I read `Advanced Programming in the UNIX Environment, 2nd ed.'. In
section 16.3.2, the book says that variables type struct sockaddr_in;
and/or struct sockaddr_in6; will be cast explicitly to variables type
struct sockaddr; Is this safe? Or will these casts between different
structs result in object slices? see casts at line 6 & 9 for example:
struct sockaddr add1, *add2; /*see struct declarations below*/
struct sockaddr_in add_in;
struct sockaddr_in6 add_in6;
void *p;
add1 = (struct sockaddr) add_in; /*LINE 6*/
p = &add_in6;
add2 = p; /*LINE 9*/
/*add2 = (struct sockaddr*) (p);*/
/*************** *************** ************/
struct sockaddr{
sa_family_t sa_family; /*address family*/
char sa_data[14]; /*variable-length address*/
};
struct sockaddr_in{
sa_family_t sin_family; /*address family*/
in_port sin_port; /*port number*/
struct in_addr {
in_addr_t s_addr;
} sin_addr; /*IPv4 address*/
};
struct sockaddr_in6{
sa_family_t sin6_family; /*address family*/
in_port sin6_port; /*port number*/
uint32_t sin6_flowinfo; /*traffic class and flow
info*/
struct in6_addr {
uint8_t s_addr[16];
} sin6_addr; /*IPv6 address*/
uint32_t sin6_scope_id; /*set of interface for
scope*/
}; 2 7787
lovecreatesbea. ..@gmail.com wrote On 04/04/07 10:50,:
I read `Advanced Programming in the UNIX Environment, 2nd ed.'. In
section 16.3.2, the book says that variables type struct sockaddr_in;
and/or struct sockaddr_in6; will be cast explicitly to variables type
struct sockaddr; Is this safe? Or will these casts between different
structs result in object slices? see casts at line 6 & 9 for example:
struct sockaddr add1, *add2; /*see struct declarations below*/
struct sockaddr_in add_in;
struct sockaddr_in6 add_in6;
void *p;
add1 = (struct sockaddr) add_in; /*LINE 6*/
[...]
Are you sure you have reproduced the code accurately?
A conforming C compiler is required to emit a diagnostic
for your "LINE 6," which I suspect is missing a few
asterisks and ampersands. Please try again, or confirm
that the code you've posted is accurate (in which case,
it isn't C).
-- Er*********@sun .com
On 4 Apr 2007 07:50:38 -0700, "lovecreatesbea ...@gmail.com"
<lo************ ***@gmail.comwr ote:
I read `Advanced Programming in the UNIX Environment, 2nd ed.'. In
section 16.3.2, the book says that variables type struct sockaddr_in;
and/or struct sockaddr_in6; will be cast explicitly to variables type
struct sockaddr; Is this safe? Or will these casts between different
structs result in object slices? see casts at line 6 & 9 for example:
You can't cast struct types in C; if you could, slicing might indeed
be a problem. What you do with the various sockaddr_ structures is
cast _pointers to them_, and where relevant also keep track of the
length explicitly e.g. in the third argument to accept(). This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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