On 31/10/2024 17:41, Bastien Roucariès wrote:
> Hi,
>
> On debian side we will like to avoid use of sigill to detect feature.
>
> https://sources.debian.org/src/postgresql-17/17.0-1/src/port/pg_crc32c_armv8_choose.c/#L55
>
> is really bad.
Why is it bad?
> Could you use the canonical way under linux
>
> #include <sys/auxv.h>
> #include <asm/hwcap.h>
>
> #if defined(__aarch64__)
> return !(getauxval(AT_HWCAP) & HWCAP_CRC32);
> #else
> return !(getauxval(AT_HWCAP2) & HWCAP2_CRC32);
> #endif
We used to do that, but it was changed in commit 1c72ec6f. Looking at
the discussion that led to it, it's not clear to me why we switched [1].
Portablity to non-glibc systems maybe?
If there's a handy, portable way to check CPU capabilities, I agree it
seem less hacky than catching SIGILL...
[1]
https://www.postgresql.org/message-id/CAEepm%3D02Run-Pk3xyt%2BRV3p1N%2B7cKZxN95_MamaJw8Cnw%2BDwjQ%40mail.gmail.com
--
Heikki Linnakangas
Neon (https://neon.tech)
