CVS Emacs Cygwin crash and browse-url question.

CVS Emacs Cygwin crash and browse-url question.

[Alex Bochannek]

Hello,

I have been trying to use CVS Emacs under Cygwin(*) for a while and had
experienced frequent SEGVs(**), which led me to stick with EmacsW32. I
tried to get it to run reliably again in my environment and finally
determined that the root cause of this problem is tool-bar-mode. It
seems to have something to do with a string object that has a bogus
address in it and the garbage collector trips over it. It's trivial to
reproduce(***) and even though I can live just fine without
tool-bar-mode I would be happy to help troubleshoot it.


CVS Emacs under Cygwin is working quite well for me now, but I noticed
that browse-url doesn't work. It seems odd to me that:

(defcustom browse-url-browser-function
  (cond
   ((memq system-type '(windows-nt ms-dos cygwin))
    'browse-url-default-windows-browser)
    ...

and

(defun browse-url-default-windows-browser (url &optional new-window)
  (interactive (browse-url-interactive-arg "URL: "))
  (if (eq system-type 'ms-dos)
      (if dos-windows-version
	  (shell-command (concat "start " (shell-quote-argument url)))
	(error "Browsing URLs is not supported on this system"))
    (w32-shell-execute "open" url)))

but obviously none of the w32 functions are included for the Cygwin
target.

I would like to be able to use the browser configured as default for
Windows and that's something that worked really well with EmacsW32 -
select a URL, a new tab opens up in Firefox. Obviously, I would rather
not run an additional browser under Cygwin and as useful as
text-browsers are for some content within an Emacs buffer, an external
Firefox is what works well for me.

I hope the observation regarding tool-bar-mode is useful and am looking
forward to suggestions on the browse-url issue.

Thanks,

Alex.


(*) GNU Emacs 22.0.97.1, X toolkit, Xaw3d scroll bars, CYGWIN_NT-5.1
    1.5.24(0.156/4/2), Microsoft Windows XP [Version 5.1.2600] SP1,
    AttachmateWRQ Reflection X 14.0.0.

(**) Program received signal SIGSEGV, Segmentation fault.
     0x200f204c in mark_object (arg=536990987) at alloc.c:5515
     5515            MARK_INTERVAL_TREE (ptr->intervals);

(**) emacs -q; C-h i; keep SPACE depressed until Emacs crashes

Re: CVS Emacs Cygwin crash and browse-url question.

[Eli Zaretskii]

> From: Alex Bochannek <alex@p9.com>
> Date: Thu, 12 Apr 2007 12:25:29 -0700
> 
> I have been trying to use CVS Emacs under Cygwin(*) for a while and had
> experienced frequent SEGVs(**), which led me to stick with EmacsW32. I
> tried to get it to run reliably again in my environment and finally
> determined that the root cause of this problem is tool-bar-mode. It
> seems to have something to do with a string object that has a bogus
> address in it and the garbage collector trips over it. It's trivial to
> reproduce(***) and even though I can live just fine without
> tool-bar-mode I would be happy to help troubleshoot it.

Thank you for your report.

First, please tell us whether the SEGVs happen even if you build the
Cygwin Emacs with the versions of GCC that are considered ``safe'' (in
the sense that other versions are known to produce a binary the
crashes almost instantly).  See the entry in PROBLEMS whose header is
"Building the Cygwin port for MS-Windows can fail with some GCC
version".  Also, please make sure you don't build the Cygwin port with
GTK+, as this configuration is known to crash on Cygwin (again, see
PROBLEMS).

If the crashes happen in a binary that is nether built with GTK+ nor
compiled by ``unsafe'' GCC versions, then yes, we would like to try to
debug this.  Unfortunately, none of the Emacs maintainers use Cygwin,
so all we can do is ask you to investigate and suggest ideas for how
to fix it.

Thanks.

Re: CVS Emacs Cygwin crash and browse-url question.

[Alex Bochannek]

Eli,

Eli Zaretskii <eliz@gnu.org> writes:

> First, please tell us whether the SEGVs happen even if you build the
> Cygwin Emacs with the versions of GCC that are considered ``safe'' (in
> the sense that other versions are known to produce a binary the
> crashes almost instantly).  See the entry in PROBLEMS whose header is
> "Building the Cygwin port for MS-Windows can fail with some GCC
> version".  Also, please make sure you don't build the Cygwin port with
> GTK+, as this configuration is known to crash on Cygwin (again, see
> PROBLEMS).

I used gcc (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125) as
provided by setup.exe. Eric's comment about what Setup provides is
correct and GCC 3.4.4 was only promoted in Cygwin from experimental to
current on 2006-09-25. I am in the process of building a GCC 4.1.2 for
Cygwin right now. I was aware of the GTK+ and Cygwin issues and didn't
even attempt to build that combination.


Finally, I was looking into the browse-url issue a bit more. I found
that using browse-url-firefox as the browse-url-browser function instead
of browse-url-default-windows-browser will correctly open a URL in a
Windows Firefox from a Cygwin Emacs when setting the
browse-url-firefox-program to the Cygwin path of the Windows
Firefox.

However, the way process-exit-status works when launching a Windows
program from Cygwin is different than expected and as a result the
process-sentinel will launch a second (tab in the running) Firefox. It
would be interesting to get the bottom of this.

Alex.

Re: CVS Emacs Cygwin crash and browse-url question.

[Alex Bochannek]

Eli Zaretskii <eliz@gnu.org> writes:

> If the crashes happen in a binary that is nether built with GTK+ nor
> compiled by ``unsafe'' GCC versions, then yes, we would like to try to
> debug this.  Unfortunately, none of the Emacs maintainers use Cygwin,
> so all we can do is ask you to investigate and suggest ideas for how
> to fix it.

Quick update: I have so far *not* been able to reproduce the crash with
CVS Emacs compiled with gcc (GCC) 4.1.2 under Cygwin.

Alex.

Re: CVS Emacs Cygwin crash and browse-url question.

[Eli Zaretskii]

> From: Alex Bochannek <alex@p9.com>
> Cc: emacs-devel@gnu.org
> Date: Fri, 13 Apr 2007 19:23:51 -0700
> 
> Quick update: I have so far *not* been able to reproduce the crash with
> CVS Emacs compiled with gcc (GCC) 4.1.2 under Cygwin.

Thanks.