Re: time64 / Large File Support: 2) default time64 breaks legacy 32bit binaries

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 26/01/23 23:38, Paul Eggert wrote:
> On 1/26/23 05:21, Adhemerval Zanella Netto via Libc-alpha wrote:
>> So although I am not quite against --enable-hard-sys-types64, I personally
>> think we should do something more drastically (which not all other glibc
>> developers agree) and flip the switch to enable 64-bit time_t *as default*
>> and document 32-bit is opt-in.
> 
> Just to clarify, there are two issues here:
> 
> A. Should _FILE_OFFSET_BITS and _TIME_BITS default to 64 instead of to 32?

That is my understanding to make 64-bit time_t the default ABI.

> 
> B. Should _FILE_OFFSET_BITS=64 and _TIME_BITS=64 be the *only* values supported? That is, should the old API (with 32-bit time_t, off_t, etc.) be available only to old 32-bit executables, and not to newly-built 32-bit executables?

That's a good question and I think it does make sense to move the non-LFS
and 32-bit time_t API to compat code and only provide 64-bif off_t/time_t 
support.

> 
> As I understood it, the proposal was that (A) and (B) both default to "no", but '.../configure --enable-hard-sys-types64' would change both (A) and (B) to "yes".
> 
> It sounds like you're proposing a more drastic approach, in which (A) and (B) both default to "yes", but '.../configure --disable-hard-sys-types64' changes them both to "no". Is that right?

Not really, my proposal was initial to set (A) to 'yes' but still allow new
programs to be built with -D_FILE_OFFSET_BITS=32 and -D_TIME_BITS=32.  But
making the later compat symbols seems also a good thing to cement for good
the old interfaces.

I am really trying to avoid a configure switch (such as --disable-hard-sys-types64),
they tend to be become rotten and fail due lack of testing (and also add some
fragmentation due each distro using different switch).

> 
> Another possibility is to adopt the milder approach for glibc version N, and switch to the more drastic approach in glibc version N+1.This would give distros time to test this new configure-time option before it's the default.
Do you mean add the --enable-hard-sys-types64 on glibc N, and then remove it on
N+1 and make the 64-bit the default?