System Information
MacBook Pro

Processor Name:	Intel Core i7
Processor Speed:	2,2 GHz
Number of Processors:	1
Total Number of Cores:	4
L2 Cache (per Core):	256 KB
L3 Cache:	6 MB
Memory:	16 GB
Chipset Model:	Intel Iris Pro
Type:	GPU
Bus:	Built-In
VRAM (Dynamic, Max):	1536 MB

OS El Capitan
v: 10.11.6

Blender Version
2.79b

Short description of error
Trying to use the "C" shortcut to paint select simply freezes Blender and needs to restart - no option to save. (btw. how about having the closing dialogue box offering review changes in such cases?)

Exact steps for others to reproduce the error
Go to UV editor after unwrapping. Hit the C-key and voila