Add compat code for missing wcwidth.

If we don't have wcwidth force fallback implementations of nl_langinfo
and mbtowc.  Based on advice from Ingo Schwarze.

configure.ac

@@ -1721,7 +1721,6 @@ AC_CHECK_FUNCS([ \
 	inet_ntop \
 	innetgr \
 	login_getcapbool \
-	mblen \
 	md5_crypt \
 	memmove \
 	memset_s \
@@ -1789,6 +1788,12 @@ AC_CHECK_FUNCS([ \
 	warn \
 ])
 
+dnl Wide character support.  Linux man page says it needs _XOPEN_SOURCE.
+saved_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -D_XOPEN_SOURCE"
+AC_CHECK_FUNCS([mblen mbtowc nl_langinfo wcwidth])
+CFLAGS="$saved_CFLAGS"
+
 AC_LINK_IFELSE(
         [AC_LANG_PROGRAM(
            [[ #include <ctype.h> ]],

openbsd-compat/bsd-misc.c

@@ -284,3 +284,20 @@ pledge(const char *promises, const char *paths[])
 	return 0;
 }
 #endif
+
+#ifndef HAVE_MBTOWC
+/* a mbtowc that only supports ASCII */
+int
+mbtowc(wchar_t *pwc, const char *s, size_t n)
+{
+	if (s == NULL || *s == '\0')
+		return 0;	/* ASCII is not state-dependent */
+	if (*s < 0 || *s > 0x7f || n < 1) {
+		errno = EOPNOTSUPP;
+		return -1;
+	}
+	if (pwc != NULL)
+		*pwc = *s;
+	return 1;
+}
+#endif

openbsd-compat/openbsd-compat.h

@@ -36,6 +36,8 @@
 
 #include <sys/socket.h>
 
+#include <stddef.h>  /* for wchar_t */
+
 /* OpenBSD function replacements */
 #include "base64.h"
 #include "sigact.h"
@@ -231,6 +233,22 @@ long long strtonum(const char *, long long, long long, const char **);
 # define mblen(x, y)	(1)
 #endif
 
+#ifndef HAVE_WCWIDTH
+# define wcwidth(x)	(((x) >= 0x20 && (x) <= 0x7e) ? 1 : -1)
+/* force our no-op nl_langinfo and mbtowc */
+# undef HAVE_NL_LANGINFO
+# undef HAVE_MBTOWC
+# undef HAVE_LANGINFO_H
+#endif
+
+#ifndef HAVE_NL_LANGINFO
+# define nl_langinfo(x)	""
+#endif
+
+#ifndef HAVE_MBTOWC
+int mbtowc(wchar_t *, const char*, size_t);
+#endif
+
 #if !defined(HAVE_VASPRINTF) || !defined(HAVE_VSNPRINTF)
 # include <stdarg.h>
 #endif