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Re: [PATCH] Fix strict-aliasing warning in resolv/res_hconf.c
- From: Pedro Alves <palves at redhat dot com>
- To: sellcey at imgtec dot com, Florian Weimer <fweimer at redhat dot com>
- Cc: Andreas Schwab <schwab at suse dot de>, Roland McGrath <roland at hack dot frob dot com>, Paul Eggert <eggert at cs dot ucla dot edu>, libc-alpha at sourceware dot org
- Date: Wed, 27 May 2015 10:19:38 +0100
- Subject: Re: [PATCH] Fix strict-aliasing warning in resolv/res_hconf.c
- Authentication-results: sourceware.org; auth=none
- References: <5bfa6373-3817-4d31-a5ee-a8676e79b723 at BAMAIL02 dot ba dot imgtec dot org> <555BB55E dot 3050304 at cs dot ucla dot edu> <1432075989 dot 16668 dot 62 dot camel at ubuntu-sellcey> <555BC19B dot 90001 at cs dot ucla dot edu> <1432077972 dot 16668 dot 65 dot camel at ubuntu-sellcey> <20150519235817 dot 9516F2C3A73 at topped-with-meat dot com> <555C3E0B dot 2040404 at redhat dot com> <mvma8wzbqsv dot fsf at hawking dot suse dot de> <555C48F0 dot 2030208 at redhat dot com> <1432139240 dot 16668 dot 77 dot camel at ubuntu-sellcey>
On 05/20/2015 05:27 PM, Steve Ellcey wrote:
> diff --git a/resolv/res_hconf.c b/resolv/res_hconf.c
> index 73942e8..3b05287 100644
> --- a/resolv/res_hconf.c
> +++ b/resolv/res_hconf.c
> @@ -444,13 +444,13 @@ _res_hconf_reorder_addrs (struct hostent *hp)
>
> ifaddrs[new_num_ifs].addrtype = AF_INET;
> ifaddrs[new_num_ifs].u.ipv4.addr =
> - ((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
> + cur_ifr->ifr_addr_in.sin_addr.s_addr;
Without adding a new union member, isn't the simplest to just take a
copy step? The interface already clearly assumes that a sockaddr_in
fits in a sockaddr. Something like:
union
{
struct sockaddr sa;
struct sockaddr_in sin;
} ss;
- ifaddrs[new_num_ifs].u.ipv4.addr =
- ((struct sockaddr_in *) &cur_ifr->ifr_addr)->sin_addr.s_addr;
+ ss.sa = cur_ifr->ifr_addr;
+ ifaddrs[new_num_ifs].u.ipv4.addr = ss.sin.sin_addr.s_addr;
etc. Maybe the compiler even elides the copying. (And if it doesn't,
would it matter here?)
Thanks,
Pedro Alves