Re: raise() marked __leaf__ is not C-compliant?

[Tadeus Prastowo <0x66726565@gmail.com>]

On Wed, Oct 28, 2020 at 12:53 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> On 28/10/2020 04:33, Tadeus Prastowo wrote:
> >
> > I meant to say: Glibc-2.30 raise() definitely runs a signal handler,
> > and the signal handler can be defined in the current compilation unit
> > to use static variables.  So, unless the C standard says that
> > accessing a non-volatile object with static storage duration from
> > within a signal handler that is called synchronously using raise() on
> > a normal execution path is an undefined behavior, the marking of
> > raise() with __leaf__ makes raise() non-compliant with the C standard.
> >
> >> May I know your opinion, please?
>
> The sentence "raise() definitely runs a signal handler" is not really
> valid in a portable sense. Afaik neither C nor POSIX states which signals
> should be delivered synchronously or asynchronously (although some do
> only make sense to be delivered synchronously such as SIGSEGV).
>
> However, Linux does ran some signals synchronously and I agree that using
> leaf attribute is incorrect and lead to this kind of problems. My point is
> to be fully portable, you need to assume any signal might be delivered
> asynchronously (and C standard specifies the volatile sig_atomic_t for
> such cases).

Thank you for your response.

However, C, including C99, C11, and the latest C18 [1], says: "If a
signal handler is called, the raise function shall not return until
after the signal handler does."  And, POSIX [2] says: "If a signal
handler is called, the raise() function shall not return until after
the signal handler does."  So, the sentence "raise() definitely runs a
signal handler" is valid in a portable sense as required by the
standards, no?

[1] Page 195 of
https://web.archive.org/web/20181230041359/http://www.open-std.org/jtc1/sc22/wg14/www/abq/c17_updated_proposed_fdis.pdf
[2] The raise section of Chapter 3 "System Interfaces" of IEEE
Standard for Information Technology---POSIX, Volume 2 "System
Interfaces", Issue 7.

-- 
Best regards,
Tadeus