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Date: Fri, 26 Sep 2014 03:05:48 -0400
From: Rich Felker <>
	黄建忠 <>
Subject: Re: fdopen/fflush problem

On Fri, Sep 26, 2014 at 08:39:39AM +0200, Szabolcs Nagy wrote:
> * Rich Felker <> [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

    "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

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?


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