diff --git a/lib/libc/locale/mblen.c b/lib/libc/locale/mblen.c
index b5b92d172af3..a54e05111b59 100644
--- a/lib/libc/locale/mblen.c
+++ b/lib/libc/locale/mblen.c
@@ -38,19 +38,18 @@
 __FBSDID("$FreeBSD$");
 
 #include <errno.h>
-#include <stdlib.h>
 #include <stddef.h>
+#include <stdlib.h>
 #include <rune.h>
 
 int
-mblen(s, n)
-	const char *s;
-	size_t n;
+mblen(const char *s, size_t n)
 {
-	char const *e;
+	const char *e;
 
-	if (s == 0 || *s == 0)
-		return (0);	/* No support for state dependent encodings. */
+	if (s == NULL || *s == '\0')
+		/* No support for state dependent encodings. */
+		return (0);	
 
 	if (sgetrune(s, n, &e) == _INVALID_RUNE) {
 		errno = EILSEQ;
diff --git a/lib/libc/locale/mbstowcs.c b/lib/libc/locale/mbstowcs.c
index 3657c832d309..a9adb8ab3321 100644
--- a/lib/libc/locale/mbstowcs.c
+++ b/lib/libc/locale/mbstowcs.c
@@ -44,22 +44,20 @@ __FBSDID("$FreeBSD$");
 #include <rune.h>
 
 size_t
-mbstowcs(pwcs, s, n)
-	wchar_t * __restrict pwcs;
-	const char * __restrict s;
-	size_t n;
+mbstowcs(wchar_t * __restrict pwcs, const char * __restrict s, size_t n)
 {
-	char const *e;
-	int cnt = 0;
+	const char *e;
+	int cnt;
 	rune_t r;
 
-	if (!s) {
+	if (s == NULL) {
 		errno = EINVAL;
 		return (-1);
 	}
 
 	if (pwcs == NULL) {
 		/* Convert and count only, do not store. */
+		cnt = 0;
 		while ((r = sgetrune(s, MB_LEN_MAX, &e)) != _INVALID_RUNE &&
 		    r != 0) {
 			s = e;
@@ -72,13 +70,14 @@ mbstowcs(pwcs, s, n)
 	}
 
 	/* Convert, store and count characters. */
+	cnt = 0;
 	while (n-- > 0) {
 		*pwcs = sgetrune(s, MB_LEN_MAX, &e);
 		if (*pwcs == _INVALID_RUNE) {
 			errno = EILSEQ;
 			return (-1);
 		}
-		if (*pwcs++ == 0)
+		if (*pwcs++ == L'\0')
 			break;
 		s = e;
 		++cnt;
diff --git a/lib/libc/locale/mbtowc.c b/lib/libc/locale/mbtowc.c
index 206a3a3e6336..a690bec171dc 100644
--- a/lib/libc/locale/mbtowc.c
+++ b/lib/libc/locale/mbtowc.c
@@ -43,22 +43,20 @@ __FBSDID("$FreeBSD$");
 #include <rune.h>
 
 int
-mbtowc(pwc, s, n)
-	wchar_t * __restrict pwc;
-	const char * __restrict s;
-	size_t n;
+mbtowc(wchar_t * __restrict pwc, const char * __restrict s, size_t n)
 {
-	char const *e;
+	const char *e;
 	rune_t r;
 
-	if (s == 0 || *s == 0)
-		return (0);	/* No support for state dependent encodings. */
+	if (s == NULL || *s == '\0')
+		/* No support for state dependent encodings. */
+		return (0);	
 
 	if ((r = sgetrune(s, n, &e)) == _INVALID_RUNE) {
 		errno = EILSEQ;
 		return (s - e);
 	}
-	if (pwc)
+	if (pwc != NULL)
 		*pwc = r;
 	return (e - s);
 }
diff --git a/lib/libc/locale/wcstombs.c b/lib/libc/locale/wcstombs.c
index 25652a870756..796e3c217af5 100644
--- a/lib/libc/locale/wcstombs.c
+++ b/lib/libc/locale/wcstombs.c
@@ -44,16 +44,13 @@ __FBSDID("$FreeBSD$");
 #include <rune.h>
 
 size_t
-wcstombs(s, pwcs, n)
-	char * __restrict s;
-	const wchar_t * __restrict pwcs;
-	size_t n;
+wcstombs(char * __restrict s, const wchar_t * __restrict pwcs, size_t n)
 {
 	char buf[MB_LEN_MAX];
 	char *e;
 	int cnt, nb;
 
-	if (!pwcs || n > INT_MAX) {
+	if (pwcs == NULL || n > INT_MAX) {
 		errno = EINVAL;
 		return (-1);
 	}
@@ -63,7 +60,7 @@ wcstombs(s, pwcs, n)
 	if (s == NULL) {
 		/* Convert and count only, do not store. */
 		while (*pwcs != L'\0') {
-			if (!sputrune(*pwcs++, buf, MB_LEN_MAX, &e)) {
+			if (sputrune(*pwcs++, buf, MB_LEN_MAX, &e) == 0) {
 				errno = EILSEQ;
 				return (-1);
 			}
@@ -75,15 +72,15 @@ wcstombs(s, pwcs, n)
 	/* Convert, store and count characters. */
 	nb = n;
 	while (nb > 0) {
-		if (*pwcs == 0) {
-			*s = 0;
+		if (*pwcs == L'\0') {
+			*s = '\0';
 			break;
 		}
-		if (!sputrune(*pwcs++, s, nb, &e)) {
+		if (sputrune(*pwcs++, s, nb, &e) == 0) {
 			errno = EILSEQ;
 			return (-1);
 		}
-		if (!e)			/* too long */
+		if (e == NULL)		/* too long */
 			return (cnt);
 		cnt += e - s;
 		nb -= e - s;
diff --git a/lib/libc/locale/wctomb.c b/lib/libc/locale/wctomb.c
index 2a225f48fa6f..da934b272290 100644
--- a/lib/libc/locale/wctomb.c
+++ b/lib/libc/locale/wctomb.c
@@ -44,17 +44,16 @@ __FBSDID("$FreeBSD$");
 #include <rune.h>
 
 int
-wctomb(s, wchar)
-	char *s;
-	wchar_t wchar;
+wctomb(char *s, wchar_t wchar)
 {
 	char *e;
 
-	if (s == 0)
-		return (0);	/* No support for state dependent encodings. */
+	if (s == NULL)
+		/* No support for state dependent encodings. */
+		return (0);	
 
-	if (wchar == 0) {
-		*s = 0;
+	if (wchar == L'\0') {
+		*s = '\0';
 		return (1);
 	}