[PATCH v3] libio: do not unbuffer legacy standard files in compatibility mode [BZ #24228]

[Florian Weimer]

* Dmitry V. Levin:

> On Wed, Mar 13, 2019 at 04:08:16PM +0100, Florian Weimer wrote:
>> * Dmitry V. Levin:
>> 
>> > Commit glibc-2.23~693 (a601b74d31ca086de38441d316a3dee24c866305)
>> 
>> Please quote the commit hash and commit subject, kernel-style.
>
> The kernel-style reference would look this way:
>
> Commit a601b74d31ca ("In preparation for fixing BZ#16734, fix failure in
> misc/tst-error1-mem when _G_HAVE_MMAP is turned off.")
>
> I'd like to add a reference to glibc-2.23~693 somewhere because
> I find it useful, but I don't see any suitable place for it
> in this long kernel-style form.

Hmm.  It's not strictly speaking unique because we do not reject
branches, unfortunately.

>> (How did you determine this reference, anyway?)
>
> Sorry?

glibc-2.23~693 looks nice, but I can't get “git describe” to produce.

>> > diff --git a/libio/genops.c b/libio/genops.c
>> > index 2a0d9b81df..aa92d61b6b 100644
>> > --- a/libio/genops.c
>> > +++ b/libio/genops.c
>> > @@ -789,6 +789,10 @@ _IO_unbuffer_all (void)
>> >  
>> >    for (fp = (FILE *) _IO_list_all; fp; fp = fp->_chain)
>> >      {
>> > +#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
>> > +      if (__glibc_unlikely (&_IO_stdin_used == NULL) && _IO_legacy_file (fp))
>> > +	continue;
>> > +#endif
>> 
>> I wonder if we should check _IO_legacy_file only here.  This is related
>> to the previous discussion.
>
> If we omitted the check for _IO_stdin_used, then standard files
> would be skipped and misc/tst-error1-mem would complain.

Really?  Why would _IO_legacy_file be true for those?  That's definitely
not what I intended.

Thanks,
Florian