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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: Jonathan Tan <jonathantanmy@google.com>
Cc: git@vger.kernel.org, peff@peff.net, stolee@gmail.com,
	gitster@pobox.com, jeffhost@microsoft.com
Subject: Re: [PATCH v2] usage: trace2 BUG() invocations
Date: Sat, 27 Mar 2021 18:56:49 +0100	[thread overview]
Message-ID: <87mtuoo4ym.fsf@evledraar.gmail.com> (raw)
In-Reply-To: <20210205200908.805639-1-jonathantanmy@google.com>


On Fri, Feb 05 2021, Jonathan Tan wrote:

> die() messages are traced in trace2, but BUG() messages are not. Anyone
> tracking die() messages would have even more reason to track BUG().
> Therefore, write to trace2 when BUG() is invoked.
> [...]
> +# Verb 007bug
> +#
> +# Check that BUG writes to trace2
> +
> +test_expect_success 'normal stream, exit code 1' '
> +	test_when_finished "rm trace.normal actual expect" &&
> +	test_must_fail env GIT_TRACE2="$(pwd)/trace.normal" test-tool trace2 007bug &&
> +	perl "$TEST_DIRECTORY/t0210/scrub_normal.perl" <trace.normal >actual &&
> +	cat >expect <<-EOF &&
> +		version $V
> +		start _EXE_ trace2 007bug
> +		cmd_name trace2 (trace2)
> +		error the bug message
> +		exit elapsed:_TIME_ code:99
> +		atexit elapsed:_TIME_ code:99
> +	EOF
> +	test_cmp expect actual
> +'
> +
>  sane_unset GIT_TRACE2_BRIEF
>  
>  # Now test without environment variables and get all Trace2 settings
> diff --git a/usage.c b/usage.c
> index 1868a24f7a..1b206de36d 100644
> --- a/usage.c
> +++ b/usage.c
> @@ -266,6 +266,10 @@ int BUG_exit_code;
>  static NORETURN void BUG_vfl(const char *file, int line, const char *fmt, va_list params)
>  {
>  	char prefix[256];
> +	va_list params_copy;
> +	static int in_bug;
> +
> +	va_copy(params_copy, params);
>  
>  	/* truncation via snprintf is OK here */
>  	if (file)
> @@ -274,6 +278,13 @@ static NORETURN void BUG_vfl(const char *file, int line, const char *fmt, va_lis
>  		snprintf(prefix, sizeof(prefix), "BUG: ");
>  
>  	vreportf(prefix, fmt, params);
> +
> +	if (in_bug)
> +		abort();
> +	in_bug = 1;
> +
> +	trace2_cmd_error_va(fmt, params_copy);
> +
>  	if (BUG_exit_code)
>  		exit(BUG_exit_code);
>  	abort();

I see it's an existing bug/misfeature of this whole part of trace2 that
error()/warning()/usage() etc. don't pass down the file and line number
of their callers. We'd need to make all of those functions a macro for
that to work.

But it can work for BUG(), since we have the file/line parameters
there. Any reason that's not passed down to trace2 in this case, instead
of calling trace2_cmd_error_va() which'll lose that information?

I.e. if you change your test to use GIT_TRACE2_EVENT you'll see that you
get an event like:

    {"event":"error"[...]"file":"usage.c","line":308,
    "msg":"the bug message","fmt":"the bug message"}

It seems that currently the only way to tell these error events apart
now is to hardcode those known usage.c line numbers on the consumer
side, unless I'm missing something.

      parent reply	other threads:[~2021-03-27 17:57 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05  5:49 [PATCH] usage: trace2 BUG() invocations Jonathan Tan
2021-02-05  6:17 ` Junio C Hamano
2021-02-05  9:01   ` Jeff King
2021-02-05 12:51     ` Derrick Stolee
2021-02-05 13:44       ` Jeff King
2021-02-05 16:34       ` Jeff Hostetler
2021-02-05 20:09 ` [PATCH v2] " Jonathan Tan
2021-02-09 12:03   ` Jeff King
2021-02-09 19:34     ` Jonathan Tan
2021-02-09 21:18       ` Junio C Hamano
2021-02-09 22:15       ` Junio C Hamano
2021-03-27 17:56   ` Ævar Arnfjörð Bjarmason [this message]

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