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Message-ID: <20140926070548.GR23797@brightrain.aerifal.cx>
Date: Fri, 26 Sep 2014 03:05:48 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com,
黄建忠 <jianzhong.huang@...oft.com.cn>
Subject: Re: fdopen/fflush problem
On Fri, Sep 26, 2014 at 08:39:39AM +0200, Szabolcs Nagy wrote:
> * Rich Felker <dalias@...c.org> [2014-09-26 02:18:10 -0400]:
> > See the following text from the man page:
> >
> > The mkostemp() function is like mkstemp(), with the difference
> > that the following bits???with the same meaning as for open(2)???may
> > be specified in flags: O_APPEND, O_CLOEXEC, and O_SYNC. Note that
> > when creating the file, mkostemp() includes the values O_RDWR,
> > O_CREAT, and O_EXCL in the flags argument given to open(2);
> > including these values in the flags argument given to mkostemp()
> > is unnecessary, and produces errors on some systems.
>
> ah i didnt see this, so it's not a musl bug
I forgot that this function was accepted for inclusion in POSIX, so we
need to check that too. The accepted text is in
http://austingroupbugs.net/view.php?id=411
"The mkostemp( ) function shall be equivalent to the mkstemp( )
function, except that the flag argument may contain additional
flags (from <fcntl.h>) to be used as if by open( ). Behavior is
unspecified if the flag argument contains more than the following
flags:"
The list that follows includes just O_APPEND, O_CLOEXEC, and O_*SYNC,
so including O_WRONLY has unspecified behavior. However, since this is
just unspecified, not undefined, it seems bad for something "horribly
wrong" to happen, like a file with no access like we're getting now.
Indeed, POSIX will define an optional error:
"The mkostemp( ) function may fail if:
[EINVAL] The value of the flag argument is invalid."
So I think we should either make this error be detected, or silently
mask off the bad access mode. My leaning would be towards reporting it
as an error. Opinions?
Rich
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