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Message-ID: <20171119011433.GH1627@brightrain.aerifal.cx>
Date: Sat, 18 Nov 2017 20:14:33 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] fix fgetwc when decoding a character that crosses
buffer boundary
On Sat, Nov 18, 2017 at 08:12:57PM -0500, Rich Felker wrote:
> On Sat, Nov 18, 2017 at 05:51:48PM +0100, Szabolcs Nagy wrote:
> > Update the buffer position according to the bytes consumed into st when
> > decoding an incomplete character at the end of the buffer.
> > ---
> > src/stdio/fgetwc.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/src/stdio/fgetwc.c b/src/stdio/fgetwc.c
> > index e455cfec..a00c1a86 100644
> > --- a/src/stdio/fgetwc.c
> > +++ b/src/stdio/fgetwc.c
> > @@ -15,20 +15,21 @@ static wint_t __fgetwc_unlocked_internal(FILE *f)
> > if (f->rpos < f->rend) {
> > l = mbrtowc(&wc, (void *)f->rpos, f->rend - f->rpos, &st);
> > if (l+2 >= 2) {
> > f->rpos += l + !l; /* l==0 means 1 byte, null */
> > return wc;
> > }
> > if (l == -1) {
> > f->rpos++;
> > return WEOF;
> > }
> > + f->rpos = f->rend;
> > } else l = -2;
>
> Thanks, applying! Here is a test case that demonstrates the bug
> reproducibly; feel free to adapt (it should probably use the framework
> functions for getting a utf-8 locale and error reporting) & include it
> in libc-test.
>
> Rich
> #include <stdio.h>
> #include <poll.h>
^^^^^^^^
Ooops, this is spurious/leftover from when I thought I was going to
need to do something fancier to reliably trigger it.
> #include <locale.h>
> #include <wchar.h>
> #include <unistd.h>
>
> int main()
> {
> setlocale(LC_CTYPE, "");
> int p[2];
> pipe(p);
> write(p[1], "x\340\240", 3);
> dup2(p[0], 0);
> wchar_t wc;
> wc = fgetwc(stdin);
> write(p[1], "\200", 1);
> close(p[1]);
> wc = fgetwc(stdin);
> printf("got %x\n", wc);
> }
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