GDB hang on "run"

GDB hang on "run"

[Uri Moszkowicz]

Hi,
Lately gdb has been hanging for me when running my executable. I'm using
GDB 8.1 but it occurs with older versions as well. Here's what I see:

(gdb) source run.gdb
Temporary breakpoint 1 at 0xbaf645: file <path>/<file>.cc, line 3501.
^CTraceback (most recent call last):
  File "/<path>/gcc-6.2.0/redhat6/lib64/libstdc++.so.6.0.22-gdb.py", line
18, in <module>
    import gdb
ImportError: No module named gdb

What I see is a hang right before the Traceback message, that's only
bypassed by sending a SIGINT. Anyone know why this might be and what I can
do to avoid it? Or tips on how to debug this problem?

Thanks,
Uri

Re: GDB hang on "run"

[Tom Tromey]

>>>>> "Uri" == Uri Moszkowicz <uri@4refs.com> writes:

Uri> Lately gdb has been hanging for me when running my executable. I'm using
Uri> GDB 8.1 but it occurs with older versions as well. Here's what I see:

Uri> (gdb) source run.gdb
Uri> Temporary breakpoint 1 at 0xbaf645: file <path>/<file>.cc, line 3501.
Uri> ^CTraceback (most recent call last):
Uri>   File "/<path>/gcc-6.2.0/redhat6/lib64/libstdc++.so.6.0.22-gdb.py", line
Uri> 18, in <module>
Uri>     import gdb
Uri> ImportError: No module named gdb

Uri> What I see is a hang right before the Traceback message, that's only
Uri> bypassed by sending a SIGINT. Anyone know why this might be and what I can
Uri> do to avoid it? Or tips on how to debug this problem?

If your program uses a very large shared library, gdb might be reading
debug info for it.  Sometimes this can take a while and by default it
isn't announced.

Otherwise all I can suggest is attaching to gdb with another gdb,
interrupting it, and see what is going on.

If you suspect it is the "run" command itself, sometimes infrun logging
is interesting.  That is "set debug infrun 1".

Tom

Re: GDB hang on "run"

[Uri Moszkowicz]

Thanks for the tips. I was also noticing a hang exiting shells so I played
around a little bit and discovered that it's due to a Redhat6 NFS bug
around locking my .history file. I removed the file and the problem went
away.

On Wed, Aug 8, 2018 at 10:37 AM Tom Tromey <tom@tromey.com> wrote:

> >>>>> "Uri" == Uri Moszkowicz <uri@4refs.com> writes:
>
> Uri> Lately gdb has been hanging for me when running my executable. I'm
> using
> Uri> GDB 8.1 but it occurs with older versions as well. Here's what I see:
>
> Uri> (gdb) source run.gdb
> Uri> Temporary breakpoint 1 at 0xbaf645: file <path>/<file>.cc, line 3501.
> Uri> ^CTraceback (most recent call last):
> Uri>   File "/<path>/gcc-6.2.0/redhat6/lib64/libstdc++.so.6.0.22-gdb.py",
> line
> Uri> 18, in <module>
> Uri>     import gdb
> Uri> ImportError: No module named gdb
>
> Uri> What I see is a hang right before the Traceback message, that's only
> Uri> bypassed by sending a SIGINT. Anyone know why this might be and what
> I can
> Uri> do to avoid it? Or tips on how to debug this problem?
>
> If your program uses a very large shared library, gdb might be reading
> debug info for it.  Sometimes this can take a while and by default it
> isn't announced.
>
> Otherwise all I can suggest is attaching to gdb with another gdb,
> interrupting it, and see what is going on.
>
> If you suspect it is the "run" command itself, sometimes infrun logging
> is interesting.  That is "set debug infrun 1".
>
> Tom
>

Re: GDB hang on "run"

[Tom Tromey]

>>>>> "Uri" == Uri Moszkowicz <uri@4refs.com> writes:

Uri> Thanks for the tips. I was also noticing a hang exiting shells so I played
Uri> around a little bit and discovered that it's due to a Redhat6 NFS bug
Uri> around locking my .history file. I removed the file and the problem went
Uri> away.

Haha, that was definitely not on my list of possibilities :)

Tom