Re: [PATCH] linux: fix ntp_gettime abi break

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

On 03/03/23 13:43, Kacper Piwiński wrote:
> From 64bbb7cc698c8e2c8d8c94247e0bc47ac3b18f77 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?Kacper=20Piwi=C5=84ski?= <vfjpl1@gmail.com>
> Date: Wed, 22 Feb 2023 18:58:38 +0100
> Subject: [PATCH] linux: fix ntp_gettime abi break
> 
> ---
>  sysdeps/unix/sysv/linux/ntp_gettime.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/ntp_gettime.c
> b/sysdeps/unix/sysv/linux/ntp_gettime.c
> index 4879573530..a577314636 100644
> --- a/sysdeps/unix/sysv/linux/ntp_gettime.c
> +++ b/sysdeps/unix/sysv/linux/ntp_gettime.c
> @@ -40,7 +40,6 @@ __ntp_gettime64 (struct __ntptimeval64 *ntv)
>    ntv->time = tntx.time;
>    ntv->maxerror = tntx.maxerror;
>    ntv->esterror = tntx.esterror;
> -  ntv->tai = tntx.tai;
>    return result;
>  }
> 
> @@ -54,7 +53,10 @@ __ntp_gettime (struct ntptimeval *ntv)
>    int result;
> 
>    result = __ntp_gettime64 (&ntv64);
> -  *ntv = valid_ntptimeval64_to_ntptimeval (ntv64);
> +  //manually update fields to maintain abi with v2.11 struct definition

Sigh, so we decided to not add symbol versioning, and add ntp_gettimex
instead.

Comments should be in the form of '/* ... */', with first uppercase
and with final period.  

But I think we should make it clear that this function should not work
on 'struct ntptimeval', even though users might call glibc 2.12 version:

/* glibc 2.12 added the 'tai' field to follow along the kernel, but it did
   not add a compatibility symbol, instead it added __ntp_gettimex.  However
   ntptimeval was still used in both cases, so to keep compatibility it
   can not set all the new field.  */

struct old_ntptimeval
{
  struct timeval time;
  long int maxerror;
  long int esterror;
};

int
__old_ntp_gettime (struct old_ntptimeval *ntv)
{
  struct __ntptimeval64 ntv64;
  int result;

  result = __ntp_gettime64 (&ntv64);
  ntv->time = valid_timeval64_to_timeval (ntv64.time);
  ntv->maxerror = ntv64.maxerror;
  ntv->esterror = ntv64.esterror;

  return result;
}
strong_alias (__old_ntp_gettime, __ntp_gettime)


> +  ntv->time = valid_timeval64_to_timeval (ntv64.time);
> +  ntv->maxerror = ntv64.maxerror;
> +  ntv->esterror = ntv64.esterror;
> 
>    return result;
>  }