gdb hanging in emacs

Christopher Faylor
Sun Apr 29 22:19:00 GMT 2012

On Sun, Apr 29, 2012 at 08:53:24AM -0400, Ken Brown wrote:
>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?

There is nothing magical in the Cygwin gdb source.  Any recent gdb source
should be perfectly usable.


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