helper/ioutil: silence gcc-8 on strncpy 31/5631/3
authorAntonio Borneo <>
Mon, 27 Apr 2020 21:19:14 +0000 (23:19 +0200)
committerAntonio Borneo <>
Sat, 9 May 2020 13:36:56 +0000 (14:36 +0100)
Starting from version 8, gcc issues a warning if strncpy could be
able to truncate a string (so without adding the zero-termination
char in destination) by copying exactly "size" char from a source
string not shorter than "size".
Such truncation from strncpy could actually be the desired code
behaviour, but the way to silent gcc only locally (without global
disabling with -Wno-stringop-truncation) through pragma has other
side effects on portability.

In current code, the source string is always "eth0", because has
been checked right above. So this is a false positive from gcc,
being always strlen("eth0") < 16, the sizeof(ifreq.ifr_name).

Silent gcc by decrementing the "size" and remove:
error: ‘strncpy’ specified bound 16 equals destination
size [-Werror=stringop-truncation]

This file is only optionally compiled together with ZY1000 driver
with --enable-zy1000 --enable-ioutil. This combination is not
checked in jenkins, so the error passed unnoticed.
Plus, the configure flags above are both deprecated!

Change-Id: I229e66227cfd3513139feeaffa47a6e1ec00767b
Signed-off-by: Antonio Borneo <>
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <>

index d4f39e2..c103ce1 100644 (file)
@@ -403,7 +403,7 @@ static int ioutil_Jim_Command_mac(Jim_Interp *interp, int argc,
                        if (strcmp("eth0", ifr->ifr_name) != 0)
                        if (strcmp("eth0", ifr->ifr_name) != 0)
-                       strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name));
+                       strncpy(ifreq.ifr_name, ifr->ifr_name, sizeof(ifreq.ifr_name) - 1);
                        if (ioctl(SockFD, SIOCGIFHWADDR, &ifreq) < 0) {
                                return JIM_ERR;
                        if (ioctl(SockFD, SIOCGIFHWADDR, &ifreq) < 0) {
                                return JIM_ERR;