Re: fprintf() crashes on wide-oriented stream.

[Jeff Johnston <jjohnstn@redhat.com>]

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I'll look at it.

-- Jeff J.

On Tue, Oct 3, 2023 at 4:30 AM Takashi Yano <takashi.yano@nifty.ne.jp>
wrote:

> Ping?
>
> Is this Corinna's domain?
>
> On Tue, 26 Sep 2023 17:30:13 +0900
> Takashi Yano wrote:
> > On Tue, 26 Sep 2023 12:41:47 +0900
> > Takashi Yano wrote:
> > > Hi,
> > >
> > > I noticed that the following test case crashes at printf() with current
> > > newlib.
> > >
> > >
> > > #include <stdio.h>
> > > #include <wchar.h>
> > > #include <locale.h>
> > >
> > > int main()
> > > {
> > >     setlocale(LC_ALL, "C.UTF-8");
> > >     wprintf(L"%ls\n", L"aaaa"); /* or fwide(stdout, 1); */
> > >     printf("%ls\n", L"bbbb");  /* <--- crash here */
> > >     return 0;
> > > }
> > >
> > >
> > > I looked into this problem and found the cause.
> > >
> > > A narrow char string which can be odd bytes in length is cast into
> > > a wide char string which should be even bytes in length in __sprint_r/
> > > __sfputs_r based on the __SWID flag. As a result, if the length is
> > > odd bytes, the reading buffer runs over the buffer length, which causes
> > > a crash. If the length is even bytes, crash does not happen, but
> garbage
> > > is printed. This hapens if printf("%ls\r\n", L"bbbb"); is used instead.
> > >                                       ^^
> > >
> > > The same issue seemed to be reported ten years ago.
> > > https://sourceware.org/pipermail/newlib/2013/010831.html
> > >
> > > I have built a patch attached for this issue.
> > >
> > > With this patch, __sfputs_r/__sprint_r is split into two versions, one
> > > is for vfprintf which does not handle wide string, and the other (newly
> > > introduced __sfputws_r/__swprin_r) is for vfwprintf which handles wide
> > > string. Please note that fprintf gets working for wide orient stream
> > > just like BSD libc, which behaves differently from GNU libc.
> > >
> > > This patch also fixes nano-vfprintf.c as well as vfprintf.c/vfwprintf.c
> > > in the same manner.
> >
> > v2: Remove __sprint_r from nano-vfprintf.c which does not seem to be used
> >     anymore.
> >
> > --
> > Takashi Yano <takashi.yano@nifty.ne.jp>
>
>
> --
> Takashi Yano <takashi.yano@nifty.ne.jp>
>
>