Hello,

I'm using current stable on Ubuntu 15.10.

Steps to reproduce:
 - open emacs gdb-many-windows mode (I only hit this bug if the registers
buffer is open)
 - set a breakpoint
 - run

The following text appears in the gud window:
(gdb) Python Exception <class 'NameError'> name 'long' is not defined:
Python Exception <class 'NameError'> name 'long' is not defined:
Python Exception <class 'NameError'> name 'long' is not defined:
Python Exception <class 'NameError'> name 'long' is not defined:

Hitting enter reruns the program from the beginning.

-Doug
----
In GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.16.6)
 of 2015-09-17 on lgw01-52, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11702000
System Description:    Ubuntu 15.10

Configured using:
 `configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
 --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
 --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.5/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.5/site-lisp:/usr/share/emacs/site-lisp
 --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
 'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
 -Werror=format-security -Wall' CPPFLAGS=-D_FORTIFY_SOURCE=2
 'LDFLAGS=-Wl,-Bsymbolic-functions -Wl,-z,relro''

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Debugger

Minor modes in effect:
  gdb-many-windows: t
  shell-dirtrack-mode: t
  delete-selection-mode: t
  electric-pair-mode: t
  show-paren-mode: t
  electric-layout-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Making completion list...
Quit
Making completion list...
Complete, but not unique
Making completion list...
Complete, but not unique
~/dev/hw/cu/computer_systems/2_bomblab/bomb122
Target doesn't support non-stop mode.  Turning it off.
Gdb-Many-Windows mode enabled
Switched to thread 1
completing-read-default: Command attempted to use minibuffer while in
minibuffer

Load-path shadows:
/usr/share/emacs/24.5/site-lisp/debian-startup hides
/usr/share/emacs/site-lisp/debian-startup

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
help-fns mail-prsvr mail-utils thingatpt pcase vc-git ggtags etags
compile ewoc disp-table cc-langs cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs pcmpl-unix gdb-mi
bindat json gud easy-mmode init shell pcomplete comint ansi-color ring
delsel fill-column-indicator flycheck find-func help-mode rx subr-x seq
dash server exec-path-from-shell wombat-theme elec-pair cus-start
cus-load paren edmacro kmacro cl-loaddefs cl-lib saveplace ido info
easymenu package epg-config time-date tooltip electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd
fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 217848 73052)
 (symbols 48 29676 1)
 (miscs 40 285 586)
 (strings 32 56149 52692)
 (string-bytes 1 1626801)
 (vectors 16 28647)
 (vector-slots 8 1284058 121485)
 (floats 8 117 570)
 (intervals 56 830 86)
 (buffers 960 26)
 (heap 1024 71315 3522))