Confusing Mercurial history - was: Re: Hotspot segfaulting on Linux SPARC

[John Paul Adrian Glaubitz]

Hi Roman!

On 04/16/2018 08:36 PM, Roman Kennke wrote:
>> I would normally expect a changeset that was checked in in July to be included
>> in a revision that was checked in in August. I don't understand how one is supposed
>> to perform bi-secting with Mercurial if something as basic as a working history
>> doesn't work in Mercurial.
> 
> You're probably wrongly assuming that commit history is linear. It is
> not. TBH, I don't really know how hg bisect works with branchy history.
> It usually works fairly well in my experience. It will probably get
> confused if you start out with two revision on different branches? Or
> are you trying to bisect manually?

Yes, I am aware that the commit history is not linear. However, I am quite
sure that the revision 46931 previously contained the revisions 46667
and 46668 in the past but now it doesn't which is what confuses me.

> Here's some information around this stuff:
> http://hgbook.red-bean.com/read/finding-and-fixing-mistakes.html#sec:undo:bisect

I have found this guide as well and followed through it. However, in order
to start bisecting, I need to find a good revision first which is already
where I failed.

I tried many different revisions around 46931. But those either contained
the bug I am now seeing or they were missing various other changes which
are necessary to fix the build on linux-sparc.

I have successfully bisected large codebases like QEMU with git in the past
successfully but I am completely failing at that with Mercurial. I think
I will try a git mirror of the OpenJDK repository next because I am not
sure whether I am just using Mercurial wrong or whether bisecting there
is so much more difficult as compared to git.

For what is worth, I have also tried older versions of binutils and the
kernel to make sure that the crash that I am seeing on linux-sparc is
just not an artifact.

Adrian

-- 
  .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
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