5 Nov
2018
5 Nov
'18
3:34 a.m.
On Nov 4, 2018, at 4:28 AM, arnold(a)skeeve.com wrote:
Chris Hanson <cmhanson(a)eschatologist.net> wrote:
Every piece of code that wants to call, say, read(2) needs to handle not only real errors
but also needs to special-case EINTR and retry the read. Thus you should virtually never
use read(2), only ever something like this:
ssize_t safe_read(int fd, void *buf, size_t buf_size)
{
ssize_t rc;
do {
rc = read(fd, buf, buf_size);
} while ((rc == -1) && (errno == EINTR));
return rc;
}
And do this for every classic system call, since virtually no client code should ever have
to care about EINTR. It was early an implementation expediency that became API and that
everyone now has to just deal with because you can’t expect the system call interface you
use to do this for you.
This is the sort of wart that should’ve been fixed by System V and/or BSD 4 at latest.
— Chris
If anyone ever asks me about the elegance of
UNIX, there’s one word, or really term, that springs to mind: EINTR.
The fact that man pages on modern systems still describe calls as returning -1 with errno
set to EINTR baffles me.
Can you explain this some more? This sounds like a claim that UNIX
isn't elegant. But I'm not following whatever it is you're saying.