Hi Georg,

> Date: 2026-10-27 01:37:11+0100
> From: Georg Sauthoff <mail@gms.tf>
>
> GNU libc declares clock_adjtime() when including time.h, and not when
> just sys/timex.h is included, iff support for GNU features is requested.
> 
> Verification:
> 
>     $ for i in BLAH _GNU_SOURCE; do for j in sys/timex.h time.h; do echo -n "Testing $i and $j ... "; echo -e '#define '"$i"'\n#include <'"$j"'>\nvoid f(){clock_adjtime;}' | gcc  -xc - -o /dev/null -c 2>/dev/null && echo OK || echo FAIL; done; done
>     Testing BLAH and sys/timex.h ... FAIL
>     Testing BLAH and time.h ... FAIL
>     Testing _GNU_SOURCE and sys/timex.h ... FAIL
>     Testing _GNU_SOURCE and time.h ... OK
> 
> (Test output is from a Fedora 43 system)
> 
> Signed-off-by: Georg Sauthoff <mail@gms.tf>

Thanks!  I've applied the patch.


Have a lovely day!
Alex

> ---
>  man/man2/adjtimex.2 | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/man/man2/adjtimex.2 b/man/man2/adjtimex.2
> index f12d9413e..5b9a0667b 100644
> --- a/man/man2/adjtimex.2
> +++ b/man/man2/adjtimex.2
> @@ -17,9 +17,12 @@ .SH SYNOPSIS
>  .P
>  .BI "int adjtimex(struct timex *" "buf" );
>  .P
> -.BI "int clock_adjtime(clockid_t " clk_id, " struct timex *" "buf" );
> -.P
>  .BI "int ntp_adjtime(struct timex *" buf );
> +.P
> +.BR #define\~_GNU_SOURCE "  // See feature_test_macros(7)"
> +.B #include <time.h>
> +.P
> +.BI "int clock_adjtime(clockid_t " clk_id, " struct timex *" "buf" );
>  .fi
>  .SH DESCRIPTION
>  Linux uses David L.\& Mills' clock adjustment algorithm (see RFC\ 5905).
> -- 
> 2.55.0
> 
> 

-- 
<https://www.alejandro-colomar.es>