From: Eric Gallager <egall@gwmail.gwu.edu>
To: Jonathan Wakely <jwakely.gcc@gmail.com>
Cc: Julian Waters <tanksherman27@gmail.com>,
Andrew Pinski <pinskia@gmail.com>,
gcc@gcc.gnu.org
Subject: Re: Warning specifically for a returning noreturn
Date: Wed, 5 Jul 2023 12:50:29 -0400 [thread overview]
Message-ID: <CAMfHzOuhWsUqbqw4kUHy=A5ZuJzGA1zM6Vx3hAUkPrKyL1k4EQ@mail.gmail.com> (raw)
In-Reply-To: <CAH6eHdQU3=i9P=SgU85xkBWB5VbP6c32o5E+3FPumB5uZQ5LbA@mail.gmail.com>
On Wed, Jul 5, 2023 at 7:28 AM Jonathan Wakely via Gcc <gcc@gcc.gnu.org> wrote:
>
> On Wed, 5 Jul 2023 at 12:01, Julian Waters via Gcc <gcc@gcc.gnu.org> wrote:
> >
> > I see, thanks Andrew.
> >
> > Anyone else have opinions on this besides Liu or Andrew? The responses have
> > been surprisingly quiet thus far
>
> IMHO all warnings should have an option controlling them, so that you
> can disable them via pragmas.
>
This is bug 44209, for reference:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44209
> But I agree that you shouldn't need to return from a noreturn
> function, it can either throw or use __builtin_unreachable() on the
> line where you currently return.
>
>
> >
> > best regards,
> > Julian
> >
> > On Wed, 5 Jul 2023, 09:40 Andrew Pinski, <pinskia@gmail.com> wrote:
> >
> > > On Tue, Jul 4, 2023 at 6:32 PM Julian Waters <tanksherman27@gmail.com>
> > > wrote:
> > > >
> > > > Hi Andrew, thanks for the quick response,
> > > >
> > > > What if the method has a return value? I know it sounds
> > > counterintuitive, but in some places HotSpot relies on the noreturn
> > > attribute being applied to methods that do return a value in an unreachable
> > > code path. Does the unreachable builtin cover that case too?
> > >
> > > It is wrong to use noreturn on a function other than one which has a
> > > return type of void as documented.
> > >
> > > https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-noreturn-function-attribute
> > > :
> > > ```
> > > It does not make sense for a noreturn function to have a return type
> > > other than void.
> > > ```
> > >
> > > Thanks,
> > > Andrew Pinski
> > >
> > >
> > > >
> > > > best regards.
> > > > Julian
> > > >
> > > > On Wed, Jul 5, 2023 at 9:07 AM Andrew Pinski <pinskia@gmail.com> wrote:
> > > >>
> > > >> On Tue, Jul 4, 2023 at 5:54 PM Julian Waters via Gcc <gcc@gcc.gnu.org>
> > > wrote:
> > > >> >
> > > >> > Hi all,
> > > >> >
> > > >> > Currently to disable the warning that a noreturn method does return,
> > > it's
> > > >> > required to disable warnings entirely. This can be very inconvenient
> > > when
> > > >> > -Werror is enabled with a noreturn method that isn't specifically
> > > calling
> > > >> > something like std::abort() at the end, when one wants all other
> > > -Wall and
> > > >> > -Wextra warnings to be reported, for instance in the Java HotSpot VM
> > > (which
> > > >> > I'm currently adapting to compile with gcc on all supported
> > > platforms). Is
> > > >> > there a possibility we can add a disable warning option specifically
> > > for
> > > >> > this case? Something like -Wno-returning-noreturn. I'm interested in
> > > adding
> > > >> > this myself if it's not convenient for gcc's maintainers to do so at
> > > the
> > > >> > moment, but I'd need some guidance on where to look and what the
> > > relevant
> > > >> > code is
> > > >>
> > > >> You could just add
> > > >> __builtin_unreachable(); (or std::unreachable(); if you are C++23 or
> > > >> unreachable() if you are using C23).
> > > >> Or even add while(true) ;
> > > >>
> > > >> I am pretty sure not having an option is on purpose and not really
> > > >> interested in adding an option here because of the above workarounds.
> > > >>
> > > >> Thanks,
> > > >> Andrew Pinski
> > > >>
> > > >> >
> > > >> > best regards,
> > > >> > Julian
> > >
prev parent reply other threads:[~2023-07-05 16:50 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-05 0:52 Julian Waters
2023-07-05 1:07 ` Andrew Pinski
2023-07-05 1:31 ` Julian Waters
2023-07-05 1:40 ` Andrew Pinski
2023-07-05 5:40 ` LIU Hao
2023-07-05 11:00 ` Julian Waters
2023-07-05 11:26 ` Jonathan Wakely
2023-07-05 13:13 ` Julian Waters
2023-07-05 13:20 ` Jonathan Wakely
2023-07-21 3:26 ` Julian Waters
2023-07-21 9:43 ` Jonathan Wakely
2023-07-25 2:38 ` Julian Waters
2023-07-05 16:50 ` Eric Gallager [this message]
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