Re: drivers/hwmon/pmbus/ibm-cffps.c:184:60: warning: '%04X' directive output may be truncated writing between 4 and 8 bytes into a region of size 5

[David Laight]

On Fri, 20 Dec 2024 09:03:51 -0800
Guenter Roeck <linux@xxxxxxxxxxxx> wrote:

> On 12/20/24 08:30, David Laight wrote:
...
> >>  
> >>>      drivers/hwmon/pmbus/ibm-cffps.c:171:60: warning: '%02X' directive output may be truncated writing between 2 and 8 bytes into a region of size 3 [-Wformat-truncation=]
> >>>        171 |                                 snprintf(&data[i * 2], 3, "%02X", rc);  
> > 
> > The only ways I know are to bound check the value or to use
> > OPTIMISER_HIDE_VAR() on the length.
> >   
> 
> -                               snprintf(&data[i * 2], 3, "%02X", rc);
> +                               snprintf(&data[i * 2], 3, "%02X", rc & 0xff);
> 
> works as well, at least with gcc 11 and 12, but I really dislike that kind of nonsense.

Ditto.
Using the result in some ways can also remove the warning.
But you have to try quite hard, a simple (void) really ought to be
enough to show you 'just don't care' but even 'if (snprintf(...)) {}'
isn't enough (it does silence 'warn-unused-result').

I mean, the whole point of snprintf() is that it truncates.

	David