2010-08-24 23:35:38

by Changli Gao

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

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

Signed-off-by: Changli Gao <[email protected]>
---
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);


2010-08-25 00:03:47

by Joe Perches

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

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 <[email protected]>
> ---
> 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);

2010-08-25 00:10:43

by Changli Gao

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

On Wed, Aug 25, 2010 at 8:03 AM, Joe Perches <[email protected]> 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([email protected])

2010-08-25 00:35:45

by Joe Perches

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

On Wed, 2010-08-25 at 08:10 +0800, Changli Gao wrote:
> On Wed, Aug 25, 2010 at 8:03 AM, Joe Perches <[email protected]> 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;

2010-08-25 00:44:55

by Changli Gao

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

On Wed, Aug 25, 2010 at 8:35 AM, Joe Perches <[email protected]> wrote:
> On Wed, 2010-08-25 at 08:10 +0800, Changli Gao wrote:
>> On Wed, Aug 25, 2010 at 8:03 AM, Joe Perches <[email protected]> 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([email protected])