On 03/27/2015 11:20 AM, walter harms wrote:
>
> hi Zhen Ren,
> i tried to create a more simple example. Do you think this is more
> helpful for you ?
Walter,
Your version seems better. See comments below.
> re,
> wh
>
> char *
> make_message2 (const char *fmt, ...)
> {
> int n,size = 0;
> char *p = NULL;
> va_list ap;
>
> /* figure our required size */
> va_start (ap, fmt);
> size = vsnprintf (p, size, fmt, ap);
> va_end (ap);
>
> if (size < 0)
> return NULL;
>
> /* leave room for \0 */
> size++;
> p = malloc (size);
> if (p == NULL)
> return NULL;
>
> va_start (ap, fmt);
> n = vsnprintf (p, size, fmt, ap);
What's missing here is a check on the return value from
the vsnprintf() call. I added one.
I've put your code into the page, replacing the existing
example, with the fix noted above.
Thanks,
Michael
> va_end (ap);
>
> return p;
> }
> Am 27.03.2015 10:52, schrieb Zhen Ren:
>> Hi Michael,
>>
>> I'm so sorry for this negative report.
>>
>> Yeah, you're right. It'll fall through,loop again,do "vsprintf" and return if done.
>>
>> --
>> Best regards,
>> Eric, Ren
>> HA team, SUSE
>>
>>
>>>>>
>>> Hello Zhen Ren,
>>>
>>> On 27 March 2015 at 06:27, Zhen Ren <zren@xxxxxxxx> wrote:
>>>> Hi,
>>>> There is simple bug in EXAMPLE section of "man 3 vsprintf".
>>>>
>>>> Function will return nothing if it steps into the last "else {}".
>>>>
>>>> ------------------ example code -----------------
>>>> char *
>>>> make_message(const char *fmt, ...)
>>>> {
>>>> int n;
>>>> int size = 100; /* Guess we need no more than 100 bytes */
>>>> char *p, *np;
>>>> va_list ap;
>>>> .
>>>> .cut off
>>>> .
>>>> np = realloc(p, size);
>>>> if (np == NULL) {
>>>> free(p);
>>>> return NULL;
>>>> } else {
>>>> p = np;
>>>> + return p;
>>>> }
>>>> }
>>>> }
>>>
>>> I have not looked too closely at the code, but the above report
>>> appears incorrect to me. The function should NOT be returning at that
>>> point. It should be falling through and then round the loop once more.
>>> If I've missed something, could you elaborate a little more on the
>>> problem, please?
>>>
>>> Cheers,
>>>
>>> Michael
>>>
>>>
>>
>>
>> --
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--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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