6 Oct
2024
6 Oct
'24
4:23 a.m.
Rich Salz wrote in
<CAFH29tptJ87d9LbR3DUj1meCaRKn8J6eY0GtBF51xGMnRbkp9w(a)mail.gmail.com>:
|Someone is trying to write something interesting about awk every day of
|this month. The thread starts here:
|https://mastodon.mit.edu/@eichin/113240121988228925
The good thing is that find(1) now has + standardized. Ie his
find /tmp --print0 | xargs -0 stat --format "%s %n"
can now be
find /tmp -exec stat --format "%s %n" {} +
And the POSIX core developers mention (APPLICATION USAGE)
It should be noted that using find with −print0 to pipe input to
xargs −r0 is less safe than using find with −exec because if
find −print0 is terminated after it has written a partial
pathname, the partial pathname may be processed as if it was
a complete pathname.
Heh!
Other than that, off-topic to this thread i am afraid, but should
be posted to another, .. but now that i am here, you know, we all
owe thanks to Geoff Clare and Andrey Josey (and Eric Blake of
RedHat, but really, the Linux approach to this problem makes me
sick, it really should have to work as shown in RFC 2553->3493),
as only thanks to these people the BSD socket API is still
compatible with ISO C .. at least on POSIX systems!
And here is how:
In stating these field mapping requirements when a cast operator
is applied to the various socket address structures, the
standard defines the behavior in circumstances where the
behavior is undefined in the ISO C standard. The onus is on
implementations to ensure that these mappings are as described
in the standard, making use of implementation-specific
extensions if necessary, even though this is not stated
explicitly.
and the solution is
On page 386 line 13115 section <sys/socket.h> DESCRIPTION, change:
When a pointer to a sockaddr_storage structure is cast as
a pointer to a sockaddr structure, the ss_family field of
the sockaddr_storage structure shall map onto the sa_family
field of the sockaddr structure. When a pointer to
a sockaddr_storage structure is cast as a pointer to
a protocol-specific address structure, the ss_family field
shall map onto a field of that structure that is of type
sa_family_t and that identifies the protocol’s address
family.
to:
When a pointer to a sockaddr_storage structure is cast as
a pointer to a sockaddr structure, or vice versa, the
ss_family field of the sockaddr_storage structure shall map
onto the sa_family field of the sockaddr structure. When
a pointer to a sockaddr_storage structure is cast as
a pointer to a protocol-specific address structure, or vice
versa, the ss_family field shall map onto a field of that
structure that is of type sa_family_t and that identifies
the protocol’s address family. When a pointer to a sockaddr
structure is cast as a pointer to a protocol-specific
address structure, or vice versa, the sa_family field shall
map onto a field of that structure that is of type
sa_family_t and that identifies the protocol’s address
family. Additionally, the structures shall be defined in
such a way that the compiler treats an access to the stored
value of the sa_family_t member of any of these structures,
via an lvalue expression whose type involves any other one
of these structures, as permissible, despite the more
restrictive expression rules on stored value access as
stated in the ISO C standard.
as well as this RATIONALE addition:
Note that defining the sockaddr_storage and sockaddr structures
using only mechanisms defined in early editions of the ISO
C standard may produce aliasing diagnostics when applications
use casting between pointers to the various socket address
structures. Because of the large body of existing code utilizing
sockets in a way that could trigger undefined behavior due to
strict aliasing rules, this standard mandates that these
structures can alias each other for accessing the sa_family_t
member of the structures, so as to preserve well-defined
semantics. An implementation's header files may need to use
anonymous unions, or even an implementation-specific extension,
to comply with the requirements of this standard.
I love this standard.
--steffen
|
|Der Kragenbaer, The moon bear,
|der holt sich munter he cheerfully and one by one
|einen nach dem anderen runter wa.ks himself off
|(By Robert Gernhardt)