More on restrict keyword.

[Francis Moreau]

Hello,

I read the latest post on 'restrict' keyword the subject and it makes
me think about the following declaration used by the BSD socket
library:

typedef union {
struct sockaddr * restrict __sockaddr__;
struct sockaddr_at * restrict __sockaddr_at__;
struct sockaddr_un * restrict __sockaddr_un__;
struct sockaddr_in * restrict __sockaddr_in__;
struct sockaddr_in6 * restrict __sockaddr_in6__;
} __SOCKADDR_ARG __attribute__ ((__transparent_union__));

__SOCKADDR_ARG being used as parameter type passed to a couple of
functions such as bind().

Does anybody understand the use of 'restrict' keyword in that case ?

BTW could anybody point out a link that correctly sum up the
definition of 'restrict' ? The formal definition given by the C spec
is almost unreadable for my poor english.

Thanks

 

[Francis Moreau]

I think it means that no two-pointers point to the same thing.
i.e. every pointer points to a unique and seperate struct.

Yes but since the pointers are part of a union object, all pointers are
always aliasing the same objects. So it seems to me that the 'restrict'
keyword is not appropriate here.

http://en.wikipedia.org/wiki/Restrict

Why isn't the spec simple as this ?