Re: [PATCH] sparse: ignore warning from new glibc headers

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 18, 2024, 07:07 UTC
Message-ID: <xmqqzfqfyy7q.fsf@gitster.g>
In-Reply-To: <ZpiAcJuAH50UlHIX@danh.dev>

Đoàn Trần Công Danh <congdanhqx@gmail.com> writes:

Show 9 quoted lines

>> BTW, I didn't expect it to take this long for this issue to come
>> back to the list! I expected it to almost immediately cause
>> problems with the sparse ci job, when the version of Ubuntu was
>> updated to the LTS (now previous LTS!). So, I just found a simple
>> solution for now (which turned into 2 years).
>
> Well, yeah, -Wno-vla would work, I used that macro __STDC_NO_VLA__
> because I'm not sure Git want to use vla or not, so I only tried to
> disable it for system headers.

Defining __STDC_NO_VLA__ would rid use of variable length arrays in the regex.h header, so "-Wno-vla" would not be necessary. It's just that it makes me feel a bit dirty to define the macro that only compiler implementations are expected to define in order to cause header files behave the way they would with a compiler without VLA.

If we apply Luc's patch [*1*] to sparse, the header would use vla in parameter in the prototype, sparse would grok it, *and* then complain that we are using vla, so we still need "-Wno-vla" on top (but "-Wno-vla" alone would not make (unpatched) sparse grok the construct, of course).

> And yes, the vla declarationw as added into glibc 2.35.

Thanks.

[Reference]

*1* https://lore.kernel.org/all/uug4xslokvlxr6z24q52z4pt7nrtiimbzunz2gz3kpilk4kxts@7jljsksi6baq/