Re: Can we drop upstream Linux x32 support?

From: Bernd Petrovitsch
Date: Fri Dec 14 2018 - 09:15:09 EST

On 13/12/2018 17:02, Rich Felker wrote:
> On Tue, Dec 11, 2018 at 11:29:14AM +0100, John Paul Adrian Glaubitz wrote:
>> I can't say anything about the syscall interface. However, what I do know
>> is that the weird combination of a 32-bit userland with a 64-bit kernel
>> interface is sometimes causing issues. For example, application code usually
>> expects things like time_t to be 32-bit on a 32-bit system. However, this

IMHO this just historically grown (as in "it has been forever that way"
- it sounds way better in Viennese dialect though;-).

>> isn't the case for x32 which is why code fails to build.
> I don't see any basis for this claim about expecting time_t to be
> 32-bit. I've encountered some programs that "implicitly assume" this
> by virtue of assuming they can cast time_t to long to print it, or
> similar. IIRC this was an issue in busybox at one point; I'm not sure
> if it's been fixed. But any software that runs on non-Linux unices has
> long been corrected. If not, 2038 is sufficiently close that catching
> and correcting any such remaining bugs is more useful than covering
> them up and making the broken code work as expected.

Yup, unconditionally providing 64bit
time_t/timespec/timeval/...-equivalents with libc and syscall support
also for 32bit architectures (and deprecating all 32bit versions) should
be the way to go.

FWIW I have
---- snip ----
#if defined __x86_64__
# if defined __ILP32__ // x32
# define PRI_time_t "lld" // for time_t
# define PRI_nsec_t "lld" // for tv_nsec in struct timespec
# else // x86_64
# define PRI_time_t "ld" // for time_t
# define PRI_nsec_t "ld" // for tv_nsec in struct timespec
# endif
#else // i[3-6]68
# define PRI_time_t "ld" // for time_t
# define PRI_nsec_t "ld" // for tv_nsec in struct timespec
---- snip ----
in my userspace code for printf() and friends - I don't know how libc's
react to such a patch (and I don't care for the name of the macros as
long it's obviously clear for which type they are).
I assume/fear we won't get additional modifiers into the relevant
standards for libc types (as they are far more like pid_t, uid_t etc.).
And casting to u/intmaxptr_t to get a defined printf()-modifier doesn't
look appealing to me to "solve" such issues.

"I dislike type abstraction if it has no real reason. And saving
on typing is not a good reason - if your typing speed is the main
issue when you're coding, you're doing something seriously wrong."
- Linus Torvalds

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