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

[Joe Perches <joe@perches.com>]

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);