Re: [jamboost] Perforce Jam incompatibility

From: Rene Rivera (grafik666_at_[hidden])
Date: 2002-11-16 01:37:15

[2002-11-15] David Abrahams wrote:

>
>I was just looking over Rene's new document at
>http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/*checkout*/boost/boost/tools/build/jam_src/readme.html,
>which says,
>
> "It contains significant improvements made to facilitate its use in
> the Boost Build System, but should be backward compatible with
> Perforce Jam"
>
>Well, we have one known backwards(?)-incompatibility:
>
>When Perforce introduced rule indirection, they did it a bit
>differently than we did:
>
> x = a b ;
> y = [ $(x) c d ] ;
>
>In Boost.Jam, this is equivalent to:
>
> y = [ a b c d ] ;

Logical.

>In Perforce Jam, this is equivalent to:
>
> a c d ;
> y = [ b c d ] ;

Yikes, how unintuitive.

>Either behavior can be built in terms of the other, but I thought the
>Boost.Jam behavior was more-useful, and we were there first, so I
>didn't change it when Perforce added rule indirection. I don't know if
>that was a bad choice. However, we ought to decide whether to keep
>that difference, and if so, how to document it.

Is there any way to support both? That is can we decide at runtime which one
to use, for instance by using the bjam vs jam invocation? Perhaps a builtin,
like Vladimir did with the UPDATE to make up for removing the command args
functionality.

I'm curious because I think having that compatability with Jam/MR might be
important when we put back in the 2.4 Jambase.

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