Message-ID: <4F9C4BD1.1040401@cs.utoronto.ca>
Date: Sat, 28 Apr 2012 15:58:09 -0400
From: Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
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To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject: gdb hanging in emacs
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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?

Thanks!
Ryan

[1] http://lists.gnu.org/archive/html/help-gnu-emacs/2008-06/msg00713.html


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