libc: make strerror_rl() usable for libc

Reviewed by:	imp
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D44916

lib/libc/include/libc_private.h

@@ -374,5 +374,7 @@ struct __nl_cat_d;
 struct _xlocale;
 struct __nl_cat_d *__catopen_l(const char *name, int type,
 	    struct _xlocale *locale);
+int __strerror_rl(int errnum, char *strerrbuf, size_t buflen,
+	    struct _xlocale *locale);
 
 #endif /* _LIBC_PRIVATE_H_ */

lib/libc/string/strerror.c

@@ -74,8 +74,8 @@ errstr(int num, const char *uprefix, char *buf, size_t len)
 	strlcat(buf, t, len);
 }
 
-static int
-strerror_rl(int errnum, char *strerrbuf, size_t buflen, locale_t locale)
+int
+__strerror_rl(int errnum, char *strerrbuf, size_t buflen, locale_t locale)
 {
 	int retval = 0;
 #if defined(NLS)
@@ -116,7 +116,7 @@ strerror_rl(int errnum, char *strerrbuf, size_t buflen, locale_t locale)
 int
 strerror_r(int errnum, char *strerrbuf, size_t buflen)
 {
-	return (strerror_rl(errnum, strerrbuf, buflen, __get_locale()));
+	return (__strerror_rl(errnum, strerrbuf, buflen, __get_locale()));
 }
 
 char *
@@ -124,7 +124,7 @@ strerror_l(int num, locale_t locale)
 {
 	static _Thread_local char ebuf[NL_TEXTMAX];
 
-	if (strerror_rl(num, ebuf, sizeof(ebuf), locale) != 0)
+	if (__strerror_rl(num, ebuf, sizeof(ebuf), locale) != 0)
 		errno = EINVAL;
 	return (ebuf);
 }
@@ -134,7 +134,7 @@ strerror(int num)
 {
 	static char ebuf[NL_TEXTMAX];
 
-	if (strerror_rl(num, ebuf, sizeof(ebuf), __get_locale()) != 0)
+	if (__strerror_rl(num, ebuf, sizeof(ebuf), __get_locale()) != 0)
 		errno = EINVAL;
 	return (ebuf);
 }