Re: Recent change in master breaks async package update using paradox

[Lars Brinkhoff]

Kaushal Modi wrote:
> Thanks a lot for the debug and fix. This was a tough bug to discover,
> especially when working with async. If you don't mind, and when you
> have time, can you please write about how you went about to debug this
> issue?

Well, half the credit should go to yourself for providing a good test
case for reproducing the problem.

Your backtrace pointed to the call to async-start in paradoc-execute.el.
The problem was knowing what happened in the subordinate Emacs.  I kind
of expected there to be some kind of debugging tool, so I keept my eyes
peeled for that.  Sure enough, there was async-debug.  First I only
turned it on in the parent Emacs and got some intersting info.  But the
breakthrough came when I turned it on also in the subordinate.  Then I
got the full backtrace pinpointing the location of the error.

It turned out that the error came from reading a huge string.  So it
still wasn't obvious what part of the string was wrong.  But it was just
a matter of removing substrings until only the one signalling an error
remained.