From: Junio C Hamano <gitster@pobox.com>
To: Jonathan Nieder <jrnieder@gmail.com>
Cc: Jeff King <peff@peff.net>, Stefan Beller <sbeller@google.com>,
git@vger.kernel.org, git@jeffhostetler.com
Subject: Re: [PATCH 0/3] Introduce BUG_ON(cond, msg) MACRO
Date: Thu, 23 Nov 2017 10:38:07 +0900 [thread overview]
Message-ID: <xmqqefopsrk0.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20171123000839.GL11671@aiede.mtv.corp.google.com> (Jonathan Nieder's message of "Wed, 22 Nov 2017 16:08:39 -0800")
Jonathan Nieder <jrnieder@gmail.com> writes:
> FWIW I think we've done fine at using assert so far. But if I
> understand correctly, the point of this series is to stop having to
> worry about it.
I recalled that there was at least one, and "log -Sassert" piped to
"less" that looks for "/^[ ^I]*assert\(" caught me one recent one.
08414938 ("mailinfo.c: move side-effects outside of assert", 2016-12-19)
Even though I do not personally mind
assert(flags & EXPECTED_BIT);
assert(remaining_doshes == 0);
left as a reminder primarily for coders, we can do just as well do
so with
if (remaining_doshes != 0)
BUG("the gostak did not distim all doshes???");
So I am fine if we want to move to reduce the use of assert()s or
get rid of them. I personally prefer (like Peff, if I am not
mistaken) an explicit use of the usual control structure, as it is
easy to follow. BUG_ON() would become another thing readers need to
get used to, if we were to use it, and my gut feeling is that it may
not be worth it.
A few more random things related to this topic that comes to my
mind:
- If we had a good set of tools to tell us if an expression is free
of side-effects, then assert(<expression>) would be less
problematic---we could mechanically check if an assert() that is
left as a reminder for coders/readers is safe.
- Even if we had such a check, using the check only on new changes
when a patch is accepted is not good enough. An assert(distim())
may have been safe back when it was added because distim() used
to be free of side-effects, but a later update to it may add side
effects to it.
- The issue that is caused by "this function used to be pure but
lately it gained side-effects" is not limited to assert(). Using
it in "if (condition) BUG(...)" or "BUG_ON(condition,...)" will
not sidestep the fact that such a change will alter behaviour of
callers of the function. It's just that assert(condition) is
conditionally compiled, which makes the issue a worse one.
next prev parent reply other threads:[~2017-11-23 1:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-22 22:38 [PATCH 0/3] Introduce BUG_ON(cond, msg) MACRO Stefan Beller
2017-11-22 22:38 ` [PATCH 1/3] Documentation/CodingGuidelines: explain why assert is bad Stefan Beller
2017-11-22 22:59 ` Jonathan Nieder
2017-11-22 23:08 ` Stefan Beller
2017-11-22 23:54 ` Jonathan Nieder
2017-11-22 22:38 ` [PATCH 2/3] git-compat: introduce BUG_ON(condition, fmt, ...) macro Stefan Beller
2017-11-22 23:02 ` Jonathan Nieder
2017-11-22 23:37 ` Jeff King
2017-11-22 22:38 ` [PATCH 3/3] contrib/coccinelle: convert all conditional bugs to bug_on Stefan Beller
2017-11-22 23:24 ` [PATCH 0/3] Introduce BUG_ON(cond, msg) MACRO Jeff King
2017-11-22 23:28 ` Jonathan Nieder
2017-11-22 23:39 ` Jeff King
2017-11-22 23:45 ` Jonathan Nieder
2017-11-22 23:58 ` Jeff King
2017-11-23 0:08 ` Jonathan Nieder
2017-11-23 0:10 ` Jeff King
2017-11-23 1:38 ` Junio C Hamano [this message]
2017-11-23 5:00 ` Jeff King
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