Hi, I'm one of the main authors of Browsix. One of our goals is to run C code - we have simple utilities from sbase running, and more complex code like latex and GNU make (the README needs updating). The main complication is that C code does system calls, which are traditionally blocking, and there isn't a good way to achieve that in current browsers with just ASM.js. So, we currently use the Emterpreter[1] (which is much slower) to make sure that anything on the stack underneath a system call can be saved and restored. SharedArrayBuffers should let us implement something faster in the near future.