Description: It looks like someone has changed the logic of the longest match in vim autocompletion. Now it tries to do the longest match after each new letter entered. And there are some ugly bugs which causes it to segfault the vim. Not mentioning that it's also very slow now. Looks like it calls omnifunc with every character entered.

Vim version: 7.3.289
Looks like it only appears when "set completeopt+=longest" is set.

Steps to reproduce: it's very easy to reproduce this bug with the option mentioned above + one of my omnifunc plugins: ccode (C/C++ completion based on clang) or gocode (Go completion). Both worked just fine with previous version of vim + the interaction with vim is minimal, therefore they shouldn't really cause a segfault by themselves.

Bug appears on both x86 and amd64.

I marked the severity as high, even though it's actually critical for people who use autocompletion a lot.