zonecount)
 	** Thanks to Earl Chew
 	** for noting the need to unconditionally initialize startttisstd.
 	*/
-	startttisstd = FALSE;
-	startttisgmt = FALSE;
+	startttisstd = false;
+	startttisgmt = false;
 	min_year = max_year = EPOCH_YEAR;
 	if (leapseen) {
 		updateminmax(leapminyear);
@@ -2128,7 +2276,7 @@ outzone(const struct zone * const zpfirst, const int zonecount)
 			if (rp->r_hiwasnum)
 				updateminmax(rp->r_hiyear);
 			if (rp->r_lowasnum || rp->r_hiwasnum)
-				prodstic = FALSE;
+				prodstic = false;
 		}
 	}
 	/*
@@ -2208,14 +2356,13 @@ outzone(const struct zone * const zpfirst, const int zonecount)
 		startoff = zp->z_gmtoff;
 		if (zp->z_nrules == 0) {
 			stdoff = zp->z_stdoff;
-			doabbr(startbuf, zp->z_format,
-			       NULL, stdoff != 0, FALSE);
+			doabbr(startbuf, zp, NULL, stdoff, false);
 			type = addtype(oadd(zp->z_gmtoff, stdoff),
 				startbuf, stdoff != 0, startttisstd,
 				startttisgmt);
 			if (usestart) {
 				addtt(starttime, type);
-				usestart = FALSE;
+				usestart = false;
 			} else	addtt(big_bang_time, type);
 		} else for (year = min_year; year <= max_year; ++year) {
 			if (useuntil && year > zp->z_untilrule.r_hiyear)
@@ -2276,42 +2423,51 @@ outzone(const struct zone * const zpfirst, const int zonecount)
 					if (k < 0 || jtime < ktime) {
 						k = j;
 						ktime = jtime;
+					} else if (jtime == ktime) {
+					  char const *dup_rules_msg =
+					    _("two rules for same instant");
+					  eats(zp->z_filename, zp->z_linenum,
+					       rp->r_filename, rp->r_linenum);
+					  warning("%s", dup_rules_msg);
+					  rp = &zp->z_rules[k];
+					  eats(zp->z_filename, zp->z_linenum,
+					       rp->r_filename, rp->r_linenum);
+					  error("%s", dup_rules_msg);
 					}
 				}
 				if (k < 0)
 					break;	/* go on to next year */
 				rp = &zp->z_rules[k];
-				rp->r_todo = FALSE;
+				rp->r_todo = false;
 				if (useuntil && ktime >= untiltime)
 					break;
 				stdoff = rp->r_stdoff;
 				if (usestart && ktime == starttime)
-					usestart = FALSE;
+					usestart = false;
 				if (usestart) {
 					if (ktime < starttime) {
 						startoff = oadd(zp->z_gmtoff,
 							stdoff);
-						doabbr(startbuf, zp->z_format,
+						doabbr(startbuf, zp,
 							rp->r_abbrvar,
-							rp->r_stdoff != 0,
-							FALSE);
+							rp->r_stdoff,
+							false);
 						continue;
 					}
 					if (*startbuf == '\0' &&
 						startoff == oadd(zp->z_gmtoff,
 						stdoff)) {
 							doabbr(startbuf,
-								zp->z_format,
+								zp,
 								rp->r_abbrvar,
-								rp->r_stdoff !=
-								0,
-								FALSE);
+								rp->r_stdoff,
+								false);
 					}
 				}
 				eats(zp->z_filename, zp->z_linenum,
 					rp->r_filename, rp->r_linenum);
-				doabbr(ab, zp->z_format, rp->r_abbrvar,
-					rp->r_stdoff != 0, FALSE);
+				doabbr(ab, zp, rp->r_abbrvar,
+				       rp->r_stdoff, false);
 				offset = oadd(zp->z_gmtoff, rp->r_stdoff);
 				type = addtype(offset, ab, rp->r_stdoff != 0,
 					rp->r_todisstd, rp->r_todisgmt);
@@ -2323,7 +2479,7 @@ outzone(const struct zone * const zpfirst, const int zonecount)
 				zp->z_format != NULL &&
 				strchr(zp->z_format, '%') == NULL &&
 				strchr(zp->z_format, '/') == NULL)
-					(void) strcpy(startbuf, zp->z_format);
+					strcpy(startbuf, zp->z_format);
 			eat(zp->z_filename, zp->z_linenum);
 			if (*startbuf == '\0')
 error(_("can't determine time zone abbreviation to use just after until time"));
@@ -2369,7 +2525,7 @@ error(_("can't determine time zone abbreviation to use just after until time"));
 		if (lastat->at < rpytime(&xr, max_year - 1)) {
 			/*
 			** Create new type code for the redundant entry,
-			** to prevent it being optimised away.
+			** to prevent it being optimized away.
 			*/
 			if (typecnt >= TZ_MAX_TYPES) {
 				error(_("too many local time types"));
@@ -2391,7 +2547,7 @@ error(_("can't determine time zone abbreviation to use just after until time"));
 }
 
 static void
-addtt(const zic_t starttime, int type)
+addtt(zic_t starttime, int type)
 {
 	if (starttime <= big_bang_time ||
 		(timecnt == 1 && attypes[0].at < big_bang_time)) {
@@ -2400,7 +2556,7 @@ addtt(const zic_t starttime, int type)
 		ttisstds[0] = ttisstds[type];
 		ttisgmts[0] = ttisgmts[type];
 		if (abbrinds[type] != 0)
-			(void) strcpy(chars, &chars[abbrinds[type]]);
+			strcpy(chars, &chars[abbrinds[type]]);
 		abbrinds[0] = 0;
 		charcnt = strlen(chars) + 1;
 		typecnt = 1;
@@ -2414,23 +2570,10 @@ addtt(const zic_t starttime, int type)
 }
 
 static int
-addtype(const zic_t gmtoff, const char *const abbr, const int isdst,
-	const int ttisstd, const int ttisgmt)
+addtype(zic_t gmtoff, char const *abbr, bool isdst, bool ttisstd, bool ttisgmt)
 {
 	register int	i, j;
 
-	if (isdst != TRUE && isdst != FALSE) {
-		error(_("internal error - addtype called with bad isdst"));
-		exit(EXIT_FAILURE);
-	}
-	if (ttisstd != TRUE && ttisstd != FALSE) {
-		error(_("internal error - addtype called with bad ttisstd"));
-		exit(EXIT_FAILURE);
-	}
-	if (ttisgmt != TRUE && ttisgmt != FALSE) {
-		error(_("internal error - addtype called with bad ttisgmt"));
-		exit(EXIT_FAILURE);
-	}
 	/*
 	** See if there's already an entry for this zone type.
 	** If so, just return its index.
@@ -2470,7 +2613,7 @@ addtype(const zic_t gmtoff, const char *const abbr, const int isdst,
 }
 
 static void
-leapadd(const zic_t t, const int positive, const int rolling, int count)
+leapadd(zic_t t, bool positive, int rolling, int count)
 {
 	register int	i, j;
 
@@ -2514,64 +2657,106 @@ adjleap(void)
 	}
 }
 
-static int
-yearistype(const int year, const char *const type)
+static bool
+yearistype(int year, const char *type)
 {
 	static char *	buf;
 	int		result;
 
 	if (type == NULL || *type == '\0')
-		return TRUE;
+		return true;
 	buf = erealloc(buf, 132 + strlen(yitcommand) + strlen(type));
-	(void) sprintf(buf, "%s %d %s", yitcommand, year, type);
+	sprintf(buf, "%s %d %s", yitcommand, year, type);
 	result = system(buf);
 	if (WIFEXITED(result)) switch (WEXITSTATUS(result)) {
 		case 0:
-			return TRUE;
+			return true;
 		case 1:
-			return FALSE;
+			return false;
 	}
 	error(_("Wild result from command execution"));
-	(void) fprintf(stderr, _("%s: command was '%s', result was %d\n"),
+	fprintf(stderr, _("%s: command was '%s', result was %d\n"),
 		progname, buf, result);
 	for ( ; ; )
 		exit(EXIT_FAILURE);
 }
 
-static int
-lowerit(int a)
+/* Is A a space character in the C locale?  */
+static bool
+is_space(char a)
+{
+	switch (a) {
+	  default:
+		return false;
+	  case ' ': case '\f': case '\n': case '\r': case '\t': case '\v':
+		return true;
+	}
+}
+
+/* Is A an alphabetic character in the C locale?  */
+static bool
+is_alpha(char a)
 {
-	a = (unsigned char) a;
-	return (isascii(a) && isupper(a)) ? tolower(a) : a;
+	switch (a) {
+	  default:
+		return false;
+	  case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
+	  case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
+	  case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
+	  case 'V': case 'W': case 'X': case 'Y': case 'Z':
+	  case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
+	  case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
+	  case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u':
+	  case 'v': case 'w': case 'x': case 'y': case 'z':
+		return true;
+	}
+}
+
+/* If A is an uppercase character in the C locale, return its lowercase
+   counterpart.  Otherwise, return A.  */
+static char
+lowerit(char a)
+{
+	switch (a) {
+	  default: return a;
+	  case 'A': return 'a'; case 'B': return 'b'; case 'C': return 'c';
+	  case 'D': return 'd'; case 'E': return 'e'; case 'F': return 'f';
+	  case 'G': return 'g'; case 'H': return 'h'; case 'I': return 'i';
+	  case 'J': return 'j'; case 'K': return 'k'; case 'L': return 'l';
+	  case 'M': return 'm'; case 'N': return 'n'; case 'O': return 'o';
+	  case 'P': return 'p'; case 'Q': return 'q'; case 'R': return 'r';
+	  case 'S': return 's'; case 'T': return 't'; case 'U': return 'u';
+	  case 'V': return 'v'; case 'W': return 'w'; case 'X': return 'x';
+	  case 'Y': return 'y'; case 'Z': return 'z';
+	}
 }
 
 /* case-insensitive equality */
-static ATTRIBUTE_PURE int
+static ATTRIBUTE_PURE bool
 ciequal(register const char *ap, register const char *bp)
 {
 	while (lowerit(*ap) == lowerit(*bp++))
 		if (*ap++ == '\0')
-			return TRUE;
-	return FALSE;
+			return true;
+	return false;
 }
 
-static ATTRIBUTE_PURE int
+static ATTRIBUTE_PURE bool
 itsabbr(register const char *abbr, register const char *word)
 {
 	if (lowerit(*abbr) != lowerit(*word))
-		return FALSE;
+		return false;
 	++word;
 	while (*++abbr != '\0')
 		do {
 			if (*word == '\0')
-				return FALSE;
+				return false;
 		} while (lowerit(*word++) != lowerit(*abbr));
-	return TRUE;
+	return true;
 }
 
 static ATTRIBUTE_PURE const struct lookup *
-byword(register const char *const word,
-       register const struct lookup *const table)
+byword(const char *word, const struct lookup *table)
 {
 	register const struct lookup *	foundlp;
 	register const struct lookup *	lp;
@@ -2609,8 +2794,7 @@ getfields(register char *cp)
 	array = emalloc(size_product(strlen(cp) + 1, sizeof *array));
 	nsubs = 0;
 	for ( ; ; ) {
-		while (isascii((unsigned char) *cp) &&
-			isspace((unsigned char) *cp))
+		while (is_space(*cp))
 				++cp;
 		if (*cp == '\0' || *cp == '#')
 			break;
@@ -2627,9 +2811,8 @@ getfields(register char *cp)
 						));
 					exit(1);
 				}
-		} while (*cp != '\0' && *cp != '#' &&
-			(!isascii(*cp) || !isspace((unsigned char) *cp)));
-		if (isascii(*cp) && isspace((unsigned char) *cp))
+		} while (*cp && *cp != '#' && !is_space(*cp));
+		if (is_space(*cp))
 			++cp;
 		*dp = '\0';
 	}
@@ -2637,37 +2820,47 @@ getfields(register char *cp)
 	return array;
 }
 
+static _Noreturn void
+time_overflow(void)
+{
+  error(_("time overflow"));
+  exit(EXIT_FAILURE);
+}
+
 static ATTRIBUTE_PURE zic_t
-oadd(const zic_t t1, const zic_t t2)
+oadd(zic_t t1, zic_t t2)
 {
-	if (t1 < 0 ? t2 < ZIC_MIN - t1 : ZIC_MAX - t1 < t2) {
-		error(_("time overflow"));
-		exit(EXIT_FAILURE);
-	}
+	if (t1 < 0 ? t2 < ZIC_MIN - t1 : ZIC_MAX - t1 < t2)
+	  time_overflow();
 	return t1 + t2;
 }
 
 static ATTRIBUTE_PURE zic_t
-tadd(const zic_t t1, const zic_t t2)
+tadd(zic_t t1, zic_t t2)
 {
-	if (t1 == max_time && t2 > 0)
-		return max_time;
-	if (t1 == min_time && t2 < 0)
-		return min_time;
-	if (t1 < 0 ? t2 < min_time - t1 : max_time - t1 < t2) {
-		error(_("time overflow"));
-		exit(EXIT_FAILURE);
-	}
-	return t1 + t2;
+  if (t1 < 0) {
+    if (t2 < min_time - t1) {
+      if (t1 != min_time)
+	time_overflow();
+      return min_time;
+    }
+  } else {
+    if (max_time - t1 < t2) {
+      if (t1 != max_time)
+	time_overflow();
+      return max_time;
+    }
+  }
+  return t1 + t2;
 }
 
 /*
-** Given a rule, and a year, compute the date - in seconds since January 1,
-** 1970, 00:00 LOCAL time - in that year that the rule refers to.
+** Given a rule, and a year, compute the date (in seconds since January 1,
+** 1970, 00:00 LOCAL time) in that year that the rule refers to.
 */
 
 static zic_t
-rpytime(register const struct rule *const rp, register const zic_t wantedy)
+rpytime(const struct rule *rp, zic_t wantedy)
 {
 	register int	m, i;
 	register zic_t	dayoff;			/* with a nod to Margaret O. */
@@ -2735,7 +2928,7 @@ rpytime(register const struct rule *const rp, register const zic_t wantedy)
 			}
 		if (i < 0 || i >= len_months[isleap(y)][m]) {
 			if (noise)
-				warning(_("rule goes past start/end of month--\
+				warning(_("rule goes past start/end of month; \
 will not work with pre-2004 versions of zic"));
 		}
 	}
@@ -2748,7 +2941,7 @@ will not work with pre-2004 versions of zic"));
 }
 
 static void
-newabbr(const char *const string)
+newabbr(const char *string)
 {
 	register int	i;
 
@@ -2756,29 +2949,15 @@ newabbr(const char *const string)
 		register const char *	cp;
 		const char *		mp;
 
-		/*
-		** Want one to ZIC_MAX_ABBR_LEN_WO_WARN alphabetics
-		** optionally followed by a + or - and a number from 1 to 14.
-		*/
 		cp = string;
 		mp = NULL;
-		while (isascii((unsigned char) *cp) &&
-			isalpha((unsigned char) *cp))
+		while (is_alpha(*cp) || ('0' <= *cp && *cp <= '9')
+		       || *cp == '-' || *cp == '+')
 				++cp;
-		if (cp - string == 0)
-mp = _("time zone abbreviation lacks alphabetic at start");
 		if (noise && cp - string < 3)
-mp = _("time zone abbreviation has fewer than 3 alphabetics");
+		  mp = _("time zone abbreviation has fewer than 3 characters");
 		if (cp - string > ZIC_MAX_ABBR_LEN_WO_WARN)
-mp = _("time zone abbreviation has too many alphabetics");
-		if (mp == NULL && (*cp == '+' || *cp == '-')) {
-			++cp;
-			if (isascii((unsigned char) *cp) &&
-				isdigit((unsigned char) *cp))
-					if (*cp++ == '1' &&
-						*cp >= '0' && *cp <= '4')
-							++cp;
-		}
+		  mp = _("time zone abbreviation has too many characters");
 		if (*cp != '\0')
 mp = _("time zone abbreviation differs from POSIX standard");
 		if (mp != NULL)
@@ -2789,18 +2968,18 @@ mp = _("time zone abbreviation differs from POSIX standard");
 		error(_("too many, or too long, time zone abbreviations"));
 		exit(EXIT_FAILURE);
 	}
-	(void) strcpy(&chars[charcnt], string);
+	strcpy(&chars[charcnt], string);
 	charcnt += i;
 }
 
-static int
+static bool
 mkdirs(char *argname)
 {
 	register char *	name;
 	register char *	cp;
 
 	if (argname == NULL || *argname == '\0')
-		return 0;
+		return true;
 	cp = name = ecpyalloc(argname);
 	while ((cp = strchr(cp + 1, '/')) != 0) {
 		*cp = '\0';
@@ -2808,37 +2987,29 @@ mkdirs(char *argname)
 		/*
 		** DOS drive specifier?
 		*/
-		if (isalpha((unsigned char) name[0]) &&
-			name[1] == ':' && name[2] == '\0') {
+		if (is_alpha(name[0]) && name[1] == ':' && name[2] == '\0') {
 				*cp = '/';
 				continue;
 		}
 #endif
-		if (!itsdir(name)) {
-			/*
-			** It doesn't seem to exist, so we try to create it.
-			** Creation may fail because of the directory being
-			** created by some other multiprocessor, so we get
-			** to do extra checking.
-			*/
-			if (mkdir(name, MKDIR_UMASK) != 0) {
-				const char *e = strerror(errno);
-
-				if (errno != EEXIST || !itsdir(name)) {
-					(void) fprintf(stderr,
-_("%s: Can't create directory %s: %s\n"),
-						progname, name, e);
-					free(name);
-					return -1;
-				}
+		/*
+		** Try to create it.  It's OK if creation fails because
+		** the directory already exists, perhaps because some
+		** other process just created it.
+		*/
+		if (mkdir(name, MKDIR_UMASK) != 0) {
+			int err = errno;
+			if (itsdir(name) <= 0) {
+				char const *e = strerror(err);
+				warning(_("%s: Can't create directory"
+					  " %s: %s"),
+					progname, name, e);
+				free(name);
+				return false;
 			}
 		}
 		*cp = '/';
 	}
 	free(name);
-	return 0;
+	return true;
 }
-
-/*
-** UNIX was a registered trademark of The Open Group in 2003.
-*/