Implement the XSI extension which allows the destination string to be

NULL, and returns the number of bytes that would be required to store
the result of the conversion without storing anything.

PR:		17694

1 files changed, 25 insertions, 4 deletions

diff --git a/lib/libc/locale/wcstombs.c b/lib/libc/locale/wcstombs.c
index 987ec30..ed9397a 100644
--- a/lib/libc/locale/wcstombs.c
+++ b/lib/libc/locale/wcstombs.c
@@ -37,6 +37,7 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <errno.h>
 #include <stdlib.h>
 #include <limits.h>
 #include <stddef.h>
@@ -48,26 +49,46 @@ wcstombs(s, pwcs, n)
 	const wchar_t *pwcs;
 	size_t n;
 {
+	char buf[MB_LEN_MAX];
 	char *e;
 	int cnt, nb;
 
-	if (!pwcs || !s || n > INT_MAX)
+	if (!pwcs || n > INT_MAX) {
+		errno = EINVAL;
 		return (-1);
+	}
 
-	nb = n;
 	cnt = 0;
+
+	if (s == NULL) {
+		/* Convert and count only, do not store. */
+		while (*pwcs != L'\0') {
+			if (!sputrune(*pwcs++, buf, MB_LEN_MAX, &e)) {
+				errno = EILSEQ;
+				return (-1);
+			}
+			cnt += e - buf;
+		}
+		return (cnt);
+	}
+
+	/* Convert, store and count characters. */
+	nb = n;
 	while (nb > 0) {
 		if (*pwcs == 0) {
 			*s = 0;
 			break;
 		}
-		if (!sputrune(*pwcs++, s, nb, &e))
-			return (-1);		/* encoding error */
+		if (!sputrune(*pwcs++, s, nb, &e)) {
+			errno = EILSEQ;
+			return (-1);
+		}
 		if (!e)			/* too long */
 			return (cnt);
 		cnt += e - s;
 		nb -= e - s;
 		s = e;
 	}
+
 	return (cnt);
 }