From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Tim Schumacher <timschumi@gmx.de>
Cc: Jeff King <peff@peff.net>, git@vger.kernel.org, gitster@pobox.com
Subject: Re: [RFC PATCH v2] Allow aliases that include other aliases
Date: Thu, 06 Sep 2018 15:38:45 +0200 [thread overview]
Message-ID: <87r2i6rbiy.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <cd9a3a74-fdd6-0fb5-ae22-41d552391478@gmx.de>
On Wed, Sep 05 2018, Tim Schumacher wrote:
> On 05.09.18 19:34, Jeff King wrote:
>> On Wed, Sep 05, 2018 at 10:54:27AM +0200, Tim Schumacher wrote:
>>
>>> Aliases can only contain non-alias git commands and their
>>> arguments, not other user-defined aliases. Resolving further
>>> (nested) aliases is prevented by breaking the loop after the
>>> first alias was processed. Git then fails with a command-not-found
>>> error.
>>>
>>> Allow resolving nested aliases by not breaking the loop in
>>> run_argv() after the first alias was processed. Instead, continue
>>> incrementing `done_alias` until `handle_alias()` fails, which means that
>>> there are no further aliases that can be processed. Prevent looping
>>> aliases by storing substituted commands in `cmd_list` and checking if
>>> a command has been substituted previously.
>>> ---
>>>
>>> This is what I've come up with to prevent looping aliases. I'm not too
>>> happy with the number of indentations needed, but this seemed to be the
>>> easiest way to search an array for a value.
>>
>> I think this approach is OK, though I wonder if we'd also be fine with
>> just:
>>
>> if (done_alias++ > 100)
>> die("woah, is your alias looping?");
>>
>> The point is just to prevent a runaway infinite loop, and this does that
>> while keeping the cost very low for the common case (not that one string
>> insertion is probably breaking the bank).
>
> I'd opt to use the list-approach instead of aborting when the
> counter reaches 100 (or any other value), because it aborts
> at the earliest known looping point. I didn't run any tests
> comparing both solutions, but I assume the list would perform
> faster than the hard-limit, even if it requires slightly more
> memory and lines of code.
I agree that this use of a list is better for a completely different
reason (which I'll comment on in the v4 thread), but this reason doesn't
make any sense to me.
If we're looking at performance we're paying a fixed performance cost
for storing this list of strings over a counter for everything we do
with aliases.
It only helps over a counter for the case where we do have a loop, but
at that point who cares? We're going to exit with an erro anyway and the
user has to fix his config, it doesn't matter if that error happens 1
millisecond earlier.
next prev parent reply other threads:[~2018-09-06 13:38 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-05 8:54 [RFC PATCH v2] Allow aliases that include other aliases Tim Schumacher
2018-09-05 15:48 ` Duy Nguyen
2018-09-05 19:02 ` Tim Schumacher
2018-09-05 17:12 ` Junio C Hamano
2018-09-05 19:12 ` Tim Schumacher
2018-09-05 17:34 ` Jeff King
2018-09-05 20:02 ` Tim Schumacher
2018-09-06 13:38 ` Ævar Arnfjörð Bjarmason [this message]
2018-09-06 14:17 ` Ævar Arnfjörð Bjarmason
2018-10-18 22:57 ` [PATCH] alias: detect loops in mixed execution mode Ævar Arnfjörð Bjarmason
2018-10-19 8:28 ` Ævar Arnfjörð Bjarmason
2018-10-19 22:09 ` Jeff King
2018-10-20 10:52 ` Ævar Arnfjörð Bjarmason
2018-10-19 22:07 ` Jeff King
2018-10-20 11:14 ` Ævar Arnfjörð Bjarmason
2018-10-20 18:58 ` Jeff King
2018-10-20 19:18 ` Ævar Arnfjörð Bjarmason
2018-10-22 21:15 ` Jeff King
2018-10-22 21:28 ` Ævar Arnfjörð Bjarmason
2018-10-22 1:23 ` Junio C Hamano
2018-10-26 8:39 ` Jeff King
2018-10-26 12:44 ` Ævar Arnfjörð Bjarmason
2018-10-29 3:44 ` Junio C Hamano
2018-10-29 14:17 ` Jeff King
2018-09-05 21:51 ` [RFC PATCH v2] Allow aliases that include other aliases Junio C Hamano
2018-09-06 10:16 ` [PATCH v3] " Tim Schumacher
2018-09-06 14:01 ` Ævar Arnfjörð Bjarmason
2018-09-06 14:57 ` Jeff King
2018-09-06 15:10 ` Ævar Arnfjörð Bjarmason
2018-09-06 16:18 ` Jeff King
2018-09-06 19:05 ` Tim Schumacher
2018-09-06 19:17 ` Jeff King
2018-09-06 14:59 ` Jeff King
2018-09-06 18:40 ` Junio C Hamano
2018-09-06 19:05 ` Jeff King
2018-09-06 19:31 ` Tim Schumacher
2018-09-07 22:44 ` [RFC PATCH v4 1/3] Add support for nested aliases Tim Schumacher
2018-09-07 22:44 ` [RFC PATCH v4 2/3] Show the call history when an alias is looping Tim Schumacher
2018-09-08 13:34 ` Duy Nguyen
2018-09-08 16:29 ` Jeff King
2018-09-07 22:44 ` [RFC PATCH v4 3/3] t0014: Introduce alias testing suite Tim Schumacher
2018-09-07 23:38 ` Eric Sunshine
2018-09-14 23:12 ` Tim Schumacher
2018-09-16 7:21 ` Eric Sunshine
2018-09-08 13:28 ` [RFC PATCH v4 1/3] Add support for nested aliases Duy Nguyen
2018-09-16 7:46 ` Tim Schumacher
2018-09-17 15:37 ` Junio C Hamano
2018-09-21 12:45 ` Tim Schumacher
2018-09-21 15:59 ` Junio C Hamano
2018-09-16 7:50 ` [PATCH v5 " Tim Schumacher
2018-09-16 7:50 ` [PATCH v5 2/3] Show the call history when an alias is looping Tim Schumacher
2018-09-16 7:50 ` [PATCH v5 3/3] t0014: Introduce an alias testing suite Tim Schumacher
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