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Date: Sat, 08 Feb 2020 22:16:00 -0000
From: Lukasz Majewski <lukma@denx.de>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>, Joseph Myers
 <joseph@codesourcery.com>
Cc: Paul Eggert <eggert@cs.ucla.edu>, Alistair Francis
 <alistair23@gmail.com>, Alistair Francis <alistair.francis@wdc.com>, GNU C
 Library <libc-alpha@sourceware.org>, Siddhesh Poyarekar
 <siddhesh@gotplt.org>, Florian Weimer <fweimer@redhat.com>, Florian Weimer
 <fw@deneb.enyo.de>, Zack Weinberg <zackw@panix.com>, Carlos O'Donell
 <carlos@redhat.com>, Andreas Schwab <schwab@suse.de>
Subject: Re: [PATCH v3 7/7] y2038: linux: Provide ___gettimeofday64
 implementation
Message-ID: <20200208231545.038af74a@jawa>
In-Reply-To: <20200205010552.6f0bac91@jawa>
References: <20200129125914.11221-1-lukma@denx.de>
	<20200129125914.11221-7-lukma@denx.de>
	<1bfd0cce-e889-7fce-fe7b-d565ca1a1806@linaro.org>
	<20200205010552.6f0bac91@jawa>
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Hi Adhemerval,

> > >  #else /* USE_IFUNC_GETTIMEOFDAY  */
> > > -# include <time/gettimeofday.c>
> > > +/* Conversion of gettimeofday function to support 64 bit time on
> > > archs
> > > +   with __WORDSIZE =3D=3D 32 and __TIMESIZE =3D=3D 32/64  */
> > > +#include <errno.h>
> > > +
> > > +int
> > > +___gettimeofday64 (struct __timeval64 *restrict tv, void
> > > *restrict tz) +{
> > > +  if (__glibc_unlikely (tz !=3D 0))
> > > +    memset (tz, 0, sizeof (struct timezone));
> > > +
> > > +  struct __timespec64 ts64;
> > > +  int ret =3D __clock_gettime64 (CLOCK_REALTIME, &ts64);
> > > +
> > > +  if (ret =3D=3D 0 && tv)
> > > +    *tv =3D timespec64_to_timeval64 (ts64);=20=20=20=20
> >=20
> > No implicit checks.  Also, we already set 'tv' with nonull
> > attribute, so I am not sure if it is worth to add an extra check
> > for 'tv' validity (specially because users tend to expect low
> > latency for the symbol).
> >=20
> > In any case, if the idea is to add such check as QoI I think it
> > would be better to do a early bail before actually issue
> > __clock_gettime64.=20=20
>=20
> No, this was just my mistake. There was a discussion with Paul and
> Joseph earlier. We shall _only_ check for NULL when it is required by
> syscalls/command documentation. This is the case for e.g. setitimer's
> *old_value pointer.

I've double check this and in the documentation/manual [1] for
gettimeofday there is a sentence:

----8<--------
If either tv or tz is NULL, the corresponding structure is not set or
returned. (However, compilation warnings will result if tv is NULL.)=20
---->8--------

That was the rationale to add the check
if (ret =3D=3D 0 && tv)


I also think that the code as is now is correct - it returns the result
of getting the time from Linux, but it is not updating the tv structure.


Links:

[1] - https://linux.die.net/man/2/gettimeofday


Best regards,

Lukasz Majewski

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