From: Jonathan Nieder <jrnieder@gmail.com>
To: Jeff King <peff@peff.net>
Cc: Stefan Beller <sbeller@google.com>,
git@vger.kernel.org, git@jeffhostetler.com
Subject: Re: [PATCH 0/3] Introduce BUG_ON(cond, msg) MACRO
Date: Wed, 22 Nov 2017 16:08:39 -0800 [thread overview]
Message-ID: <20171123000839.GL11671@aiede.mtv.corp.google.com> (raw)
In-Reply-To: <20171122235851.GE8577@sigill>
Jeff King wrote:
> On Wed, Nov 22, 2017 at 03:45:32PM -0800, Jonathan Nieder wrote:
>> It lets you build with NDEBUG.
>
> But why do you want to build with NDEBUG if nothing uses assert()? ;)
No idea, but some distros (not Debian) have done it before and I don't
want to be burned again.
> I'm being a little glib, but I think there really is a chicken-and-egg
> question here. Why are people building with NDEBUG if they don't want to
> disable asserts?
It's because they want to disable asserts.
The semantics of assert is that they're allowed to be compiled out. A
person setting NDEBUG is perfectly within their rights to assume that
the author of a program has followed those semantics. Of course this
makes assert a terrible API from the point of view of Rusty Russel's
API rating scheme
<http://sweng.the-davies.net/Home/rustys-api-design-manifesto> but
it's what C gives us.
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.
[...]
>> It also goes through our own die()
>> handler, which means that e.g. the error message gets propagated over
>> remote transports.
>
> BUG() doesn't go through our die handler. It hits vreportf(), which does
> do some minor munging, but it always goes to stderr. Error message
> propagation over the remote protocol happens either:
>
> 1. From a parent process muxing our stderr onto the sideband.
>
> 2. Via special wrappers like receive-pack's rp_error().
>
> The only program I know that sets a custom die handler to change the
> reporting is git-http-backend (and there it only applies to die("BUG"),
> not BUG(), so with the latter you'd get a hard hangup instead of an
> attempt at an http 500).
Ah, interesting. That could be worth changing, though I don't think
it's too important.
[...]
> Yes, obviously side effects in an assert() are horrible. But I haven't
> noticed that being a problem in our code base.
>
> For the record, I'm totally fine with banning assert() in favor of a
> custom equivalent. I just don't think we've seen any real problems with
> assert in our codebase so far.
It sounds like we basically agree, then. :)
Jonathan
next prev parent reply other threads:[~2017-11-23 0:08 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 [this message]
2017-11-23 0:10 ` Jeff King
2017-11-23 1:38 ` Junio C Hamano
2017-11-23 5:00 ` Jeff King
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