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Message-ID: <20121116190121.GQ20323@brightrain.aerifal.cx>
Date: Fri, 16 Nov 2012 14:01:21 -0500
From: Rich Felker <dalias@...ifal.cx>
To: musl@...ts.openwall.com
Subject: Re: src/stdio/__stdio_read.c
On Fri, Nov 16, 2012 at 10:29:36AM +0100, Szabolcs Nagy wrote:
> * Yuri Kozlov <yuray@...yakino.ru> [2012-11-16 11:40:57 +0400]:
> > size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
> > {
> > ssize_t cnt;
> > ...
> > cnt = syscall(SYS_readv, ...)
> >
> > if (cnt <= 0) {
> > f->flags |= F_EOF ^ ((F_ERR^F_EOF) & cnt);
> > f->rpos = f->rend = 0;
> > return cnt;
> > }
> > ...
> > }
> >
> > It not raise a problem when a signed value return as unsigned?
> >
>
> no, cnt is either 0 or -1 there (assuming readv works)
>
> this is how __stdio_read is used (f->read):
>
> for (; l; l-=k, dest+=k) {
> k = __toread(f) ? 0 : f->read(f, dest, l);
> if (k+1<=1) {
> FUNLOCK(f);
> return (len-l)/size;
> }
> }
>
> it handles the k == -1 and k == 0 case
As far as I can tell, it would work just fine to have the f->read
function simply return 0 on both EOF and error; there do not seem to
be any callers that care to distinguish these cases. When I get around
to documenting stdio internals I might clean up some things like this.
Rich
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