Re: Merge of nickrob-async-20060513 to mainline?

[Nick Roberts <nickrob@snap.net.nz>]

Daniel Jacobowitz writes:
 > On Wed, Aug 30, 2006 at 02:25:01PM +1200, Nick Roberts wrote:
 > > 
 > > I have recently updated/merged the asynchronous branch (nickrob-async-20060513)
 > > that I am working on.  The overall task is too great for me to complete alone
 > > and it has attracted no interest as a branch.  For these reasons (and the
 > > coming release of Emacs 22) I would like to merge it with mainline GDB.  I have
 > > tried to arrange that GDB on my branch will only build with the "--async"
 > > option for GNU/Linux on i386.  This should mean that it should build and run as
 > > before on any other platform, and that itwill only run differently on
 > > i386-linux-gnu if the "--async" option is specified.
 > > 
 > > If it passes the current testsuite and I add some new testcases for the
 > > asynchronous operation (probably in the MI part of the testsuite), may I make
 > > such a merge?
 > 
 > Could you remind me what this has to do with the release of emacs 22?

In Emacs 22, interaction with gdb is done primarily with annotations (although
MI is accessed through "interprter-exec mi" for some features such as
variable objects.  After Emacs 22, the plan is to switch to MI but this
really requires asynchronous behaviour.

 > I'm not sure what interest you expected to generate on a branch, which
 > you didn't discuss on any of the mailing lists; as a rule, no one has
 > time to check out and poke at projects that no one tells them about.

I didn't really expect to generate much interest.  I thought I had discussed
it, although I haven't evangelised as it doesn't seem appropriate.
 
 > The last time I heard status from you on the branch, it wasn't working.
 > I gather it's better off now.  That makes it much more interesting.

I hadn't committed all the changes I had made until recently, so although
it wouldn't have worked, I had thought it would (at least in a limited way).

 > I think that merging it in without review would be at the least unwise.

If people are willing to review it then that is clearly preferable.  If
not, then after passing the testuite, putting it in the repository would
seem to be a good way to test it.  If it caused too much disruption then
it could be reverted fairy easily and there is plenty of time before the
next release.

 > How big are the changes relative to mainline (diffstat)?

A few extra files and a sprinkling of extra lines/if clauses (to test
if asynchronous) in twenty or so files.  I could run diffstat but I'm
not familiar with it.

 >                                                            Is there an
 > angle from which we can start looking at them?

Well, it should be invisible for anything but i386-linux-gnu and work as before
on i386-linux-gnu unless "--async" is specified.  To that extent it shouldn't
interfere with anyone not interested in using it.  However, I may used the
wrong files to try to achieve this.  There is also a file called README.async
in the branch.

Also it still uses pthreads.  You said previously that it should be done
in one process and, following a remark from Jim Ingham, that ptrace is
non-blocking.  AFAICS the problem is that wait *is* blocking and I can't
see of a way to deal with that without using another thread.

-- 
Nick                                           http://www.inet.net.nz/~nickrob