Index: contrib/libxo/libxo/libxo.c
===================================================================
--- contrib/libxo/libxo/libxo.c
+++ contrib/libxo/libxo/libxo.c
@@ -78,8 +78,10 @@
     unsigned short xo_style;	/* XO_STYLE_* value */
     unsigned short xo_indent;	/* Indent level (if pretty) */
     unsigned short xo_indent_by; /* Indent amount (tab stop) */
+    xo_flush_func_t xo_flush;	/* Flush callback */
     xo_write_func_t xo_write;	/* Write callback */
     xo_close_func_t xo_close;	/* Close callback */
+    xo_getlinebuf_func_t  xo_getlinebuf;	/* Is file line buffered? */
     xo_formatter_t xo_formatter; /* Custom formating function */
     xo_checkpointer_t xo_checkpointer; /* Custom formating support function */
     void *xo_opaque;		/* Opaque data for write function */
@@ -220,6 +222,27 @@
 xo_anchor_clear (xo_handle_t *xop);
 
 /*
+ * What buffer mode is the underlying file?
+ */
+static int
+xo_getlinebuf_file (void *opaque)
+{
+    FILE *fp = (FILE *) opaque;
+
+    return (__flbf(fp));
+}
+/*
+ * Callback to flush a FILE pointer
+ */
+static int
+xo_flush_file (void *opaque)
+{
+    FILE *fp = (FILE *) opaque;
+
+    return (fflush(fp));
+}
+
+/*
  * Callback to write data to a FILE pointer
  */
 static int
@@ -300,6 +323,8 @@
 {
     xop->xo_opaque = stdout;
     xop->xo_write = xo_write_to_file;
+    xop->xo_flush = xo_flush_file;
+    xop->xo_getlinebuf = xo_getlinebuf_file;
 
     /*
      * We need to initialize the locale, which isn't really pretty.
@@ -1211,7 +1236,7 @@
 	break;
     }
 
-    xo_flush_h(xop);
+    (void)xo_flush_h(xop);
 }
 
 void
@@ -1297,8 +1322,10 @@
 
     if (xop) {
 	xop->xo_opaque = fp;
+	xop->xo_flush = xo_flush_file;
 	xop->xo_write = xo_write_to_file;
 	xop->xo_close = xo_close_file;
+	xop->xo_getlinebuf = xo_getlinebuf_file;
     }
 
     return xop;
@@ -3163,7 +3190,10 @@
     for (cp = fmt; *cp; ) {
 	if (*cp == '\n') {
 	    xo_line_close(xop);
-	    xo_flush_h(xop);
+	    if (xo_getlinebuf_h(xop)) {
+		if (xo_flush_h(xop))
+			return -1;
+	    }
 	    cp += 1;
 	    continue;
 
@@ -4029,13 +4059,14 @@
 
 void
 xo_set_writer (xo_handle_t *xop, void *opaque, xo_write_func_t write_func,
-	       xo_close_func_t close_func)
+	       xo_close_func_t close_func, xo_flush_func_t flush_func)
 {
     xop = xo_default(xop);
 
     xop->xo_opaque = opaque;
     xop->xo_write = write_func;
     xop->xo_close = close_func;
+    xop->xo_flush = flush_func;
 }
 
 void
@@ -4045,7 +4076,7 @@
     xo_free = free_func;
 }
 
-void
+int
 xo_flush_h (xo_handle_t *xop)
 {
     static char div_close[] = "</div>";
@@ -4065,15 +4096,31 @@
     }
 
     xo_write(xop);
+    if (xop->xo_flush == NULL)
+	    return 0;
+
+    return (xop->xo_flush(xop->xo_opaque));
+
 }
 
-void
+int
+xo_getlinebuf_h(xo_handle_t *xop)
+{
+
+    xop = xo_default(xop);
+    if (xop->xo_getlinebuf != NULL)
+	    return (xop->xo_getlinebuf(xop->xo_opaque));
+
+    return (0);
+}
+
+int
 xo_flush (void)
 {
-    xo_flush_h(NULL);
+    return xo_flush_h(NULL);
 }
 
-void
+int
 xo_finish_h (xo_handle_t *xop)
 {
     const char *cp = "";
@@ -4091,13 +4138,13 @@
 	break;
     }
 
-    xo_flush_h(xop);
+    return xo_flush_h(xop);
 }
 
-void
+int
 xo_finish (void)
 {
-    xo_finish_h(NULL);
+    return xo_finish_h(NULL);
 }
 
 /*
Index: contrib/libxo/libxo/xo.h
===================================================================
--- contrib/libxo/libxo/xo.h
+++ contrib/libxo/libxo/xo.h
@@ -69,7 +69,9 @@
 typedef struct xo_handle_s xo_handle_t; /* Handle for XO output */
 
 typedef int (*xo_write_func_t)(void *, const char *);
+typedef int (*xo_flush_func_t)(void *);
 typedef void (*xo_close_func_t)(void *);
+typedef int (*xo_getlinebuf_func_t)(void *);
 typedef void *(*xo_realloc_func_t)(void *, size_t);
 typedef void (*xo_free_func_t)(void *);
 
@@ -93,7 +95,7 @@
 
 void
 xo_set_writer (xo_handle_t *xop, void *opaque, xo_write_func_t write_func,
-	       xo_close_func_t close_func);
+	       xo_close_func_t close_func, xo_flush_func_t flush_func);
 
 void
 xo_set_allocator (xo_realloc_func_t realloc_func, xo_free_func_t free_func);
@@ -227,16 +229,19 @@
 void
 xo_error (const char *fmt, ...);
 
-void
+int
+xo_getlinebuf_h(xo_handle_t *xop);
+
+int
 xo_flush_h (xo_handle_t *xop);
 
-void
+int
 xo_flush (void);
 
-void
+int
 xo_finish_h (xo_handle_t *xop);
 
-void
+int
 xo_finish (void);
 
 void
Index: include/stdio.h
===================================================================
--- include/stdio.h
+++ include/stdio.h
@@ -399,6 +399,7 @@
 char	*fgetln(FILE *, size_t *);
 const char *fmtcheck(const char *, const char *) __format_arg(2);
 int	 fpurge(FILE *);
+int      __flbf(FILE *);
 void	 setbuffer(FILE *, char *, int);
 int	 setlinebuf(FILE *);
 int	 vasprintf(char **, const char *, __va_list)
Index: lib/libc/stdio/Makefile.inc
===================================================================
--- lib/libc/stdio/Makefile.inc
+++ lib/libc/stdio/Makefile.inc
@@ -4,7 +4,7 @@
 # stdio sources
 .PATH: ${LIBC_SRCTOP}/stdio
 
-SRCS+=	_flock_stub.c asprintf.c clrerr.c dprintf.c \
+SRCS+=	__flbf.c _flock_stub.c asprintf.c clrerr.c dprintf.c \
 	fclose.c fcloseall.c fdopen.c \
 	feof.c ferror.c fflush.c fgetc.c fgetln.c fgetpos.c fgets.c fgetwc.c \
 	fgetwln.c fgetws.c \
@@ -79,6 +79,7 @@
 MLINKS+=scanf_l.3 fscanf_l.3 scanf_l.3 sscanf_l.3 scanf_l.3 vfscanf_l.3 \
 	scanf_l.3 vscanf_l.3 scanf_l.3 vsscanf_l.3
 MLINKS+=setbuf.3 setbuffer.3 setbuf.3 setlinebuf.3 setbuf.3 setvbuf.3
+MLINKS+=setbuf.3 __flbf.3
 MLINKS+=tmpnam.3 tempnam.3 tmpnam.3 tmpfile.3
 MLINKS+=wprintf.3 fwprintf.3 wprintf.3 swprintf.3 \
 	wprintf.3 vwprintf.3 wprintf.3 vfwprintf.3 wprintf.3 vswprintf.3
Index: lib/libc/stdio/Symbol.map
===================================================================
--- lib/libc/stdio/Symbol.map
+++ lib/libc/stdio/Symbol.map
@@ -151,6 +151,7 @@
 	wscanf_l;
 	fgetws_l;
 	fputws_l;
+	__flbf;
 	getwc_l;
 	getwchar_l;
 	putwc_l;
Index: lib/libc/stdio/__flbf.c
===================================================================
--- /dev/null
+++ lib/libc/stdio/__flbf.c
@@ -0,0 +1,50 @@
+/*-
+ * Copyright (c) 2014 Norse Corporation
+ * All rights reserved.
+ *
+ * Author: Alfred Perlstein <alfred@freebsd.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#if defined(LIBC_SCCS) && !defined(lint)
+static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
+#endif /* LIBC_SCCS and not lint */
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "namespace.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include "un-namespace.h"
+#include "local.h"
+#include "libc_private.h"
+
+/*
+ * Return if file is line buffered or not.
+ */
+int
+__flbf(FILE * __restrict fp)
+{
+
+	return ((fp->_flags & __SLBF) != 0);
+}
Index: lib/libc/stdio/setbuf.3
===================================================================
--- lib/libc/stdio/setbuf.3
+++ lib/libc/stdio/setbuf.3
@@ -53,6 +53,8 @@
 .Fn setlinebuf "FILE *stream"
 .Ft int
 .Fn setvbuf "FILE * restrict stream" "char * restrict buf" "int mode" "size_t size"
+.Ft int
+.Fn __flbf "FILE * restrict stream"
 .Sh DESCRIPTION
 The three types of buffering available are unbuffered, block buffered,
 and line buffered.
@@ -166,6 +168,13 @@
 is exactly equivalent to the call:
 .Pp
 .Dl "setvbuf(stream, (char *)NULL, _IOLBF, 0);"
+The
+.Pp
+.Fn __flbf
+function returns if the steam is line buffered or not.
+.Fn __flbf
+is a non-standard function and should not be used by code
+that aims to be portable.
 .Sh RETURN VALUES
 The
 .Fn setvbuf
@@ -179,6 +188,9 @@
 function returns what the equivalent
 .Fn setvbuf
 would have returned.
+.Pp
+.Fn __flbf
+returns 1 if the file is line buffered, otherwise it returns 0.
 .Sh SEE ALSO
 .Xr stdbuf 1 ,
 .Xr fclose 3 ,
@@ -195,6 +207,10 @@
 functions
 conform to
 .St -isoC .
+.Pp
+The function
+.Fn __flbf
+is a non-standard function that appears in Solaris and glibc.
 .Sh BUGS
 .Fn setbuf
 usually uses a suboptimal buffer size and should be avoided.