# Segmentation fault on auto-complete

My front-end freezes as soon as I type more than two letters in a notebook. I think the error occurs, when the auto-complete feature kicks in. If Mathematica was started from a terminal, the following text is shown.

Mathematica has received the signal: SIGSEGV and has exited.
If possible, please report this problem to support@wolfram.com
describing in as much detail as possible what you were doing
when the problem occurred.


I use Mathematica 10.3 on Ubuntu 12.04. Rebooting and -cleanstart did not help. This installation worked fine for quite some time, but suddenly this problem appeared.

Is this a known problem? Before I contact the official support, I want to make sure that there is no trivial fix.

• @StefanR You were right, CodeAssistHistory10.3.m was 321MB big! Removed it, everything works. Thanks! – murphy Mar 3 '16 at 19:25
• @murphy good to hear! Sorry you ran into this! – Stefan R Mar 3 '16 at 19:27
• @StefanR Maybe you should add your comment as an answer. That would make it more future-proof and I could close the question. – murphy Mar 5 '16 at 11:42
• I have just noted a similar behavior on 10.4 (Win 10 Pro), where all text inputs after two characters suddenly stopped as can bee seen in this capture of the problem. Unfortunately I was pointed to this post too late - I am just reinstalling Mathematica... – gwr Apr 18 '16 at 17:51
• See also this post asking for bug reports including the CodeAssistHistory files for better diagnostics of this problem and hopefully a fix in the future. – Emilio Pisanty Apr 24 '16 at 18:17

(Posting my comment as an answer, per @murphy's suggestion)

\$UserBaseDirectory/SystemFiles/FrontEnd/SystemResources/Functional‌​Frequency
and see if there are any unusually large files there (>100 Kb or so). If any such files exist, please delete them. The file CodeAssistHistory10.3.m is often the culprit, and is safe to delete.
• Are there plans to fix this? My CodeAssistHistory10.4.m is also huge (25.2 MB), and most of it is just a bunch of ÂÃÂÃ... – QuantumDot Apr 14 '16 at 13:07
• I can confirm that this solution works with regard to my above comment. My CodeAssistHistory10.4m had a size of 712 MB at the time of deletion. – gwr Apr 18 '16 at 18:58
• This didn't work for me. I didn't have any files of the form Code* in my FunctionalFrequency folder, and none of the files were over 18 MB. I deleted all the ones over 100 KB but the problem still persists if I enable autocomplete. – tparker May 17 '16 at 3:43