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From: Derrick Stolee <derrickstolee@github.com>
To: Junio C Hamano <gitster@pobox.com>,
	Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, vdye@github.com,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Subject: Re: [PATCH v3 1/3] maintenance: add 'unregister --force'
Date: Tue, 27 Sep 2022 07:54:38 -0400	[thread overview]
Message-ID: <63aa68fb-c215-a79f-e3c6-1c1a489220e2@github.com> (raw)
In-Reply-To: <b1e6f118-046c-42f8-01a8-2543e792685a@github.com>

On 9/27/2022 7:38 AM, Derrick Stolee wrote:
> On 9/26/2022 5:55 PM, Junio C Hamano wrote:
>> "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com> writes:
>>
>>> @@ -1538,11 +1546,23 @@ static int maintenance_unregister(int argc, const char **argv, const char *prefi
>>>  		usage_with_options(builtin_maintenance_unregister_usage,
>>>  				   options);
>>>  
>>> -	config_unset.git_cmd = 1;
>>> -	strvec_pushl(&config_unset.args, "config", "--global", "--unset",
>>> -		     "--fixed-value", "maintenance.repo", maintpath, NULL);
>>> +	for_each_string_list_item(item, list) {
>>> +		if (!strcmp(maintpath, item->string)) {
>>> +			found = 1;
>>> +			break;
>>> +		}
>>> +	}
>>
>> Just out of curiosity, I ran this in a fresh repository and got a
>> segfault.
> 
> Yikes! Thanks for catching. I think there was another instance in
> the 'register' code that I caught by tests, but I appreciate you
> catching this one.
> 
>>  An attached patch obviously fixes it, but I am wondering
>> if a better "fix" is to teach for_each_string_list_item() that it is
>> perfectly reasonable to see a NULL passed to it as the list, which
>> is a mere special case that the caller has a string list with 0
>> items on it.
>>
>> Thoughts?
> 
> I agree that for_each_string_list_item() could handle NULL lists
> better, especially because it looks like a method and hides some
> details. Plus, wrapping the for-ish loop with an if statement is
> particularly ugly.
...
> I'll get a patch put together that changes the behavior of
> for_each_string_list_item() and adds the missing 'unregister' test
> so we can avoid this problem.

Of course, there is a reason why we don't check for NULL here,
and it's because -Werror=address complains when we use a non-pointer
value in the macro:

string-list.h:146:28: error: the address of ‘friendly_ref_names’ will always evaluate as ‘true’ [-Werror=address]
  146 |         for (item = (list) ? (list)->items : NULL;      \
      |

I tried searching for a way to suppress this error in a particular
case like this (perhaps using something like an attribute?), but I
couldn't find anything.

Thanks,
-Stolee

  reply	other threads:[~2022-09-27 11:55 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-20  1:02 [PATCH] maintenance: make unregister idempotent Derrick Stolee via GitGitGadget
2022-09-21 17:19 ` Junio C Hamano
2022-09-22 12:37   ` Derrick Stolee
2022-09-22 19:31     ` Junio C Hamano
2022-09-22 19:46       ` Derrick Stolee
2022-09-22 20:44         ` Junio C Hamano
2022-09-22 13:37 ` [PATCH v2 0/2] scalar: " Derrick Stolee via GitGitGadget
2022-09-22 13:37   ` [PATCH v2 1/2] maintenance: add 'unregister --force' Derrick Stolee via GitGitGadget
2022-09-23 13:08     ` SZEDER Gábor
2022-09-26 13:32       ` Derrick Stolee
2022-09-26 15:39         ` Ævar Arnfjörð Bjarmason
2022-09-26 17:25           ` Derrick Stolee
2022-09-26 19:17             ` Junio C Hamano
2022-09-22 13:37   ` [PATCH v2 2/2] scalar: make 'unregister' idempotent Derrick Stolee via GitGitGadget
2022-09-26 18:48   ` [PATCH v3 0/3] scalar: make unregister idempotent Derrick Stolee via GitGitGadget
2022-09-26 18:48     ` [PATCH v3 1/3] maintenance: add 'unregister --force' Derrick Stolee via GitGitGadget
2022-09-26 19:23       ` Junio C Hamano
2022-09-26 20:49         ` Derrick Stolee
2022-09-26 21:55       ` Junio C Hamano
2022-09-27 11:38         ` Derrick Stolee
2022-09-27 11:54           ` Derrick Stolee [this message]
2022-09-27 13:36             ` Ævar Arnfjörð Bjarmason
2022-09-27 13:55               ` Derrick Stolee
2022-09-26 18:48     ` [PATCH v3 2/3] scalar: make 'unregister' idempotent Derrick Stolee via GitGitGadget
2022-09-26 18:48     ` [PATCH v3 3/3] gc: replace config subprocesses with API calls Derrick Stolee via GitGitGadget
2022-09-26 19:27       ` Junio C Hamano
2022-09-27 13:56     ` [PATCH v4 0/4] scalar: make unregister idempotent Derrick Stolee via GitGitGadget
2022-09-27 13:56       ` [PATCH v4 1/4] maintenance: add 'unregister --force' Derrick Stolee via GitGitGadget
2022-09-27 13:56       ` [PATCH v4 2/4] scalar: make 'unregister' idempotent Derrick Stolee via GitGitGadget
2022-09-27 13:57       ` [PATCH v4 3/4] gc: replace config subprocesses with API calls Derrick Stolee via GitGitGadget
2022-09-27 13:57       ` [PATCH v4 4/4] string-list: document iterator behavior on NULL input Derrick Stolee via GitGitGadget
2022-09-27 16:39         ` Junio C Hamano
2022-09-27 16:31       ` [PATCH v4 0/4] scalar: make unregister idempotent Junio C Hamano
2022-09-27 16:54         ` Derrick Stolee

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