Subject: Re: [PATCH] t8002-blame: simplify padding generation in blank boundary tests

From: Junio C Hamano <[email-masked]>
Date: Mon, 13 Jan 2025 07:15:28 -0800

Patrick Steinhardt <[email-masked]> writes:

> On Sun, Jan 12, 2025 at 12:11:07AM +0100, Jan Palus wrote:
>> Fixes compatibility with mksh as well:
>> $ mksh -c 'printf "%0.s" ""'
>> printf: %0.s: invalid conversion specification
>> 
>> Fixes: e7fb2ca945 ("builtin/blame: fix out-of-bounds write with blank boundary commits")
>
> We don't typically use Fixes tags in our project, but instead embed the
> commit into the commit message with `git log --format=reference -1`
> together with a description.
>
> The subject can also be adjusted a bit: we use to just write the test
> number, and the important aspect is not that we simplify the padding
> generation, but that we make it more portable.
>
> So, my suggestion would be:
>
>     t8002: fix unportable printf formatting directives
>
>     In e7fb2ca945 (builtin/blame: fix out-of-bounds write with blank
>     boundary commits, 2025-01-10), we have introduced two new tests that
>     expect a certain amount of padding. This padding is generated via
>     printf using the "%0.s" formatting directive. That directive is
>     non-portable and not understood by for example mksh, breaking these
>     tests on platforms using that shell.
>
>     Fix this issue by using "%${N}s" instead, which is already being
>     used in t5300 and thus portable enough for us.

Is "%.0s" really not portable, or is it just mksh
being a bit lacking?

"That directive non-portable ..." -> "Some implementations (e.g.
one that is built into mksh) does not support the precision to be 0
(i.e. "%.0" before the "s" conversion)"

Other than that, your version is easy to read and understand.

>> -	$(printf "%0.s " $(test_seq 11)) (<[email-masked]> 2005-04-07 15:45:13 -0700 1) abbrev
>> +	$(printf "%11s" "") (<[email-masked]> 2005-04-07 15:45:13 -0700 1) abbrev
>>  	EOF
>>  	git blame -b --abbrev=10 ^HEAD -- abbrev.t >actual &&
>>  	test_cmp expect actual
>
> Okay, makes sense. And as mentioned, we already have such a use of
> printf in t5300, so it should be portable enough for our use case.

Thanks for reviewing, and thanks, Jan, for noticing and fixing.