GHC HEAD (Quickest) segfaults during compilation of optparse-applicative

Ömer Sinan Ağacan omeragacan at
Tue Mar 10 12:18:32 UTC 2020

Can you file a bug report please with reproduction instructions? I know of one
heap corruption bug (#17785, I'm currently debugging it) but it's impossible to
tell whether this is the same bug or not just by looking at your screenshot.

In practice whether they're the same bug or not is quote hard to answer, and it
also does not matter too much, for several reasons:

- Segfaults/heap corruption usually happens as a result of interaction of many
  different features and code so usually it's impossible to tell, just by
  looking at the reproducer, what is responsible.

- It's usually a good idea to debug different reproducers at the same time. If
  they're caused by the same problem then one of the reproducer may lead to the
  bug faster/easier than others so it's a good idea to explore them in parallel.

  If they're caused by different bugs then exploring all in parallel does not
  cause any extra work (unless you're context switching at a high rate, which I
  usually avoid).

- More reproducers = more tests, which are good.

Also, when you ask whether this is a known bug on the mailing list it's
effectively the same as just submitting a bug report: either way you don't
search it yourself and ask for other devs to do it.



Csaba Hruska <csaba.hruska at>, 10 Mar 2020 Sal, 15:08
tarihinde şunu yazdı:
> I've created a bug sample project on github:
> Follow the readme to reproduce the bug.
> Cheers,
> Csaba
> On Tue, Mar 10, 2020 at 12:31 PM Csaba Hruska <csaba.hruska at> wrote:
>> Hello,
>> GHC HEAD (9668781a36941e7552fcec38f6d4e1d5ec3ef6d1) compiled with the Quickest flavour segfaults when compiles optparse-applicative-
>> But it compiles fine with the Quick or the default flavours.
>> Everything compiles fine (with vanilla Quickest GHC HEAD) until the Options.Applicative.Help.Core module where GHC segfaults. (as I understand the error code)
>> Is this a known bug?
>> If not then I'll submit an issue.
>> Thanks,
>> Csaba
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