socket: Use may_alias on sockaddr structs (bug 19622)

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>
Reviewed-by: Sam James <sam@gentoo.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

diff --git a/bits/socket.h b/bits/socket.h
index 13de124bac67c21769026d62091154c292360dea..772074d52ab957dfa40ff9921d9d07b35aa41fd5 100644 (file)
--- 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 fa57b6107908590c55d8ee54ccd9f445049f056a..f684be5beb26fc6221d78b4a01ff599648d0b853 100644 (file)
--- 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 2e8279a2c794eec268886190c95bbfd8f7701272..ab9620bd0de05b5f2753d12ddbb37d5ecf28b499 100644 (file)
--- 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__
+# 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 bf03b7d6ce9590656d99ab2ab18ac89d466af8c2..ff9cbd6efa7693d56ae89067900b9363c5a534cf 100644 (file)
--- 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 3e72f9fa93add8885fed347d8f37b25be1541a0a..b5eeac373111e69473086806295fbe393b2ed4c2 100644 (file)
--- 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 86444f0018b0d3da6d20e2d9afc337df9de45b44..5ab19a8c08bf10512f2fb144fcc9d79222022d75 100644 (file)
--- 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 9ffb69b508cc8ca70dd3379e423df2d87a8aaee2..c17e1c23c5cf9169abe2f953df18d2a288d3f59d 100644 (file)
--- 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 7d885d17cc9ec313c12f8520fdb495e8b60ab168..7a6ff50b17b370c480eff68c0a006bd688d4d06d 100644 (file)
--- 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 b07a10796196e28e966026b2604dda94b82f793e..f3132f06ff9f8dee5ad50736fc206f66fddceb78 100644 (file)
--- 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 f5fad817513f3c46cfb5c8b292ed7361ea2f6ec0..27151e8bbe1e7fa256a1e54383cdad562a516cc4 100644 (file)
--- 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 */