ToT build failure with ToT GCC (strncpy warning)

[Steve Ellcey]

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]
   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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?

Steve Ellcey
sellcey@cavium.com