Segmentation fault when reading CSV

[pelotom]

This looks like it might be a duplicate of #2167, but I want to verify that the fix for that also applies here. This file intermittently crashes R when attempting to fread it:

» Rscript -e "library(data.table); fread('bad.txt')"

 *** caught segfault ***
address 0x104463000, cause 'memory not mapped'

Traceback:
 1: fread("bad.txt")
An irrecoverable exception occurred. R is aborting now ...
Segmentation fault: 11

Interestingly, the size of the file seems to be related; it is 5 * 2^12 = 20480 characters in size, and if any characters are added or removed the error doesn't occur, but if characters are merely changed while keeping the total count the same, it still occurs.

[st-pasha]

This appears to be an instance of #2194
I verified that the crash occurs with fread from master branch, but doesn't occur with fread from branch "4kcrash".

[mattdowle]

Thanks Tom for reporting and for the file. Your bad.txt now added to the test suite.