`std::random_device` can not constructing

[usagi]

Testing environment:

• Emscripten-1.20.0 ( with fastcomp )
• nodejs-0.10.25
• Ubuntu-14.04

Sample code:

#include <random>
#include <iostream>
#include <exception>

auto main()
  -> int
try
{
  std::random_device rd;
}
catch( const std::exception& e )
{
  std::cerr << e.what();
}

Result of the sample:

random_device failed to open /dev/urandom: No such file or directory

The exception thrown from maybe: https://github.com/kripken/emscripten/blob/master/system/lib/libcxx/random.cpp#L53

26.5.6 of the C++ specification:

A random_device uniform random number generator produces non-deterministic random numbers. If implementation limitations prevent generating non-deterministic random numbers, the implementation may employ a random number engine.

I think, Emscripten's std::random_device constructor is need specific token. Or, it need /dev/urandom emulation.

[kripken]

Probably /dev/urandom emulation is the best solution here.

[kripken]

Implemented.

[usagi]

@kripken

Thanks implement.

But, I think /dev/random and /dev/urandom need to be implemented by more safety random source if supported. I will write a patch and pull-request after in today.

( ref.: https://dvcs.w3.org/hg/webcrypto-api/raw-file/tip/spec/Overview.html#dfn-RandomSource )

[kripken]

Good point, yeah, we should use that where available.