Re: msvc-stlport-tools patch

From: David Abrahams (dave_at_[hidden])
Date: 2003-12-23 10:38:54

"John Maddock" <john_at_[hidden]> writes:

>> > -flags msvc-stlport STLPORT_VERSION <stlport-version> ;
>> > +flags msvc-stlport STLPORT_VERSION_FLAG <stlport-version> : ;
>>
>> Sorry it took me so long to look at this. The change above looks
>> really suspicious to me. STLPORT_VERSION_FLAG isn't used anywhere
>> else in the toolset AFAICT.
>
> The thing is the original version trampled all over STLPORT_VERSION each
> time the toolset was invoked, resetting it to the default value each time.
> I'll be honest I don't actually understand why that line is in there
> -

The idea was for the version to be set "on" the target, so different
targets can be built with different STLPORT_VERSION settings. In
particular toolsets which extend this one should be able to do
something like 

{
local STLPORT_VERSION = ... ;
extends-toolset msvc-stlport
}

But it turns out that the line doesn't help, since STLPORT_VERSION
isn't used in the target's build actions.

> except that without it <stlport-version> gets ignored; as long as
> the macro name

Well, variable name. There aren't any macros in Jam. But yeah,
unless you set a variable with the feature using "flags", the feature
is marked "irrelevant" to the toolset and ignored. Another way would
be to use:

gRELEVANT_FEATURES($(gCURRENT_TOOLSET)) += <stlport-version>

but that's in no way superior.

> is something that's unused though it all works. If you have a better
> patch that's fine by me, but please make sure that STLPORT_VERSION is
> actually honored - as it is at present.

On second look your patch seems mostly fine. I'd suggest two changes:

local version ;
version ?= [ get-values <stlport-version> : $(gBUILD_PROPERTIES) ] ;
version ?= $(STLPORT_VERSION) ;

The first use of ?= doesn't make any sense; version is always empty
after you declare it local, so you might as well write:

local version = [ get-values <stlport-version> : $(gBUILD_PROPERTIES) ] ;
version ?= $(STLPORT_VERSION) ;

The other is to change STLPORT_VERSION_FLAG to something like
unused-flag-just-to-make-<stlport-version>-relevant .

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com