From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: Re: Possible file stream bug
Date: Wed, 24 Oct 2012 16:51:31 -0400 [thread overview]
Message-ID: <20121024205130.GI254@brightrain.aerifal.cx> (raw)
In-Reply-To: <CAKHv7pi+hL_EF+GhezqcMgEcmitccxbhnruFgtBs=dADyuAiPg@mail.gmail.com>
On Wed, Oct 24, 2012 at 10:16:01PM +0200, Paul Schutte wrote:
> Hi
>
> While investigating this, I stumbled upon another bug:
>
> #include <unistd.h>
> #include <stdio.h>
>
> int main() {
> FILE *fstream;
> int len;
>
> fclose(stdout);
>
> len=printf("test this\n");
>
> fprintf(stderr,"%d\n",len);
>
> return 0;
> }
>
> Musl's printf gives the amount of bytes no matter whether it succeeds or
> fails.
> It should return a negative value in case of failure.
You invoked undefined behavior by accessing a FILE object after
calling fclose on it. Thus anything can happen. Even if you just
closed the underlying file descriptor #1 without closing the FILE,
printf would be under no obligation to return -1 since the write error
need not be detected until the buffer gets flushed.
Rich
next prev parent reply other threads:[~2012-10-24 20:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-24 19:36 Paul Schutte
2012-10-24 20:16 ` Paul Schutte
2012-10-24 20:51 ` Rich Felker [this message]
2012-10-24 20:59 ` Rich Felker
2012-10-24 21:22 ` Paul Schutte
2012-10-24 21:25 ` Rich Felker
2012-10-24 21:54 ` Paul Schutte
2012-10-24 21:53 ` Rich Felker
2012-10-26 21:57 ` Rich Felker
2012-10-24 21:41 ` Szabolcs Nagy
2012-10-24 21:52 ` Rich Felker
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