"corrupted size vs. prev_size"

[Lars Ingebrigtsen <larsi@gnus.org>]

After the recent GIF/WebP caching changes, I sometimes get "corrupted
size vs. prev_size" and Emacs then hangs, so I guess I'm messing up
something in the memory allocation/freeing/writing bits somewhere.

But I'm getting it very, very rarely -- like one out of every thirty
times with a bunch of WebP/GIF images, so it's hard to track down.
Connecting to the hung Emacs isn't very informative:

(gdb) info threads
  Id   Target Id                                        Frame 
* 1    Thread 0x7f303a430000 (LWP 84136) "emacs"        0x00007f303d54e1f3 in __pselect (nfds=22, readfds=0x7ffd058d69e0, writefds=0x7ffd058d6a60, 
    exceptfds=0x0, timeout=0x7ffd058d6800, sigmask=<optimized out>)
    at ../sysdeps/unix/sysv/linux/pselect.c:52
  2    Thread 0x7f3039229640 (LWP 84137) "gmain"        0x00007f303d54b87f in __GI___poll (fds=0x561b63028870, nfds=2, timeout=-1)
    at ../sysdeps/unix/sysv/linux/poll.c:29
  3    Thread 0x7f303898c640 (LWP 84138) "gdbus"        0x00007f303d54b87f in __GI___poll (fds=0x561b63452d20, nfds=3, timeout=-1)
    at ../sysdeps/unix/sysv/linux/poll.c:29
  4    Thread 0x7f3033fff640 (LWP 84139) "dconf worker" 0x00007f303d54b87f in __GI___poll (fds=0x561b634be7d0, nfds=1, timeout=-1)
    at ../sysdeps/unix/sysv/linux/poll.c:29

I've stared at the code for some time now to see whether I can track the
problem down that way -- perhaps I've got some lifetime issues;
deallocating webp iterators twice, for instance, or something similar in
the gif code.  Does anybody else see something obviously wonky in that
code in gif_load or webp_load?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no