When using %*s, sscanf should honor conversion specifiers immediately following
the %*s. For example, the following code should find the position of the end of
the string "hello".
int end;
char buf[] = "hello world";
sscanf(buf, "%*s%n", &end);
printf("%d\n", end);
Ideally, sscanf would advance the fmt and str pointers the same as it would
without the *, but the code for that is rather complicated and is not included
in the patch.
Please CC me in replies.
Signed-off-by: Andy Spencer <[email protected]>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 73a14b8..da2daf2 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1766,7 +1766,7 @@ int vsscanf(const char * buf, const char * fmt, va_list args)
* advance both strings to next white space
*/
if (*fmt == '*') {
- while (!isspace(*fmt) && *fmt)
+ while (!isspace(*fmt) && *fmt != '%' && *fmt)
fmt++;
while (!isspace(*str) && *str)
str++;
On Fri, Sep 25, 2009 at 2:27 PM, Andy Spencer <[email protected]> wrote:
> When using %*s, sscanf should honor conversion specifiers immediately following
> the %*s. For example, the following code should find the position of the end of
> the string "hello".
>
> int end;
> char buf[] = "hello world";
> sscanf(buf, "%*s%n", &end);
> printf("%d\n", end);
>
> Ideally, sscanf would advance the fmt and str pointers the same as it would
> without the *, but the code for that is rather complicated and is not included
> in the patch.
Yeah, seems reasonable. So, without your patch, sscanf() in kernel
will ignore everything after '*', right?
>
> Please CC me in replies.
>
>
> Signed-off-by: Andy Spencer <[email protected]>
Fortunately, a quick grep shows no one uses '%*' in sscanf()
in kernel space:
% grep 'sscanf(.*\".*%\*.*\".*)' -nr ./
For completeness,
Acked-by: WANG Cong <[email protected]>
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 73a14b8..da2daf2 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1766,7 +1766,7 @@ int vsscanf(const char * buf, const char * fmt, va_list args)
> * advance both strings to next white space
> */
> if (*fmt == '*') {
> - while (!isspace(*fmt) && *fmt)
> + while (!isspace(*fmt) && *fmt != '%' && *fmt)
> fmt++;
> while (!isspace(*str) && *str)
> str++;
>
> > int end;
> > char buf[] = "hello world";
> > sscanf(buf, "%*s%n", &end);
> > printf("%d\n", end);
>
> Yeah, seems reasonable. So, without your patch, sscanf() in kernel
> will ignore everything after '*', right?
Currently it ignores everything between '*' and whitespace. So '%*s%n'
does not work, but '%*s %n' will correctly return the start of "world".