[uml-devel] Warning in syscall_trace_enter

[uml-devel] Warning in syscall_trace_enter

[Lorenzo Colitti]

Hi,

when compiling UML with -Wall -Werror, I get:

arch/um/kernel/ptrace.c: In function ‘syscall_trace_enter’:
arch/um/kernel/ptrace.c:178:32: warning: ignoring return value of
‘tracehook_report_syscall_entry’, declared with attribute
warn_unused_result [-Wunused-result]
error, forbidden warning: ptrace.c:178
make[1]: *** [arch/um/kernel/ptrace.o] Error 1

This code hasn't changed in a long time (since 1bfa2317 in May 2012, I
think), so I assume this is intentional?

Any thoughts on whether you'd like to fix this upstream, and if so
how? I can put a trivial fix into our trees (assign the result to a
dummy variable, or do "if (tracehook_report_syscall_entry()) return;")
but if you're thinking of fixing it upstream I should probably wait to
cherry-pick whatever fix you decide on. Just putting (void) in front
of the function does not silence the warning gcc. (This is apparently
working as intended - see
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509#c26 )

Thanks,
Lorenzo

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Re: [uml-devel] Warning in syscall_trace_enter

[Richard Weinberger]

On Tue, Mar 3, 2015 at 5:55 AM, Lorenzo Colitti <lorenzo@google.com> wrote:
> Hi,
>
> when compiling UML with -Wall -Werror, I get:

Don't build with -Werror.

> arch/um/kernel/ptrace.c: In function ‘syscall_trace_enter’:
> arch/um/kernel/ptrace.c:178:32: warning: ignoring return value of
> ‘tracehook_report_syscall_entry’, declared with attribute
> warn_unused_result [-Wunused-result]
> error, forbidden warning: ptrace.c:178
> make[1]: *** [arch/um/kernel/ptrace.o] Error 1
>
> This code hasn't changed in a long time (since 1bfa2317 in May 2012, I
> think), so I assume this is intentional?
>
> Any thoughts on whether you'd like to fix this upstream, and if so
> how? I can put a trivial fix into our trees (assign the result to a
> dummy variable, or do "if (tracehook_report_syscall_entry()) return;")
> but if you're thinking of fixing it upstream I should probably wait to
> cherry-pick whatever fix you decide on. Just putting (void) in front
> of the function does not silence the warning gcc. (This is apparently
> working as intended - see
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509#c26 )

IIRC the big plan is to make tracehook_report_syscall_entry() tree-wide void.

-- 
Thanks,
//richard

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Re: [uml-devel] Warning in syscall_trace_enter

[Lorenzo Colitti]

On Tue, Mar 3, 2015 at 5:32 PM, Richard Weinberger
<richard.weinberger@gmail.com> wrote:
> IIRC the big plan is to make tracehook_report_syscall_entry() tree-wide void.

Ack, thanks. In the meantime, for trees we already build with -Werror,
we'll put a temporary local hack in place.

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Re: [uml-devel] Warning in syscall_trace_enter

[Richard Weinberger]

Am 03.03.2015 um 09:39 schrieb Lorenzo Colitti:
> On Tue, Mar 3, 2015 at 5:32 PM, Richard Weinberger
> <richard.weinberger@gmail.com> wrote:
>> IIRC the big plan is to make tracehook_report_syscall_entry() tree-wide void.
> 
> Ack, thanks. In the meantime, for trees we already build with -Werror,
> we'll put a temporary local hack in place.

As long GCC has a shitload of completely useless warnings building with -Werror
is just a PITA. That's why Linux does not use that flag. :-)

Thanks,
//richard

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Re: [uml-devel] Warning in syscall_trace_enter

[Geert Uytterhoeven]

On Tue, Mar 3, 2015 at 9:48 AM, Richard Weinberger <richard@nod.at> wrote:
> Am 03.03.2015 um 09:39 schrieb Lorenzo Colitti:
>> On Tue, Mar 3, 2015 at 5:32 PM, Richard Weinberger
>> <richard.weinberger@gmail.com> wrote:
>>> IIRC the big plan is to make tracehook_report_syscall_entry() tree-wide void.
>>
>> Ack, thanks. In the meantime, for trees we already build with -Werror,
>> we'll put a temporary local hack in place.
>
> As long GCC has a shitload of completely useless warnings building with -Werror
> is just a PITA. That's why Linux does not use that flag. :-)

For some classes of warnings yet.

For this particular case, given the tree-wide void plan, it can easily be
resolved by dropping the __must_check attribute from
tracehook_report_syscall_entry() now.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [uml-devel] Warning in syscall_trace_enter

[Richard Weinberger]

Am 03.03.2015 um 10:26 schrieb Geert Uytterhoeven:
> On Tue, Mar 3, 2015 at 9:48 AM, Richard Weinberger <richard@nod.at> wrote:
>> Am 03.03.2015 um 09:39 schrieb Lorenzo Colitti:
>>> On Tue, Mar 3, 2015 at 5:32 PM, Richard Weinberger
>>> <richard.weinberger@gmail.com> wrote:
>>>> IIRC the big plan is to make tracehook_report_syscall_entry() tree-wide void.
>>>
>>> Ack, thanks. In the meantime, for trees we already build with -Werror,
>>> we'll put a temporary local hack in place.
>>
>> As long GCC has a shitload of completely useless warnings building with -Werror
>> is just a PITA. That's why Linux does not use that flag. :-)
> 
> For some classes of warnings yet.
> 
> For this particular case, given the tree-wide void plan, it can easily be
> resolved by dropping the __must_check attribute from
> tracehook_report_syscall_entry() now.

Yep. Currently I'm searching the archives for that plan.
I was about to fix that warning a few months ago but I was told
that is not needed...

Thanks,
//richard