Re: [PATCH 2/3] test-lib: simplify lsan results check

From: Patrick Steinhardt <ps@pks.im>
Date: Jan 7, 2025, 07:37 UTC
Message-ID: <Z3zZt2OCjcDGvjBS@pks.im>
In-Reply-To: <20250107070752.GB584668@coredump.intra.peff.net>

On Tue, Jan 07, 2025 at 02:07:52AM -0500, Jeff King wrote:

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> We want to know if there are any leaks logged by LSan in the results
> directory, so we run "find" on the containing directory and pipe it to
> xargs. We can accomplish the same thing by just globbing in the shell
> and passing the result to grep, which has a few advantages:
> 
>   - it's one fewer process to run
> 
>   - we can glob on the TEST_RESULTS_SAN_FILE pattern, which is what we
>     checked at the beginning of the function, and is the same glob use

s/use/used

I'm always a bit thrown off by your style of bulleted lists, where they feel like sentences but start with a lower-case letter, and sometimes they do and sometimes they don't end with punctuation. Maybe it's just me not being a native speaker and it's a natural thing to do in English. In any case, it's nothing that really matters in the end, but would be happy to learn if this is indeed something you tend to do in English.

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>     to show the logs in check_test_results_san_file_
> 
>   - this correctly handles the case where TEST_OUTPUT_DIRECTORY has a
>     space in it. For example doing:
> 
>        mkdir "/tmp/foo bar"
>        TEST_OUTPUT_DIRECTORY="/tmp/foo bar" make SANITIZE=leak test
> 
>     would yield a lot of:
> 
>       grep: /tmp/foo: No such file or directory
>       grep: bar/test-results/t0006-date.leak/trace.test-tool.582311: No such file or directory
> 
>     when there are leaks. We could do the same thing with "xargs
>     --null", but that isn't portable.
> 
> We are now subject to command-line length limits, but that is also true
> of the globbing cat used to show the logs themselves. This hasn't been a
> problem in practice.

Yup, this also came to my mind immediately. But I agree that it shouldn't be an issue in general.

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> We do need to use "grep -s" for the case that the glob does not expand
> (i.e., there are not any log files at all). This option is in POSIX, and
> has been used in t7407 for several years without anybody complaining.
> This also also naturally handles the case where the surrounding
> directory has already been removed (in which case there are likewise no
> files!), dropping the need to comment about it.

Okay. So in case there are no matching files we don't expand the globbing string, and "--no-messages" makes us ignore that case. A bit funny, but I don't see any issue with it.

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> Signed-off-by: Jeff King <peff@peff.net>
> ---
> I was surprised by the use of "grep -s" in t7407, since it is totally
> pointless there. But I think we can take its presence as a positive sign
> for portability.

Good to know.

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>  t/test-lib.sh | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index be3553e40e..898c2267b8 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1172,12 +1172,7 @@ test_atexit_handler () {
>  check_test_results_san_file_has_entries_ () {
>  	test -z "$TEST_RESULTS_SAN_FILE" && return 1
>  
> -	# stderr piped to /dev/null because the directory may have
> -	# been "rmdir"'d already.
> -	find "$TEST_RESULTS_SAN_DIR" \
> -		-type f \
> -		-name "$TEST_RESULTS_SAN_FILE_PFX.*" 2>/dev/null |
> -	xargs grep ^DEDUP_TOKEN |
> +	grep -s ^DEDUP_TOKEN "$TEST_RESULTS_SAN_FILE".* |
>  	grep -qv sanitizer::GetThreadStackTopAndBottom

And this nicely simplifies things indeed.

Patrick