Re: [PATCH 2/2] Y2038: make __tz_convert compatible with 64-bit-time

[Albert ARIBAUD <albert.aribaud@3adev.fr>]

Hi Florian,

On Wed, 13 Jun 2018 11:40:04 +0200, Florian Weimer <fweimer@redhat.com>
wrote :

> On 06/13/2018 11:36 AM, Albert ARIBAUD wrote:
> > Hi Florian,
> > 
> > On Wed, 13 Jun 2018 11:10:09 +0200, Florian Weimer <fweimer@redhat.com>
> > wrote :
> >   
> >> On 06/13/2018 09:00 AM, Albert ARIBAUD (3ADEV) wrote:  
>  [...]  
> >>
> >> Functions in the private namespace should be exported as GLIBC_PRIVATE.
> >> Except __gmtime64_r, these functions have unwanted side effects and
> >> cannot really be called from other parts of glibc anyway.  
> > 
> > They're going to be implementations of APIs called from user source code
> > if/when it defines _TIME_BITS equal to 64 (that'll be the last patch in
> > the whole series), so I don't understand how they could be considered
> > GLIBC_PRIVATE.  
> 
> Why do they use the __ prefix?  We generally do not do that.

I believe it stemmed from the fact that source code should not spell
these functions by their explicit name -- that name is to be used by
glibc only. User source code should keep using the historical names
(here, "gmtime_r"); if it has defined _TIME_BITS equal to 64, then the
glibc public headers will alias (or barring that, #define) gmtime_r to
__gmtime64_r (the 64-bit-time implementation); otherwise, "gmtime_r"
will be used as-is (the 32-bit-time implementation).

So to make sure the symbols were considered to not be for (direct)
public use, they have to start with an underscore.

> > As for the side effects, which ones are you thinking of? The ones I am
> > aware of are those already present in the 32-bit-time versions and are
> > "regrettable but established behavior".  
> 
> The side effects simply mean that we cannot call this functions as an 
> internal implementation detail of another function, so there should be 
> no reason for an export in the private namespace (with the __prefix and 
> GLIBC_PRIVATE).

Actually another function can call these functions -- the 32-bit-time
wrappers do that exactly. I must be missing your point.

> Thanks,
> Florian

Cordialement,
Albert ARIBAUD
3ADEV