[PATCH] lib: fix scnprintf() if @size is == 0

[PATCH] lib: fix scnprintf() if @size is == 0

[Changli Gao]

scnprintf() should return 0 if @size is == 0. Update the comment for it,
as @size is unsigned.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
---
 lib/vsprintf.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 7af9d84..0c66ae9 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1497,7 +1497,7 @@ EXPORT_SYMBOL(snprintf);
  * @...: Arguments for the format string
  *
  * The return value is the number of characters written into @buf not including
- * the trailing '\0'. If @size is <= 0 the function returns 0.
+ * the trailing '\0'. If @size is == 0 the function returns 0.
  */
 
 int scnprintf(char *buf, size_t size, const char *fmt, ...)
@@ -1509,7 +1509,7 @@ int scnprintf(char *buf, size_t size, const char *fmt, ...)
 	i = vsnprintf(buf, size, fmt, args);
 	va_end(args);
 
-	return (i >= size) ? (size - 1) : i;
+	return (i >= size) ? (size != 0 ? (size - 1) : 0) : i;
 }
 EXPORT_SYMBOL(scnprintf);
 

Re: [PATCH] lib: fix scnprintf() if @size is == 0

[Joe Perches]

On Wed, 2010-08-25 at 07:35 +0800, Changli Gao wrote:
> scnprintf() should return 0 if @size is == 0. Update the comment for it,
> as @size is unsigned.
> 
> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> ---
>  lib/vsprintf.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 7af9d84..0c66ae9 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1497,7 +1497,7 @@ EXPORT_SYMBOL(snprintf);
>   * @...: Arguments for the format string
>   *
>   * The return value is the number of characters written into @buf not including
> - * the trailing '\0'. If @size is <= 0 the function returns 0.
> + * the trailing '\0'. If @size is == 0 the function returns 0.
>   */
>  
>  int scnprintf(char *buf, size_t size, const char *fmt, ...)
> @@ -1509,7 +1509,7 @@ int scnprintf(char *buf, size_t size, const char *fmt, ...)
>  	i = vsnprintf(buf, size, fmt, args);
>  	va_end(args);
>  
> -	return (i >= size) ? (size - 1) : i;
> +	return (i >= size) ? (size != 0 ? (size - 1) : 0) : i;

Isn't simpler to check size at the beginning of the function?

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 7af9d84..779236f 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1505,6 +1505,9 @@ int scnprintf(char *buf, size_t size, const char *fmt, ...)
 	va_list args;
 	int i;
 
+	if (!size)
+		return 0;
+
 	va_start(args, fmt);
 	i = vsnprintf(buf, size, fmt, args);
 	va_end(args);

Re: [PATCH] lib: fix scnprintf() if @size is == 0

[Changli Gao]

On Wed, Aug 25, 2010 at 8:03 AM, Joe Perches <joe@perches.com> wrote:
>
> Isn't simpler to check size at the beginning of the function?
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 7af9d84..779236f 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1505,6 +1505,9 @@ int scnprintf(char *buf, size_t size, const char *fmt, ...)
>        va_list args;
>        int i;
>
> +       if (!size)
> +               return 0;
> +

It is a rare case, so don't slow down the normal users.

>        va_start(args, fmt);
>        i = vsnprintf(buf, size, fmt, args);
>        va_end(args);
>
>
>



-- 
Regards,
Changli Gao(xiaosuo@gmail.com)

Re: [PATCH] lib: fix scnprintf() if @size is == 0

[Joe Perches]

On Wed, 2010-08-25 at 08:10 +0800, Changli Gao wrote:
> On Wed, Aug 25, 2010 at 8:03 AM, Joe Perches <joe@perches.com> wrote:
> > Isn't simpler to check size at the beginning of the function?
> It is a rare case, so don't slow down the normal users.

That's fine, but I don't like blinking that much
when I read code.

How about:

	if (i < size)
		return i;
	if (size)
		return i - 1;
	return 0;

Re: [PATCH] lib: fix scnprintf() if @size is == 0

[Changli Gao]

On Wed, Aug 25, 2010 at 8:35 AM, Joe Perches <joe@perches.com> wrote:
> On Wed, 2010-08-25 at 08:10 +0800, Changli Gao wrote:
>> On Wed, Aug 25, 2010 at 8:03 AM, Joe Perches <joe@perches.com> wrote:
>> > Isn't simpler to check size at the beginning of the function?
>> It is a rare case, so don't slow down the normal users.
>
> That's fine, but I don't like blinking that much
> when I read code.
>

"? :" isn't friendly. OK, I'll update my patch. Thanks.

-- 
Regards,
Changli Gao(xiaosuo@gmail.com)