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

Subject: Re: [Boost-build] Where in build are the OS names set
From: Vladimir Prus (ghost_at_[hidden])
Date: 2014-07-08 00:40:13

On 07/08/2014 04:00 AM, Edward Diener wrote:
> 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.

Edward,

these macros do not determine runtime environment, they determine compilation environment. See

        tools/build/src/engine/jam.h:89

> 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.

The problem is there are 3 variables:

        - The compiler that b2 was built with
        - The compiler that clang was built with
        - The execution environment - which is basically the shell where b2 is invoked (either cmd.exe or mingw's sh.exe)

For all I know, there's no strong correlation between those, so a way to explicitly specify how clang is build, or,
otherwise, a way for clang to report how it was build, will be necessary.

What does it even matter how clang was built?

- Volodya