Re: [PATCH 2/2] builtin/mv: convert assert(3p) into `BUG()`

From: Junio C Hamano <gitster@pobox.com>
Date: Apr 30, 2025, 23:10 UTC
Message-ID: <xmqqecx9z1n6.fsf@gitster.g>
In-Reply-To: <xmqqr0191oaz.fsf@gitster.g>

Junio C Hamano <gitster@pobox.com> writes:

Show 19 quoted lines

> Patrick Steinhardt <ps@pks.im> writes:
>
>> The use of asserts is discouraged in our codebase because they lead to
>> different behaviour depending on how Git is built. When being unsure
>> enough whether a condition always holds so that one adds the assert,
>> then the assert should probably trigger regardless of how Git is being
>> built.
>
> Nicely put.  Yes, this is another reason why we frown on the use of
> assert(), in addition to the reason why why Elijah's series that
> ends with 5633aa3a (treewide: replace assert() with ASSERT() in
> special cases, 2025-03-19) was written.
>
>> Drop the call to assert(3p) in git-mv(1) and instead use `BUG()`.
>
> Being explicit about what we are unsure about is always good.  It
> would hopefully entice those who want to get their hands dirty to
> see if they can "prove" that BUG() would never happen, which would
> be a great outcome ;-).

By the way, with this in place, and without Dscho's "assert() makes Win+Meson test job get stuck, so let's make assert() a no-op" patch, the CI seems to be fine.

    https://github.com/git/git/actions/runs/14765572702

Triggering assert() and BUG() are something we would always want to notice. They should never trigger in production and it is an event to call for fixing the underlying cause that made the condition trigger if it is shown to end-users. Dscho's patch protects us from addition of a new test that triggers an assert(). We won't see such a test get stuck forever on Windows, but by turning such an assert() into a no-op, we would waste electricity for running CI only to miss the triggering assert(), which does not sound like a good use of our resources.

So I am inclined to drop Dscho's "build in release mode" patch when we merge this series down to 'next'. Being able to notice a breakage (which triggers a real assert(), whether it is due to broken code, or due to a broken test that documents a broken code path---which should be rewritten to use "if (condition) BUG()"), even if it needs to be done by noticing a test that gets stuck, would be much better than missing such a breakage at all, and that is the primary reasoning behind my suggesting to do so. I would not be surprised if I am missing a good reason or two to make build tested in CI ignore asserts, so let's hear from others.

Opinions?

Thanks.