Re: [PATCH 1/5] compat/obstack: fix -Wcast-function-type warnings

From: Junio C Hamano <gitster@pobox.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>,
	"Jonathan Nieder" <jrnieder@gmail.com>,
	"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
	git@vger.kernel.org
Subject: Re: [PATCH 1/5] compat/obstack: fix -Wcast-function-type warnings
Date: Thu, 10 Jan 2019 13:22:00 -0800	[thread overview]
Message-ID: <xmqqef9k1a4n.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <87zhszeqsr.fsf@evledraar.gmail.com> (=?utf-8?B?IsOGdmFyIEFy?= =?utf-8?B?bmZqw7Zyw7A=?= Bjarmason"'s message of "Fri, 21 Dec 2018 00:12:20 +0100")

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> On Thu, Dec 20 2018, SZEDER Gábor wrote:
>
>> When building Git with GCC 8.2.0 (at least from Homebrew on macOS,
>> DEVELOPER flags enabled) one is greeted with a screenful of compiler
>> errors:
>>
>>   compat/obstack.c: In function '_obstack_begin':
>>   compat/obstack.c:162:17: error: cast between incompatible function types from 'void * (*)(long int)' to 'struct _obstack_chunk * (*)(void *, long int)' [-Werror=cast-function-type]
>>      h->chunkfun = (struct _obstack_chunk * (*)(void *, long)) chunkfun;
>>                    ^
>>   compat/obstack.c:163:16: error: cast between incompatible function types from 'void (*)(void *)' to 'void (*)(void *, struct _obstack_chunk *)' [-Werror=cast-function-type]
>>      h->freefun = (void (*) (void *, struct _obstack_chunk *)) freefun;
>>                   ^
>>   compat/obstack.c:116:8: error: cast between incompatible function types from 'struct _obstack_chunk * (*)(void *, long int)' to 'struct _obstack_chunk * (*)(long int)' [-Werror=cast-function-type]
>>       : (*(struct _obstack_chunk *(*) (long)) (h)->chunkfun) ((size)))
>>           ^
>>   compat/obstack.c:168:22: note: in expansion of macro 'CALL_CHUNKFUN'
>>      chunk = h->chunk = CALL_CHUNKFUN (h, h -> chunk_size);
>>                         ^~~~~~~~~~~~~
>>   <snip>
>
> We originally got this from now-discontinued eglibc, but I notice that
> glibc.git's malloc/obstack.[ch]'s diff also changes these lines. If you
> backport those do does that fix this warning?
>
> I.e. is this another case where we're blindly fixing bugs but should
> just re-import upstream's code instead?

Good point.  I am inclined to queue the remainder of the series
without this one for now.

Thanks.