As I wanted to emerge app-doc/gimp-help, I wondered why my system was under very heavy load and it consumed almost all my memory. Then I found out it was because of convert from imagemagick, as it tried to convert a .png file:
convert -colors 128 dialogs-layer.png
After about 10 minuted, it stopped with a segfault. I did a little version bump on imagemagick. Now, the segfault is still there, but it doesn't consume that many resources anymore. I don't know where this bug comes from and it might be that one could use it for a buffer overflow attack. I will attach the .png file, so that you can check it out yourself.
*** This bug has been marked as a duplicate of 159567 ***