Hello Thomas,
On 5/30/23 18:40, Thomas Weißschuh wrote:
> POSIX does not allow "tv" to be NULL.
>
> On glibc and gnulib calling gettimeofday(NULL, NULL) can segfault.
>
> For glibc see __gettimeofday() and __gettimeofday64() in
> sysdeps/unix/sysv/linux/gettimeofday.c.
>
> Note that by default glibc may use the gettimeofday() syscall or vdso
> function which both support "tv" to be NULL.
> The segfault can be triggered by compiling a i386 binary on a x86_64
> system.
What happens with the Linux syscall? What does it do for NULL in tv?
Thanks,
Alex
>
> Signed-off-by: Thomas Weißschuh <thomas@xxxxxxxx>
> ---
> man2/gettimeofday.2 | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/man2/gettimeofday.2 b/man2/gettimeofday.2
> index 9d134fa49de7..cdbec5ede23c 100644
> --- a/man2/gettimeofday.2
> +++ b/man2/gettimeofday.2
> @@ -85,16 +85,14 @@ struct timezone {
> .EE
> .in
> .PP
> -If either
> -.I tv
> -or
> +If
> .I tz
> -is NULL, the corresponding structure is not set or returned.
> +is NULL, the structure is not set or returned.
> .\" FIXME . The compilation warning looks to be going away in glibc 2.17
> .\" see glibc commit 4b7634a5e03b0da6f8875de9d3f74c1cf6f2a6e8
> -(However, compilation warnings will result if
> +If
> .I tv
> -is NULL.)
> +is NULL, the behavior is unspecified.
> .\" The following is covered under EPERM below:
> .\" .PP
> .\" Only the superuser may use
>
> ---
> base-commit: f0067f73941ea0e512b9018a123472508a0858db
> change-id: 20230530-gettimeofday-null-7ee404b7825f
>
> Best regards,
--
<http://www.alejandro-colomar.es/>
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