Re: [Boost-build] Proposal to extend gcc's flavor feature

From: Vladimir Prus (ghost_at_[hidden])
Date: 2008-04-23 03:21:02

On Tuesday 22 April 2008 14:49:54 Roland Schwarz wrote:
> Vladimir Prus wrote:
> > You mean, even you you request second configured gcc explicitly,
> > you'll get the flavour of the first? That's a bug, and I think
> > the part of your patch that addresses that is OK.
> >
> >   
> I think this "unfortunatley" is not a bug, it just comes as a surprise 
> to the user. It seems
> to be a consequence of how default values are expanded.
> 
> E.g. the following definitions in user-config.jam
> 
> using gcc
>     : 3.4.2
>     : "C:/Programme/mingw-3.4.2/bin/g++.exe"
>     : <flavor>mingw
>       <root>"C:/Programme/mingw-3.4.2/"
>       <linkflags>-Wl,--enable-runtime-pseudo-reloc
>     ;
> 
> using gcc
>     : 3.4.4
>     : "c:/subsys/cygwin/bin/g++.exe"
>     : <root>"c:/subsys/cygwin/"
>     ;
> 
> and the following invocation:
> 
> bjam gcc-3.4.4
> 
> cause the correct compiler, i.e. c:/subsys/cygwin/bin/g++.exe being 
> called, but
> it gets a default flavor of mingw, which is not what was expected. This is
> because the flavor is only defined for mingw type gcc's.
> 
> My suggested fix will only work if _all_ compilers get a flavor during init.
> > 1. What additional information will be available that is not
> > available now? I presume, the real version?
> >
> >   
> I currently have 4 gcc's in use, the -dumpmachine gives:
> powerpc-linux                   a cross compiler
> i386-unknown-linux-gnu   the native compiler
> i686-pc-cygwin                gcc targeting cygwin dll's
> i686-pc-mingw32             the same gcc targeting msvc dll's
> mingw32                          the mingw (windows port) compiler
> 
> As you can see there is a lot of information, and what is more important, it
> is independant of what the user specifies in the version field.
> 
> Let assume the user specified, instead of my above definitions:
> 
> using gcc
>     : cgw
>     : "c:/subsys/cygwin/bin/g++.exe"
>     : <root>"c:/subsys/cygwin/"
>     ;
> 
> She would invoke as
> bjam gcc-cgw
> 
> and conditions the try to condition on <toolset-gcc:version>3.4.4 will 
> not trigger
> any more.

Do you think that adding compiler version to the flavour feature is a good thing?
That will make the 'flavour' feature fairly unstructured.
Should we have 'real-version' subfeature instead?

- Volodya