Re: [PATCH v2 1/2] t4205: compare huge output without diff

From: Patrick Steinhardt <ps@pks.im>
Date: Sep 28, 2026, 06:36 UTC
Message-ID: <aroK5js5U2t0IUIc@pks.im>
In-Reply-To: <20260925-ci-large-test-resources-v2-1-f632cf319756@gmail.com>

On Fri, Sep 25, 2026 at 12:35:38PM -0400, Tamir Duberstein wrote:

Show 10 quoted lines

> The huge-commit test compares output containing a line larger than 2 GiB.
> For two identical files containing 2,147,483,649 "1" bytes followed by
> "0\n", GNU diffutils 3.8 on Linux arm64 gives these measurements:
> 
>   Command               Mean +/- stddev       Maximum RSS (KiB)
>   diff -u expect actual  5.276 +/- 0.572 s              4199924
>   cmp expect actual      0.506 +/- 0.099 s                 1264
> 
> The test needs only an equality check. Use test_cmp_bin, which runs cmp,
> to compare the output byte for byte with less time and memory.

Yup, this is much more compelling as an argument now :)

Show 11 quoted lines

> diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
> index 4be5c51489..01b97c8888 100755
> --- a/t/t4205-log-pretty-formats.sh
> +++ b/t/t4205-log-pretty-formats.sh
> @@ -1189,7 +1189,7 @@ test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'set up huge commit' '
>  test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' '
>  	git log -1 --format="%B%<(1)%x30" $huge_commit >actual &&
>  	echo 0 >>expect &&
> -	test_cmp expect actual
> +	test_cmp_bin expect actual
>  '

And the patch looks obviously good to me.

Patrick