[chbot] snprintf

[Robin Gilks]

Absolutely correct
As I quoted previously from the man page

*The functions snprintf() and vsnprintf() write at most size bytes
(including the terminating null byte ('\0')) to str.*Note there is no
qualification of what 'size' is referring to, only that it is a restriction
of what is written, nothing to indicate that it's the length of str.
That's the whole problem - sloppy specifications!

I have a standard question I always ask of people who are specifying
anything: "what colour should it be?"
This avoids the exclamation from the developer one day before delivery of:
"colour, colour - nobody told us it had to have a colour!!"


On Tue, Jul 30, 2024 at 10:00 PM Bevin Brett <bevin_brett at hotmail.com>
wrote:

> Getting rid of the struct and the indexing, what you have is
>
>     char ssid[30];
>     char buf[100]
>
>     snprintf (buf, sizeof (ssid), "SSID %s\n", ssid);
>
> which is a request to write 5 chars ("SSID ") followed by any number of
> chars ending in a NUL  (perhaps overrunning the end of ssid if there are no
> NUL in it) followed by \n and a trailing NUL into the first upto 30
> characters of buf.      The warning is assuming (incorrectly) that ssid
> will contain less than 30 non-NULL characters, hence decides may need upto
> 37 characters (should have been 36) (5 + 29 + 1 + 1) and you have only
> supplied 30
>
> /Bevin
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