On 15.02.2017 11:25, Rene Rivera wrote:
>
>
> On Wed, Feb 15, 2017 at 10:23 AM, Stefan Seefeld via Boost-build

> <boost-build@lists.boost.org <mailto:boost-build@lists.boost.org>> wrote:
>
>     Hi Aaron,
>
>     On 15.02.2017 11:18, Aaron Boman via Boost-build wrote:
>     > The "using" rule is a convenience rule:
>     >
>     > using MODULE_NAME : field1 : field 2 : ... : field9 ;
>     >
>     > The above essentially does this:
>     >
>     > import MODULE_NAME ;
>     > MODULE_NAME.init field1 : field2 : ... : field9 ;
>     >
>     > So, if you look at the gcc.jam module, you'll notice that its init()
>     > rule's signature is this:
>     >
>     > rule init ( version ? : command * : options * )
>     >
>     > Thus, the using rule would be used like this:
>     >
>     > using gcc : $(valid-gcc-module-version-string) :
>     > $(optional-command-to-gcc-exe) : $(options) ;
>     >
>     > Where $(options) can be something like <root>root/directory or
>     > <flavor>mingw.
>     >
>     > You can find the using() rule's definition in the toolset module.
>
>     thanks, but I don't think that answers any of the questions.
>     Specifically, my last question was about the 'version' argument to the
>     gcc.init() function. Is it used to identify a compiler by version ? Or
>     can it be an arbitrary string / discriminator I use to configure
>     compilers with different flags (e.g. `--std=c++11` vs.
>     `--std=c++03`) ?
>
>
> For gcc it can be an arbitrary string.

How then does

using gcc : 6.3 ;
using gcc : 5.3 ;

work in practice ? How does b2 look up the appropriate compilers, if it
doesn't somehow match the version strings in the above snippet with the
output of `gcc --version` ?

> If I understand the python init code correctly, which is a challenge
> even for me, for python it must be the version of the interpreter (ie
> it checks that it matches).

OK. So for Python the proposed trick of using a "labeled version" to
name a specific Python instance unambiguously (e.g. in the presence of a
32-bit Python and a 64-bit Python of the same version) wouldn't work, yes ?