Re: [PATCH] linux-user: Remove unnecessary static assert involving __SIGRTMAX

[Laurent Vivier]

Le 26/05/2021 à 19:16, Philippe Mathieu-Daudé a écrit :
> On 5/26/21 6:39 AM, Michael Forney wrote:
>> Since "linux-user: fix use of SIGRTMIN" (6bc024e7), qemu removed
>> use of __SIGRTMAX except for in this QEMU_BUILD_BUG_ON assert.
>> Presumably, this check is to ensure that the loop in signal_table_init
>> from SIGRTMIN to SIGRTMAX falls within the bounds of
>> host_to_target_signal_table (_NSIG).
>>
>> However, _NSIG is already defined to be the one larger than the
>> largest signal supported by the system (as specified in the upcoming
>> POSIX revision[0]), so the check is unnecessary.
>>
>> musl libc does not define __SIGRTMAX, so removing this check fixes
>> one of the last remaining errors when building qemu.
>>
>> [0] https://www.austingroupbugs.net/view.php?id=741
>>
>> Signed-off-by: Michael Forney <mforney@mforney.org>
>> ---
>> If you prefer, I can send an alternate patch to leave the
>> QEMU_BUILD_BUG_ON, but guard it by #ifdef __SIGRTMAX.
> 
> This looks safer, personally I prefer, but let's see what the
> maintainers prefer.

I agree, the reason of the check is explained in the comment above.

I think it's safer to keep the QEMU_BUILD_BUG_ON().

In the past we had a confusion between _NSIG, NSIG and TARGET_NSIG.

See 9fcff3a67f2b ("linux-user: fix TARGET_NSIG and _NSIG uses")

Thanks,
Laurent