Re: [PATCH v2 1/2] Y2038: make __mktime_internal compatible with __time64_t

[Lukasz Majewski <lukma at denx dot de>]

Hi Paul,

> On 3/29/19 7:24 AM, Lukasz Majewski wrote:
> > With __timespec64 exported (installed in usr/include/*) - there
> > would be an explicit type to show that we are Y2038 safe (when e.g.
> > debugging).  
> 
> That's not much of an argument for exporting __timespec64 to user
> code. When debugging a module, a developer can easily determine
> whether whether time_t is 32- or 64-bit by printing sizeof (time_t)
> in GDB, so the visibility of __timespec64 wouldn't give them any
> information that they don't already have.

Yes, indeed. From practical point of view it would be best to avoid
introducing any new types.

> 
> > I do have a setup where only for glibc compilation I do disable
> > -D_TIME_BITS64, but for _all_ other source code it is enabled.  
> 
> Sorry, I'm not following what you mean by "disable -DTIME_BITS64". Do
> you mean that you compile applications with -D_TIME_BITS=64 and
> compile glibc without it?

Yes, exactly.

That was the case when I last time was trying to use/compile the glibc
being Y2038 safe and as the only libc on the OE/Yocto created system.

However, it was some time ago (before I did some cleanup)
The meta-y2038 relevant branch (but it is outdated now a bit):
https://github.com/lmajewski/meta-y2038/commits/y2038-glibc2.29-deploy

> 
> Does -D_TIME_BITS=64 affect building the GNU C library itself, and if
> so, why? 

I did not checked it with the new code, but yes the glibc was not
buildable with -D_TIME_BITS=64

> (Of course -D_TIME_BITS=64 will affect glibc's auxiliary
> programs like zdump, but these are exceptional cases; I'm worried
> about the library proper.) I thought _TIME_BITS was intended for use
> in user programs, not for use in glibc itself.

Yes, exactly. The _TIME_BITS shall be only supported when building user
programs. Glibc shall not be build with it.

> 
> The answers to the above questions should be documented in
> manual/maint.texi; could you add that to your list of things to do?
> 

Yes, noted.


Best regards,

Lukasz Majewski

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