Re: [PATCH 1/2] sigaltstack: implement SS_AUTODISARM flag

[Stas Sergeev]

05.03.2016 10:39, Stas Sergeev ÐÐÑÐÑ:
> 05.03.2016 01:22, Andy Lutomirski ÐÐÑÐÑ:
> > On Mon, Feb 29, 2016 at 1:29 PM, Stas Sergeev <stsp@xxxxxxx> wrote:
> > > This patch implements the SS_AUTODISARM flag that can be ORed with
> > > SS_ONSTACK when forming ss_flags.
> > > When this flag is set, sigaltstack will be disabled when entering
> > > the signal handler; more precisely, after saving sas to uc_stack.
> > > When leaving the signal handler, the sigaltstack is restored by
> > > uc_stack.
> > > When this flag is used, it is safe to switch from sighandler with
> > > swapcontext(). Without this flag, the subsequent signal will corrupt
> > > the state of the switched-away sighandler.
> > This looks reasonable to me with one exception: how does a user
> > program detect the presence of this feature?
> Compile-time detection:
> #ifdef SS_AUTODISARM
>   # I have this feature
>   ...
> #endif
>
> Run-time detection:
> int err = sigaltstack(SS_ONSTACK | SS_AUTODISARM);
> if (err == EINVAL) {
I guess I mean here
if (err && errno == EINVAL)