[PATCH v4] socket: Use may_alias on sockaddr structs (bug 19622)
Carlos O'Donell
carlos@redhat.com
Tue May 14 12:56:42 GMT 2024
On 5/10/24 2:24 AM, Florian Weimer wrote:
> This supports common coding patterns. The GCC C front end before
> version 7 rejects the may_alias attribute on a struct definition
> if it was not present in a previous forward declaration, so this
> attribute can only be conditionally applied.
>
> This implements the spirit of the change in Austin Group issue 1641.
>
> Suggested-by: Marek Polacek <polacek@redhat.com>
> Suggested-by: Jakub Jelinek <jakub@redhat.com>
>
Missing the RB from Same James? It hasn't changed substantially since then.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> ---
> v2: Mention Austing Group issue 1641. Correct the GCC version range.
> The C front end was changed early in the 7 release cycle.
> v3: Require the GCC 7 release version based on feedback from Jakub.
> v4: Fix typo in commit message.
>
> bits/socket.h | 4 ++--
> inet/netinet/in.h | 8 +++++---
> misc/sys/cdefs.h | 9 +++++++++
> socket/sys/un.h | 2 +-
> sysdeps/mach/hurd/bits/socket.h | 4 ++--
> sysdeps/unix/sysv/linux/bits/socket.h | 4 ++--
> sysdeps/unix/sysv/linux/net/if_packet.h | 2 +-
> sysdeps/unix/sysv/linux/netash/ash.h | 2 +-
> sysdeps/unix/sysv/linux/neteconet/ec.h | 2 +-
> sysdeps/unix/sysv/linux/netiucv/iucv.h | 2 +-
> 10 files changed, 25 insertions(+), 14 deletions(-)
>
> diff --git a/bits/socket.h b/bits/socket.h
> index 13de124bac..772074d52a 100644
> --- a/bits/socket.h
> +++ b/bits/socket.h
> @@ -149,7 +149,7 @@ enum __socket_type
> #include <bits/sockaddr.h>
>
> /* Structure describing a generic socket address. */
> -struct sockaddr
> +struct __attribute_struct_may_alias__ sockaddr
> {
> __SOCKADDR_COMMON (sa_); /* Common data: address family and length. */
> char sa_data[14]; /* Address data. */
> @@ -166,7 +166,7 @@ struct sockaddr
> #define _SS_PADSIZE \
> (_SS_SIZE - __SOCKADDR_COMMON_SIZE - sizeof (__ss_aligntype))
>
> -struct sockaddr_storage
> +struct __attribute_struct_may_alias__ sockaddr_storage
> {
> __SOCKADDR_COMMON (ss_); /* Address family, etc. */
> char __ss_padding[_SS_PADSIZE];
> diff --git a/inet/netinet/in.h b/inet/netinet/in.h
> index fa57b61079..f684be5beb 100644
> --- a/inet/netinet/in.h
> +++ b/inet/netinet/in.h
> @@ -244,7 +244,7 @@ extern const struct in6_addr in6addr_loopback; /* ::1 */
>
>
> /* Structure describing an Internet socket address. */
> -struct sockaddr_in
> +struct __attribute_struct_may_alias__ sockaddr_in
> {
> __SOCKADDR_COMMON (sin_);
> in_port_t sin_port; /* Port number. */
> @@ -257,9 +257,11 @@ struct sockaddr_in
> - sizeof (struct in_addr)];
> };
>
> -#if !__USE_KERNEL_IPV6_DEFS
> +#if __USE_KERNEL_IPV6_DEFS
> +struct __attribute_struct_may_alias__ sockaddr_in6;
> +#else
> /* Ditto, for IPv6. */
> -struct sockaddr_in6
> +struct __attribute_struct_may_alias__ sockaddr_in6
> {
> __SOCKADDR_COMMON (sin6_);
> in_port_t sin6_port; /* Transport layer port # */
> diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
> index 2e8279a2c7..ab9620bd0d 100644
> --- a/misc/sys/cdefs.h
> +++ b/misc/sys/cdefs.h
> @@ -874,4 +874,13 @@ _Static_assert (0, "IEEE 128-bits long double requires redirection on this platf
> # define __attribute_returns_twice__ /* Ignore. */
> #endif
>
> +/* Mark struct types as aliasable. Restricted to compilers that
> + support forward declarations of structs in the presence of the
> + attribute. */
> +#if __GNUC_PREREQ (7, 1) || defined __clang__
OK. Resolve's Jakub's suggestion to use 7.1.
> +# define __attribute_struct_may_alias__ __attribute__ ((__may_alias__))
> +#else
> +# define __attribute_struct_may_alias__
> +#endif
> +
> #endif /* sys/cdefs.h */
> diff --git a/socket/sys/un.h b/socket/sys/un.h
> index bf03b7d6ce..ff9cbd6efa 100644
> --- a/socket/sys/un.h
> +++ b/socket/sys/un.h
> @@ -26,7 +26,7 @@
> __BEGIN_DECLS
>
> /* Structure describing the address of an AF_LOCAL (aka AF_UNIX) socket. */
> -struct sockaddr_un
> +struct __attribute_struct_may_alias__ sockaddr_un
> {
> __SOCKADDR_COMMON (sun_);
> char sun_path[108]; /* Path name. */
> diff --git a/sysdeps/mach/hurd/bits/socket.h b/sysdeps/mach/hurd/bits/socket.h
> index 3e72f9fa93..b5eeac3731 100644
> --- a/sysdeps/mach/hurd/bits/socket.h
> +++ b/sysdeps/mach/hurd/bits/socket.h
> @@ -153,7 +153,7 @@ enum __socket_type
> #include <bits/sockaddr.h>
>
> /* Structure describing a generic socket address. */
> -struct sockaddr
> +struct __attribute_struct_may_alias__ sockaddr
> {
> __SOCKADDR_COMMON (sa_); /* Common data: address family and length. */
> char sa_data[14]; /* Address data. */
> @@ -170,7 +170,7 @@ struct sockaddr
> #define _SS_PADSIZE \
> (_SS_SIZE - __SOCKADDR_COMMON_SIZE - sizeof (__ss_aligntype))
>
> -struct sockaddr_storage
> +struct __attribute_struct_may_alias__ sockaddr_storage
> {
> __SOCKADDR_COMMON (ss_); /* Address family, etc. */
> char __ss_padding[_SS_PADSIZE];
> diff --git a/sysdeps/unix/sysv/linux/bits/socket.h b/sysdeps/unix/sysv/linux/bits/socket.h
> index 86444f0018..5ab19a8c08 100644
> --- a/sysdeps/unix/sysv/linux/bits/socket.h
> +++ b/sysdeps/unix/sysv/linux/bits/socket.h
> @@ -181,7 +181,7 @@ typedef __socklen_t socklen_t;
> #include <bits/sockaddr.h>
>
> /* Structure describing a generic socket address. */
> -struct sockaddr
> +struct __attribute_struct_may_alias__ sockaddr
> {
> __SOCKADDR_COMMON (sa_); /* Common data: address family and length. */
> char sa_data[14]; /* Address data. */
> @@ -194,7 +194,7 @@ struct sockaddr
> #define _SS_PADSIZE \
> (_SS_SIZE - __SOCKADDR_COMMON_SIZE - sizeof (__ss_aligntype))
>
> -struct sockaddr_storage
> +struct __attribute_struct_may_alias__ sockaddr_storage
> {
> __SOCKADDR_COMMON (ss_); /* Address family, etc. */
> char __ss_padding[_SS_PADSIZE];
> diff --git a/sysdeps/unix/sysv/linux/net/if_packet.h b/sysdeps/unix/sysv/linux/net/if_packet.h
> index 9ffb69b508..c17e1c23c5 100644
> --- a/sysdeps/unix/sysv/linux/net/if_packet.h
> +++ b/sysdeps/unix/sysv/linux/net/if_packet.h
> @@ -26,7 +26,7 @@
> From Linux 2.1 the AF_PACKET interface is preferred and you should
> consider using it in place of this one. */
>
> -struct sockaddr_pkt
> +struct __attribute_struct_may_alias__ sockaddr_pkt
> {
> __SOCKADDR_COMMON (spkt_);
> unsigned char spkt_device[14];
> diff --git a/sysdeps/unix/sysv/linux/netash/ash.h b/sysdeps/unix/sysv/linux/netash/ash.h
> index 7d885d17cc..7a6ff50b17 100644
> --- a/sysdeps/unix/sysv/linux/netash/ash.h
> +++ b/sysdeps/unix/sysv/linux/netash/ash.h
> @@ -22,7 +22,7 @@
> #include <features.h>
> #include <bits/sockaddr.h>
>
> -struct sockaddr_ash
> +struct __attribute_struct_may_alias__ sockaddr_ash
> {
> __SOCKADDR_COMMON (sash_); /* Common data: address family etc. */
> int sash_ifindex; /* Interface to use. */
> diff --git a/sysdeps/unix/sysv/linux/neteconet/ec.h b/sysdeps/unix/sysv/linux/neteconet/ec.h
> index b07a107961..f3132f06ff 100644
> --- a/sysdeps/unix/sysv/linux/neteconet/ec.h
> +++ b/sysdeps/unix/sysv/linux/neteconet/ec.h
> @@ -28,7 +28,7 @@ struct ec_addr
> unsigned char net; /* Network number. */
> };
>
> -struct sockaddr_ec
> +struct __attribute_struct_may_alias__ sockaddr_ec
> {
> __SOCKADDR_COMMON (sec_);
> unsigned char port; /* Port number. */
> diff --git a/sysdeps/unix/sysv/linux/netiucv/iucv.h b/sysdeps/unix/sysv/linux/netiucv/iucv.h
> index f5fad81751..27151e8bbe 100644
> --- a/sysdeps/unix/sysv/linux/netiucv/iucv.h
> +++ b/sysdeps/unix/sysv/linux/netiucv/iucv.h
> @@ -23,7 +23,7 @@
>
> __BEGIN_DECLS
>
> -struct sockaddr_iucv
> +struct __attribute_struct_may_alias__ sockaddr_iucv
> {
> __SOCKADDR_COMMON (siucv_);
> unsigned short siucv_port; /* Reserved */
>
> base-commit: 143ef68b2aded7c794956beddad495af8c7d3251
>
--
Cheers,
Carlos.
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