Re: [PATCH 4/4] line-log: convert an assertion to a full BUG() call
- From
Johannes Schindelin <johannes.schindelin@gmx.de>
- Date
- Aug 6, 2018, 13:14 UTC
- Message-ID
- <nycvar.QRO.7.76.6.1808061510260.71@tvgsbejvaqbjf.bet>
- In-Reply-To
- <CAPig+cRrC2mf1uuQ1C4Ue4OMZQbgcxXbJ9AXs0y6RSnUrcm7Dg@mail.gmail.com>
Hi Eric,
On Sun, 5 Aug 2018, Eric Sunshine wrote:
Show 18 quoted lines
> On Sat, Aug 4, 2018 at 6:18 PM Johannes Schindelin via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> > The assertion in question really indicates a bug, when triggered, so we
> > might just as well use the sanctioned method to report it.
> >
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> > diff --git a/line-log.c b/line-log.c
> > @@ -72,7 +72,9 @@ void range_set_append(struct range_set *rs, long a, long b)
> > - assert(rs->nr == 0 || rs->ranges[rs->nr-1].end <= a);
> > + if (rs->nr > 0 && rs->ranges[rs->nr-1].end > a)
> > + BUG("append %ld-%ld, after %ld-%ld?!?", a, b,
> > + rs->ranges[rs->nr-1].start, rs->ranges[rs->nr-1].end);
>
> Although this appears to be a faithful translation of the assert() to
> BUG(), as mentioned by Andrei in his review of 3/4, the existing
> assert() seems to have an off-by-1 error, which means that the "> a"
> here really ought to be ">= a".I think Andrei's assessment is wrong. The code could not test for that earlier, as it did allow ranges to become "abutting" in the process, by failing to merge them. So the invariant you talked about is more of an invariant for the initial state.
My 3/4 would make that invariant heeded throughout the process.
I am still keen on keeping the invariants straight *without* resorting to dirty tricks like calling sort_and_merge. Calling that function would just make it easier for bugs to hide in this code.
> Given that this file is full of assert()'s, it doesn't necessarily > make sense to convert only this one, so perhaps the patch should be > dropped (since I'm guessing you don't want to convert the rest of > them).
Sure, there are 18 of them, and you're right, I lack the time to convert them.
Ciao, Dscho