bug#21633: 25.0.50; assertion failure, self-insert-command with negative argument

[Nicolas Richard <youngfrog@members.fsf.org>]

Using the build mentionned below (i.e. built today) :

emacs -Q
Hit: C-- * (or C-- C-1 *)
=> crash (assertion failed)

Here's my gdb session, when setting a breakpoint :

Breakpoint 3, Fself_insert_command (n=9223372036854775807) at cmds.c:308
308	  CHECK_NUMBER (n);
(gdb) p n
$10 = 9223372036854775807
(gdb) xpr
Lisp_Int1
$11 = -1
(gdb) p CHECK_NUMBER (n)
$12 = void
(gdb) n
310	  if (XFASTINT (n) < 0)
(gdb) p XFASTINT (n)
$13 = 4611686018427387903
(gdb) xpr
Lisp_Misc
warning: value truncated
Cannot access memory at address 0xffffffff

At this point I realize I understand nothing about C and gdb. Anyway, I
say "next" and see that the above `if' statement failed to find the obvious
error :

(gdb) n
313	  if (XFASTINT (n) < 2)
(gdb) l
308	  CHECK_NUMBER (n);
309	
310	  if (XFASTINT (n) < 0)
311	    error ("Negative repetition argument %"pI"d", XFASTINT (n));
312	
313	  if (XFASTINT (n) < 2)
314	    remove_excessive_undo_boundaries ();
315	
316	  /* Barf if the key that invoked this was not a character.  */
317	  if (!CHARACTERP (last_command_event))
(gdb) 

Now I don't know what to do.

In GNU Emacs 25.0.50.2 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2015-10-06
Repository revision: 25b4572073179c8d6dc980ce2df3db4d96cd692f
Windowing system distributor 'The X.Org Foundation', version 11.0.11604000
System Description:	Gentoo Base System release 2.2

Configured using:
 'configure --with-x-toolkit=lucid --enable-checking --with-wide-int
 'CFLAGS= -O0 -g3''

Configured features:
XAW3D XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF
GSETTINGS NOTIFY ACL GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS LUCID X11

Important settings:
  value of $LANG: fr_FR.UTF-8
  locale-coding-system: utf-8-unix

-- 
Nicolas Richard