bug#15575: 24.3.50; New tty menus crash Emacs

[Eli Zaretskii]

> From: Jan Djärv <jan.h.d@swipnet.se>
> Date: Thu, 10 Oct 2013 19:35:30 +0200
> Cc: 15575@debbugs.gnu.org
> 
> >  /* Count how many glyphs to copy and copy the glyphs.  */
> >  for (area = LEFT_MARGIN_AREA; area < LAST_AREA; ++area)
> >    for (i = 0; i < from->used[area]; i++)
> >      to->glyphs[area][i] = from->glyphs[area][i];  <<<<<<<<<<<<<<
> > 
> 
> It is the same place in the code, but not the same line in the file.
> 
> > then please tell what is the value of 'area' and of 'i' at the point
> > of the crash.
> > 
> 
> On Fedora 19:
> 
> (gdb) p area
> $1 = 1
> (gdb) p i
> $2 = 0
> (gdb) 
> 
> > Btw, did you compile with --enable-checking, i.e. were the 3 eassert
> > statements at the beginning of deep_copy_glyph_row compiled into the
> > program?
> 
> No, I did not.  I usually don't because the checkings more often than not 
> trip on something that really isn't a bug.  I've never caught a real error 
> with it.
> 
> This one triggers:
> 
> #3  0x0000000000449d2b in deep_copy_glyph_row (from=<optimized out>, 
>     to=0xce9e40) at /home/jhd/src/emacs/current/src/xdisp.c:20597
> 20597   eassert (to->used[0] == from->used[0]);
> 
> (gdb) p to->used[0]
> $1 = -15072
> 
> There is some memory corruption.  If I press F11 twice and then F10, the 
> crash does not happen. The menu appears but there are major redrawing 
> problems, for example, going down in the menu does not work, it just scrolls 
> the buffer instead until the menu disappears over the top, the buffer is not 
> redrawn correctly when the menu goes away, nor is the menu bar.  I did not 
> test it much.
> Could be another symptom of the memory corruption.

Can you please try the latest trunk (after reverting the patch you
applied on my request)?  I made some changes that perhaps could fix
this.

(I don't understand why the code worked for others on Fedora; are you
using a different development environment: compiler and/or library or
something?)