Re: [boost] boost::random, header-only, boost::uuids::detail::seed_rng, and UWP development

Subject: Re: [boost] boost::random, header-only, boost::uuids::detail::seed_rng, and UWP development
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2017-09-12 14:39:12

On 09/12/17 15:40, James E. King, III via Boost wrote:
> Hi folks,
> 
> It looks like the only reason boostorg/random is not a header-only library
> is due to random_device (it is the only src/ file:
> https://github.com/boostorg/random/tree/develop/src). The older WinCrypt
> calls are not available in some Windows platforms going forward, so this is
> going to become a problem pretty quickly for the community.
> 
> In the boostorg/uuid library there is a seed_rng class which is doing
> similar things (however providing more entropy) and the library is
> header-only.  In addition there are two filed defects - one in Trac and one
> in github issues, about uuid being incompatible with UWP applications
> (that's Windows universal apps).  In uuid, I started adding support for
> BCrypt which is a Windows API supported on later versions of Windows, and
> once I changed my build flags to target Windows 10 and WINAPI_FAMILY_APP, I
> started getting build failures in random_device.
> 
> On further inspection it looks like the random library doesn't have support
> for BCrypt yet, and even worse as a source library one would need to build
> two variants - one for WinCrypt and one for BCrypt to support older and
> newer windows platforms.  There are also some implications on MinGW, as the
> older original MinGW has support for WinCrypt and MinGW-64 supports both.
> 
> I'm going to propose that the implementation from
> boost::uuids::detail::seed_rng be moved into boost::random as the new
> random_device implementation.  At the same time, boost::random will become
> header-only, and thus support setting _WIN32_WINNT at build time of
> consuming applications properly, and therefore support new Windows
> platforms properly.
> 
> At the same time I would like to change seed_rng such that it no longer
> silently ignores some return values, and does not disable any compiler
> warnings (deprecations, currently).
> 
> Thoughts?

I think that making Boost.Random header-only would be good.

In addition I would suggest adding support for getrandom() on Linux and 
getentropy() on OpenBSD, as they are protected from file descriptor 
exhaustion. This can be done in a separate PR though.

You will likely need to add BCrypt API to Boost.WinAPI - please, make a 
PR to it as well.