POSIXfy readlink() call

[Kostik Belousov]

On Mon, May 11, 2009 at 02:46:14PM -0400, John Baldwin wrote:
> On Monday 11 May 2009 2:33:09 pm Kostik Belousov wrote:
> > On Mon, May 11, 2009 at 02:05:07PM -0400, John Baldwin wrote:
> > > On Friday 28 September 2007 10:39:56 pm Ighighi wrote:
> >                         ^^^^^
> 
> Yes, I had this stuck in the back of my head from when it first appeared.
> 
> > > > The POXIX prototype for readlink(2) is:
> > > > ssize_t readlink(const char *restrict path, char *restrict buf, size_t 
> > > > bufsize);
> > > 
> > > It can't simply be corrected as it would change the ABI and thus requires 
> a 
> > > new system call, etc.  However, do you really expect a symlink to be 
> longer 
> > > than 2^31 on a 64-bit machine?
> > 
> > Yes, I agree that this is ABI change.
> > 
> > Meantime,
> > r176215 | ru | 2008-02-12 22:09:04 +0200 (Tue, 12 Feb 2008) | 5 lines
> > 
> > Change readlink(2)'s return type and type of the last argument
> > to match POSIX.
> > 
> > Prodded by:     Alexey Lyashkov
> > 
> > I tried to convince ru@ that ABI breakage is not good, but has not
> > succeeded.
> 
> Ugh, is this only in HEAD?  If so, I will back it out for 8.0.  If this made 
> it into a release then this is a far bigger mess.  Oh, good, this is only in 
> 8.  I will fix this ASAP.  I can just add the new syscall I guess.

You need to symver the syscalls. It requires some ugly games with our
syscall stubs, because gnu ld only honor .symver in the same object where
the symbol is defined. I did prototyped this some time ago, by including
a file with appropriate .symver from all stubs.
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