a few bjam questions (local/global , alias, and 'stage')

Dirk Griffioen wrote, on 9/2/2007 8:30 AM:
> Hi All,
>
> I have a few bjam questions - if anyone could give me
some pointers, 
> that would be very much appriciated ...

You should mention which version you're using.  That may
change the 
answer to some questions.  

> *1) local/global define*
>
> lib my_odbc
>   : [ obj a : a.cpp ]
>     [ obj b : b.cpp ]
>   :<define>ODBC
>   ;
>
> the define is not local so it is not used when
compiling, I dont like 
> having to set the define on both objs - is it possible
to set it once?

Well, first off, it's not clear from your example why you're
doing that 
instead of this:

    lib my_odbc : a.cpp b.cpp : <define>ODBC ;


It would behave the way you want that example to.  That
aside, there are 
a couple of options for this (that I know of).  You can use
a "project" 
target in that file like this:

    project my_odbc : requirements <define>ODBC ;

That would affect all targets in that jamfile and any
jamfiles mentioned 
via "use-project" (and maybe
"build-project"?).  Possibly also any 
jamfiles in sub-directories of that one.

Another way to do it would be with local variables:

    local defs = <define>ODBC ;
    lib my_odbc : [ obj a : a.cpp : $(defs) ] [ obj b :
b.cpp : $(defs)
    ] : $(defs) ;


The idea for the inline "obj" target is that you
want to compile one 
object differently than the other source files.  I think
they 
intentionally do not take build requirements from the
"lib" target, 
since they don't know what it is that you want to be
different.

> *2) alias*
>
> I have 2 targets that are 90% alike, the only
difference is they link 
> to 1 different library. Now I specify 2 targets which
are basically 
> copies. Is it possible to define a general target once
and specialize 
> it for the actual case:
>
> exe base : main.cpp lib-general ;
>
> alias exe-a  : base lib-a ;
> alias exe-b  : base lib-b ;
>
> At the moment base is compiled/linked, this fails
because some of the 
> symbols is in either lib_a or lib_b

I don't believe you can do that.  You should be able to do a
library 
that contains all the common sources and use it, though.  I
assume that 
the reason you want to do it like that is that there are
more sources 
(or libs) and/or requirements that you don't want to
repeat.

    lib exe-base : main.cpp lib-general ;
    exe exe-a : exe-base lib-a ;
    exe exe-b : exe-base lib-b ;


Another way you could do it:

    for local name in a b
    {
        exe exe-$(name) : main.cpp lib-general lib-$(name)
;
    }


> *3) os detection*
>
> The property <os>NT is defined, this is the only
value allowed. 
> However, I'd like
>
> exe my_exe : main.cpp : <os>NT
<define>GREAT ;
> exe my_exe : main.cpp : <os>LINUX
<define>BETTER ;
>
> Can I do this?

With the version I have, you can, which is why I said you
should tell us 
the version you're using.  The way you would do it, though,
would be:

exe my_exe : main.cpp : <os>NT:<define>GREAT
<os>LINUX:<define>BETTER ;

Note the colon (":") before the <define> and
that there can't be spaces 
around that colon.  See 
http://boost.org/doc/
html/bbv2/advanced.html#bbv2.advanced.targets.requirements.c
onditional

> *4) stage rename*
>
> I could'nt find this one:
>
> stage deliver : exe_a : <location>a
<rename>base ;
>
> In other words, I'd like to give a name to an install
target on 
> installation.

I can't help you with "stage" -- I always use
"install".  From my copy 
of stage.jam, it looks like you can use
"<name>" to rename it when you 
use the "install" target.

Phillip
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