From: Derrick Stolee <stolee@gmail.com>
To: Duy Nguyen <pclouds@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
Stefan Beller <sbeller@google.com>,
Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH 07/14] parse-options: allow ll_callback with OPTION_CALLBACK
Date: Tue, 16 Apr 2019 10:24:39 -0400 [thread overview]
Message-ID: <6b731f57-eada-8c1c-8e5d-de386b0c414e@gmail.com> (raw)
In-Reply-To: <CACsJy8DDKuK5VYhh0GNYSJK1_y3MZgK5Vcq99N4jYcusVFnvQQ@mail.gmail.com>
On 4/16/2019 4:52 AM, Duy Nguyen wrote:
> On Mon, Apr 15, 2019 at 9:06 PM Derrick Stolee <stolee@gmail.com> wrote:
>>
>> On 1/26/2019 7:35 PM, Nguyễn Thái Ngọc Duy wrote:
>>> @@ -238,7 +249,10 @@ static enum parse_opt_result parse_short_opt(struct parse_opt_ctx_t *p,
>>> len++;
>>> arg = xmemdupz(p->opt, len);
>>> p->opt = p->opt[len] ? p->opt + len : NULL;
>>> - rc = (*numopt->callback)(numopt, arg, 0) ? (-1) : 0;
>>> + if (numopt->callback)
>>> + rc = (*numopt->callback)(numopt, arg, 0) ? (-1) : 0;
>>> + else
>>> + rc = (*numopt->ll_callback)(p, numopt, arg, 0);
>>> free(arg);
>>> return rc;
>>> }
>>
>> Hi Duy,
>>
>> This "else" condition is unreachable. This block is only hit when we have a "-<n>"
>> option, using OPT_NUMBER_CALLBACK, which is implemented by filling "callback", never
>> "ll_callback".
>
> It does not mean ll_callback cannot be used in the future though.
That's not a very good reason to add it now. YAGNI.
> We
> have three options
>
> 1. drop the else clause
> 2. replace with "else BUG();"
> 3. implement proper else clause
>
> Option #1 to me sounds wrong. If you don't support something, yell up.
> Silently ignoring it only makes it harder to track down to this
> unsupported location when it becomes reachable, however unlikely that
> is.
>
> Which leaves options #2 and #3. If you think this one line is risky
> enough, I'll send a patch to replace it with BUG().
It's not about risk, but the fact that it is pointless. The only way to get to
this block is to create a 'struct option' with type OPTION_NUMBER manually
(ignoring the OPT_NUMBER_CALLBACK macro), which _should_ be unsupported. If
someone goes to the pain of adding a way to instantiate with a low-level callback,
then they should add this 'if' statement.
If you are going to add protection from an incorrect instantiation of 'callback'
in a use of OPT_NUMBER_CALLBACK, then the proper place to do that is probably in
parse_options_check(), where you were already doing callback-vs-ll_callback checks
in the case of OPTION_CALLBACK and OPTION_LOWLEVEL_CALLBACK.
However, the only places where the OPT_NUMBER_CALLBACK option appears are
builtin/grep.c and t/helper/test-parse-options.c. I don't imagine a need to
add low-level callbacks any time soon.
>> I recommend reverting this diff segment, but please let me know if I'm missing something.
I still think this is the easiest way to remove the dead code.
I'll try to submit a patch later. I'm still not in full work mode, so I may be slow.
Thanks,
-Stolee
next prev parent reply other threads:[~2019-04-16 14:24 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-27 0:35 [PATCH 00/14] nd/diff-parseopt part 1 Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 01/14] parse-options.h: remove extern on function prototypes Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 02/14] parse-options: add one-shot mode Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 03/14] parse-options: disable option abbreviation with PARSE_OPT_KEEP_UNKNOWN Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 04/14] parse-options: add OPT_BITOP() Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 05/14] parse-options: stop abusing 'callback' for lowlevel callbacks Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 06/14] parse-options: avoid magic return codes Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 07/14] parse-options: allow ll_callback with OPTION_CALLBACK Nguyễn Thái Ngọc Duy
2019-04-15 14:06 ` Derrick Stolee
2019-04-16 8:52 ` Duy Nguyen
2019-04-16 14:24 ` Derrick Stolee [this message]
2019-01-27 0:35 ` [PATCH 08/14] diff.h: keep forward struct declarations sorted Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 09/14] diff.h: avoid bit fields in struct diff_flags Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 10/14] diff.c: prepare to use parse_options() for parsing Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 11/14] diff.c: convert -u|-p|--patch Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 12/14] diff.c: convert -U|--unified Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 13/14] diff.c: convert -W|--[no-]function-context Nguyễn Thái Ngọc Duy
2019-01-27 0:35 ` [PATCH 14/14] diff.c: convert --raw Nguyễn Thái Ngọc Duy
2019-01-28 0:33 ` [PATCH 00/14] nd/diff-parseopt part 1 Junio C Hamano
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