[Boost-build] Where in build are the OS names set

Subject: [Boost-build] Where in build are the OS names set
From: Edward Diener (eldiener_at_[hidden])
Date: 2014-07-07 20:00:59

Where in Boost Build are the various OS names set that I see mentioned 
in builtin.jam in the default-host-os local rule ( and a few other 
places ) ?

I see such OS names as NT, MACOSX, LINUX etc. I am particularly 
interested in how the OS is determined in Boost Build. One of the OS 
names is MINGW and I am interested to know how Boost Build determines 
that the environment in which it is being used is MINGW under Windows.

In trying to work out a solution for determining whether or not an 
invocation of clang under Windows is using clang as built using MingW or 
clang as built using VC++ the OS name of MINGW might be used to 
distinguish between them if I can understand how it is determined. The 
only alternative I can think of is that the end-user must specify a 
command which invokes clang-cl for VC++, otherwise it is clang as built 
using MingW, but I would like to avoid this added burden on the end-user 
if necessary when using clang under Windows.