sbuf_new(9) now returns a struct sbuf * instead of an int. If the caller

does not provide a struct sbuf, sbuf_new(9) will allocate one and return
a pointer to it.

share/man/man9/sbuf.9

@@ -45,7 +45,7 @@
 .Sh SYNOPSIS
 .Fd #include <sys/types.h>
 .Fd #include <sys/sbuf.h>
-.Ft int
+.Ft struct sbuf *s
 .Fn sbuf_new "struct sbuf *s" "char *buf" "int length" "int flags"
 .Ft void
 .Fn sbuf_clear "struct sbuf *s"
@@ -85,6 +85,13 @@ The
 function initializes the
 .Fa sbuf
 pointed to by its first argument.
+If that pointer is
+.Dv NULL ,
+.Fn sbuf_new
+allocates a
+.Fa struct sbuf
+using
+.Xr malloc 9 .
 The
 .Fa buf
 argument is a pointer to a buffer in which to store the actual string;
@@ -213,7 +220,10 @@ or it is reinitialized to a sufficiently short string using
 .Fn sbuf_cpy .
 .Sh RETURN VALUES
 .Fn sbuf_new
-returns \-1 if it failed to allocate a storage buffer, and zero
+returns
+.Dv NULL
+if it failed to allocate a storage buffer, and a pointer to the new
+.Fa sbuf
 otherwise.
 .Pp
 .Fn sbuf_setpos

sys/dev/sound/pcm/sound.c

@@ -881,7 +881,7 @@ do_status(int action, struct uio *buf)
 	case 0: /* open */
 		if (status_open)
 			return EBUSY;
-		if (sbuf_new(&s, NULL, 4096, 0))
+		if (sbuf_new(&s, NULL, 4096, 0) == NULL)
 			return ENXIO;
 		bufptr = 0;
 		err = (status_init(&s) > 0)? 0 : ENOMEM;

sys/kern/subr_sbuf.c

@@ -55,6 +55,7 @@ MALLOC_DEFINE(M_SBUF, "sbuf", "string buffers");
  * Predicates
  */
 #define SBUF_ISDYNAMIC(s)	((s)->s_flags & SBUF_DYNAMIC)
+#define SBUF_ISDYNSTRUCT(s)	((s)->s_flags & SBUF_DYNSTRUCT)
 #define SBUF_ISFINISHED(s)	((s)->s_flags & SBUF_FINISHED)
 #define SBUF_HASOVERFLOWED(s)	((s)->s_flags & SBUF_OVERFLOWED)
 #define SBUF_HASROOM(s)		((s)->s_len < (s)->s_size - 1)
@@ -99,27 +100,36 @@ _assert_sbuf_state(char *fun, struct sbuf *s, int state)
  * If buf is non-NULL, it points to a static or already-allocated string
  * big enough to hold at least length characters.
  */
-int
+struct sbuf *
 sbuf_new(struct sbuf *s, char *buf, int length, int flags)
 {
 	KASSERT(length >= 0,
 	    ("attempt to create an sbuf of negative length (%d)", length));
 	KASSERT(flags == 0,
 	    (__FUNCTION__ " called with non-zero flags"));
-	KASSERT(s != NULL,
-	    (__FUNCTION__ " called with a NULL sbuf pointer"));
 
-	bzero(s, sizeof *s);
+	if (s == NULL) {
+		s = (struct sbuf *)SBMALLOC(sizeof *s);
+		if (s == NULL)
+			return (NULL);
+		bzero(s, sizeof *s);
+		SBUF_SETFLAG(s, SBUF_DYNSTRUCT);
+	} else {
+		bzero(s, sizeof *s);
+	}
 	s->s_size = length;
 	if (buf) {
 		s->s_buf = buf;
-		return (0);
+		return (s);
 	}
 	s->s_buf = (char *)SBMALLOC(s->s_size);
-	if (s->s_buf == NULL)
-		return (-1);
+	if (s->s_buf == NULL) {
+		if (SBUF_ISDYNSTRUCT(s))
+			SBFREE(s);
+		return (NULL);
+	}
 	SBUF_SETFLAG(s, SBUF_DYNAMIC);
-	return (0);
+	return (s);
 }
 
 /*
@@ -315,4 +325,6 @@ sbuf_delete(struct sbuf *s)
 	if (SBUF_ISDYNAMIC(s))
 		SBFREE(s->s_buf);
 	bzero(s, sizeof *s);
+	if (SBUF_ISDYNSTRUCT(s))
+		SBFREE(s);
 }

sys/sys/sbuf.h

@@ -43,6 +43,7 @@ struct sbuf {
 #define SBUF_DYNAMIC	0x00010000	/* s_buf must be freed */
 #define SBUF_FINISHED	0x00020000	/* set by sbuf_finish() */
 #define SBUF_OVERFLOWED	0x00040000	/* sbuf overflowed */
+#define SBUF_DYNSTRUCT	0x00080000	/* sbuf must be freed */
 	int		 s_flags;	/* flags */
 };
 
@@ -50,18 +51,18 @@ __BEGIN_DECLS
 /*
  * API functions
  */
-int	 sbuf_new(struct sbuf *s, char *buf, int length, int flags);
-void	 sbuf_clear(struct sbuf *s);
-int	 sbuf_setpos(struct sbuf *s, int pos);
-int	 sbuf_cat(struct sbuf *s, const char *str);
-int	 sbuf_cpy(struct sbuf *s, const char *str);
-int	 sbuf_printf(struct sbuf *s, char *fmt, ...);
-int	 sbuf_putc(struct sbuf *s, int c);
-int	 sbuf_overflowed(struct sbuf *s);
-void	 sbuf_finish(struct sbuf *s);
-char    *sbuf_data(struct sbuf *s);
-int	 sbuf_len(struct sbuf *s);
-void	 sbuf_delete(struct sbuf *s);
+struct sbuf	*sbuf_new(struct sbuf *s, char *buf, int length, int flags);
+void		 sbuf_clear(struct sbuf *s);
+int		 sbuf_setpos(struct sbuf *s, int pos);
+int		 sbuf_cat(struct sbuf *s, const char *str);
+int		 sbuf_cpy(struct sbuf *s, const char *str);
+int		 sbuf_printf(struct sbuf *s, char *fmt, ...);
+int		 sbuf_putc(struct sbuf *s, int c);
+int		 sbuf_overflowed(struct sbuf *s);
+void		 sbuf_finish(struct sbuf *s);
+char		*sbuf_data(struct sbuf *s);
+int		 sbuf_len(struct sbuf *s);
+void		 sbuf_delete(struct sbuf *s);
 __END_DECLS
 
 #endif