Make the %V{is} extension handle a NULL pointer like %s does: output "(null)"

Add %M{essage} extension which prints an errno value as the
corresponding string if possible or numerically otherwise.

It is not currently possible to do the syslog(3) like %m extension
because errno would need to get capatured on entry to the first
function in the printf family, so %M requires you to supply errno
as an argument.

Add %Q{uote} extension which will print a string in double quotes with
appropriate back-slash escapes (only) if necessary.

include/printf.h

@@ -124,16 +124,28 @@ int register_printf_function(int spec, printf_function *render, printf_arginfo_f
 int register_printf_render(int spec, printf_render *render, printf_arginfo_function *arginfo);
 int register_printf_render_std(const unsigned char *specs);
 
+/* vprintf_errno.c */
+printf_arginfo_function		__printf_arginfo_errno;
+printf_render			__printf_render_errno;
+
 /* vprintf_float.c */
 printf_arginfo_function		__printf_arginfo_float;
 printf_render			__printf_render_float;
 
+/* vprintf_hexdump.c */
+printf_arginfo_function		__printf_arginfo_hexdump;
+printf_render 			__printf_render_hexdump;
+
 /* vprintf_int.c */
 printf_arginfo_function		__printf_arginfo_ptr;
 printf_arginfo_function		__printf_arginfo_int;
 printf_render			__printf_render_ptr;
 printf_render			__printf_render_int;
 
+/* vprintf_quoute.c */
+printf_arginfo_function		__printf_arginfo_quote;
+printf_render 			__printf_render_quote;
+
 /* vprintf_str.c */
 printf_arginfo_function		__printf_arginfo_chr;
 printf_render			__printf_render_chr;
@@ -144,10 +156,6 @@ printf_render			__printf_render_str;
 printf_arginfo_function		__printf_arginfo_time;
 printf_render			__printf_render_time;
 
-/* vprintf_hexdump.c */
-printf_arginfo_function		__printf_arginfo_hexdump;
-printf_render 			__printf_render_hexdump;
-
 /* vprintf_vis.c */
 printf_arginfo_function		__printf_arginfo_vis;
 printf_render 			__printf_render_vis;

lib/libc/stdio/Makefile.inc

@@ -24,7 +24,8 @@ SRCS+=	_flock_stub.c asprintf.c clrerr.c fclose.c fdopen.c feof.c ferror.c \
 	wsetup.c
 
 SRCS+=	xprintf.c xprintf_float.c xprintf_int.c xprintf_str.c
-SRCS+=	xprintf_hexdump.c xprintf_time.c xprintf_vis.c
+SRCS+=	xprintf_errno.c xprintf_hexdump.c xprintf_quote.c 
+SRCS+=	xprintf_time.c xprintf_vis.c
 
 MAN+=	fclose.3 ferror.3 fflush.3 fgetln.3 fgets.3 fgetwln.3 fgetws.3 \
 	flockfile.3 \

lib/libc/stdio/xprintf.c

@@ -655,6 +655,16 @@ register_printf_render_std(const unsigned char *specs)
 			    __printf_render_hexdump,
 			    __printf_arginfo_hexdump);
 			break;
+		case 'M':
+			register_printf_render(*specs,
+			    __printf_render_errno,
+			    __printf_arginfo_errno);
+			break;
+		case 'Q':
+			register_printf_render(*specs,
+			    __printf_render_quote,
+			    __printf_arginfo_quote);
+			break;
 		case 'T':
 			register_printf_render(*specs,
 			    __printf_render_time,

lib/libc/stdio/xprintf_errno.c

@@ -0,0 +1,65 @@
+/*-
+ * Copyright (c) 2005 Poul-Henning Kamp
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#include <namespace.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <wchar.h>
+#include <vis.h>
+#include <assert.h>
+#include <sys/time.h>
+#include "printf.h"
+
+int
+__printf_arginfo_errno(const struct printf_info *pi __unused, size_t n, int *argt)
+{
+
+	assert(n >= 1);
+	argt[0] = PA_INT;
+	return (1);
+}
+
+int
+__printf_render_errno(struct __printf_io *io, const struct printf_info *pi __unused, const void *const *arg)
+{
+	int ret, error;
+	char buf[64];
+	const char *p;
+
+	ret = 0;
+	error = *((const int *)arg[0]);
+	if (error >= 0 && error < sys_nerr) {
+		p = strerror(error);
+		return (__printf_out(io, pi, p, strlen(p)));
+	}
+	sprintf(buf, "errno=%d/0x%x", error, error);
+	ret += __printf_out(io, pi, buf, strlen(buf));
+	__printf_flush(io);
+	return(ret);
+}

lib/libc/stdio/xprintf_quote.c

@@ -0,0 +1,108 @@
+/*-
+ * Copyright (c) 2005 Poul-Henning Kamp
+ * All rights reserved.
+ *
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+#include <namespace.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <wchar.h>
+#include <vis.h>
+#include <assert.h>
+#include <sys/time.h>
+#include "printf.h"
+
+int
+__printf_arginfo_quote(const struct printf_info *pi __unused, size_t n, int *argt)
+{
+
+	assert(n >= 1);
+	argt[0] = PA_POINTER;
+	return (1);
+}
+
+int
+__printf_render_quote(struct __printf_io *io, const struct printf_info *pi __unused, const void *const *arg)
+{
+	const char *str, *p, *t, *o;
+	char *q, *r;
+	int i, ret;
+
+	str = *((const char *const *)arg[0]);
+	if (str == NULL)
+		return (__printf_out(io, pi, "\"(null)\"", 8));
+	i = 0;
+	if (*str == '\0')
+		i++;
+	else if (*str == '#')
+		i++;
+	else {
+		for (p = str; *p; p++)
+			if (isspace(*p) || *p == '\\' || *p == '"')
+				i++;
+	}
+	if (!i) 
+		return (__printf_out(io, pi, str, strlen(str)));
+	
+	q = malloc(strlen(str) * 5);
+	assert(q != NULL);
+	r = q;
+	ret = __printf_out(io, pi, "\"", 1);
+	t = str;
+	for (p = str; *p; p++) {
+		o = NULL;
+		if (*p == '\\')
+			o = "\\\\";
+		else if (*p == '\n')
+			o = "\\n";
+		else if (*p == '\r')
+			o = "\\r";
+		else if (*p == '\t')
+			o = "\\t";
+		else if (*p == ' ')
+			o = " ";
+		else if (*p == '"')
+			o = "\\\"";
+		else if (isspace(*p)) {
+			sprintf(r, "\\%03o", *p);
+			o = r;
+			r += strlen(r) + 1;
+		} else
+			continue;
+		if (p != t) {
+			ret += __printf_out(io, pi, t, p - t);
+			t = p + 1;
+		}
+		ret += __printf_out(io, pi, o, strlen(o));
+	}
+	if (p != t)
+		ret += __printf_out(io, pi, t, p - t);
+	ret += __printf_out(io, pi, "\"", 1);
+	__printf_flush(io);
+	return(ret);
+}

lib/libc/stdio/xprintf_vis.c

@@ -54,6 +54,8 @@ __printf_render_vis(struct __printf_io *io, const struct printf_info *pi, const
 
 	ret = 0;
 	p = *((char **)arg[0]);
+	if (p == NULL)
+		return (__printf_out(io, pi, "(null)", 6));
 	if (pi->prec >= 0)
 		l = pi->prec;
 	else