ACK: [PATCH 2/3] fwts_hwinfo.c: fix strict-aliasing error with old gcc

[Alex Hung]

On 2016-11-01 06:07 AM, Erico Nunes wrote:
> When building the current fwts release with an older gcc 4.4, we get the
> following error due to breaking strict-aliasing rules, despite the
> comment in the code which states there has been an attempt to solve this
> in the past:
>
>   fwts_hwinfo.c: In function ‘fwts_hwinfo_get’:
>   fwts_hwinfo.c:420: error: dereferencing pointer ‘sockaddr’ does break
>   strict-aliasing rules
>   fwts_hwinfo.c:419: note: initialized from here
>
> This new attempt to fix it just makes a copy of the whole "buf.ifr_addr"
> to into sockaddr to avoid running into any strict-aliasing problems.
> As there are still supported systems with older gcc versions, such as
> RHEL6, it is interesting to have this fixed.
>
> This has been built and tested with gcc 6.2.1, gcc 4.8.5 and gcc 4.4.7.
>
> Signed-off-by: Erico Nunes <ernunes at redhat.com>
> ---
>  src/lib/src/fwts_hwinfo.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/src/lib/src/fwts_hwinfo.c b/src/lib/src/fwts_hwinfo.c
> index 083b94d..d749cf2 100644
> --- a/src/lib/src/fwts_hwinfo.c
> +++ b/src/lib/src/fwts_hwinfo.c
> @@ -381,7 +381,7 @@ static int fwts_hwinfo_net_get(
>
>  	while ((d = readdir(dp)) != NULL) {
>  		struct ifreq buf;
> -		struct sockaddr_in *sockaddr;
> +		struct sockaddr_in sockaddr;
>  		fwts_net_config *net_config;
>
>  		if (d->d_name[0] == '.')
> @@ -416,8 +416,8 @@ static int fwts_hwinfo_net_get(
>  				fwts_log_error(fw, "Cannot get address for device %s.", d->d_name);
>  		}
>  		/* GCC 4.4 is rather overly pedantic in strict aliasing warnings, this avoids it */
> -		sockaddr = (struct sockaddr_in *)&buf.ifr_addr;
> -		net_config->addr = strdup(inet_ntoa((struct in_addr)sockaddr->sin_addr));
> +		memcpy(&sockaddr, &buf.ifr_addr, sizeof(sockaddr));
> +		net_config->addr = strdup(inet_ntoa((struct in_addr)sockaddr.sin_addr));
>  		if (net_config->addr == NULL) {
>  			fwts_log_error(fw, "Cannot allocate net config H/W address.");
>  			fwts_hwinfo_net_free(net_config);
>


Acked-by: Alex Hung <alex.hung at canonical.com>