Message-ID: <4F9D39C4.4010904@cornell.edu>
Date: Sun, 29 Apr 2012 08:53:24 -0400
From: Ken Brown <kbrown AT cornell DOT edu>
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To: cygwin AT cygwin DOT com
Subject: Re: gdb hanging in emacs
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On 4/28/2012 3:58 PM, Ryan Johnson wrote:
> Hi all,
>
> I'm trying to use a home-built cross-gdb to do some remote debugging
> over tcp, but running gdb inside emacs doesn't work. M-x gud-gdb works
> fine, it's something wrong with the emacs integration. Unlike past times
> this has come up, the issue doesn't seem to be related to seg faults;
> the closest match I can find is from the emacs mailing list a while back
> [1], and involves a so-called "phase error." Basically, a large fraction
> of commands cause gud to hang in "[initializing...]" state for minutes
> or longer, apparently because it doesn't see what it expects and gets
> confused.
>
> The workaround to use 'file $BINARY' instead of specifying it at the
> command line avoids one problem, but simple things like 'set remotebaud
> 115200' also hang (unless added to a .gdbinit), and actually attempting
> to attach to the remote process similarly hangs forever in the
> initializing state. There is no CPU or disk utilization, and the command
> can't be interrupted with C-c C-c (though that does make it report a
> phase error before going back to hung). In some cases the "hang"
> resolves itself after about two minutes -- usually for simple commands
> like `set remotebaud' -- but more often than not, it's permanent. The
> behavior is also somewhat erratic, in the sense that the specific set of
> commands that hangs changes slowly over time and/or between invocations.
>
> So, two questions:
>
> 1. Has anyone else seen this, and if so, do they have any advice or
> workarounds?
>
> 2. Cygwin's official gdb doesn't seem to have any of these problems,
> though I can't test most of the commands, since it can't attach to the
> remote process. Is there some set of cygwin-specific patches I could
> borrow that make all the difference, or is my observation just coincidence?

Can't you just download the source for Cygwin's gdb and use that as the 
starting point for your home-built cross-gdb?

The only other thing I can suggest is that you try emacs-24, assuming 
you're currently using emacs-23.  emacs-24 uses a different method of 
invoking gdb (based on GDB/MI) than emacs-23, so it might conceivably 
work better.  If you want to try this, I can tell you off list how to 
get my build of the most recent pretest for emacs-24.1.

Ken

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