Re: System calls parameter restrictions

On 28 Oct 2006 05:03:19 -0700 David Schwartz <davids@xxxxxxxxxxxxx> wrote:
|
| phil-news-nospam@xxxxxxxx wrote:
|
|> Structs small enough to fit in available register space could be passed
|> in much the same way many archtectures do pass values. It's just a big
|> complex value. What if you were passing a 64 bit integer by value, on a
|> 32 bit machine, knowing that there is really no true value as cuh, but
|> only a joining of a pair of 32 bit integers? It really doesn't matter.
|> It can be dealt with one way or another. It can be loaded into a register
|> or a copy can be made through use of pass by reference (pointer). It's
|> just a matter of how the kernel syscall interface is designed and to the
|> extent such a design depends on it, the ABI.
|
| But that would mean that changing a structure would break the ABI. That
| doesn't sound like it's worth it. Think about structures of unknown
| length, such as 'struct sockaddr'. (How do you tell the compiler a
| structure has unknown length?)

Are you saying change the way a struct is passed? Or changing the value
in a struct?

The compiler can pass structs by value. But I think that is only for
structs with a fixed size.

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2006-10-28-1751@xxxxxxxx |
|------------------------------------/-------------------------------------|
.

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