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>
(cherry picked from commit 8d7b6b4cb27d4dec1dd5f7960298c1699275f962)

6 files changed, 8 insertions, 8 deletions

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 0d86feb4ca..6dab283a2e 100644
--- a/sysdeps/unix/sysv/linux/bits/socket.h
+++ b/sysdeps/unix/sysv/linux/bits/socket.h
@@ -180,7 +180,7 @@ 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.  */
@@ -193,7 +193,7 @@ 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 */