ToT build failure with ToT GCC (strncpy warning)

[Florian Weimer]

On 11/13/2017 05:28 PM, Steve Ellcey wrote:
> 
> A recent change to GCC has caused a glibc build failure.  The GCC
> change was for strncpy buffer overflow checking (PR c/81117 in the GCC
> bugzilla).  The resulting glibc build failure is:
> 
> ../sysdeps/unix/sysv/linux/if_index.c:46:3: error: ‘strncpy’ specified
> bound 16 equals destination size [-Werror=stringop-truncation]
>  Â Â Â strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
>  Â Â Â ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> It looks like GCC ran into this themselves and their fix was to change
> the strncpy call to memcpy.  The glibc breakage is also noted in GCC
> bug bootstrap/82948 but I don't see it mentioned in the glibc mailing
> lsit anywhere.
> 
> Does changing the strncpy call here to memcpy sound like the right fix?

See the existing thread “[PATCH] add attribute nonstring”.

Thanks,
Florian