Re: [Boost-build] How can I pass vars to actions

Subject: Re: [Boost-build] How can I pass vars to actions
From: Jose . (kasty.jose_at_[hidden])
Date: 2014-03-20 15:26:35

It works!!!  Just to summarize, this is the complete code:

import feature : feature ;
feature message : : free ;

rule myecho ( targets * : sources  * : properties * )
{
    _MSG on $(targets) = [ feature.get-values <message> : $(properties) ] ;
}
actions myecho
{
    echo "MSG = $(_MSG)" ;
}

make Hola : : @myecho : <message>Hola ;
make Adios : : @myecho : <message>Adios ;

Thanks.

2014-03-20 19:57 GMT+01:00 Steven Watanabe <watanabesj_at_[hidden]>:

> AMDG
>
> On 03/20/2014 11:10 AM, Jose . wrote:
> > I read the BBv2 documentation and samples. I don't want to create my own
> > generator, just to see "Hola" "Adios" as the output of this program:
> >
> > rule myecho
> > {
> >     _MSG on $(<) = $(MSG) ;
> > }
> > actions myecho bind _MSG
> > {
> >     echo "MSG = $(_MSG)" ;
> > }
> >
>
> Note: bind _MSG means that $(_MSG) is a target
> and you want the name of the file, rather than
> the internal name.  It doesn't really make sense
> in this example.
>
> > constant MSG : "hola" ;
> > make Hola : : @myecho ;
> >
> > constant MSG : "adios" ;
> > make Adios : : @myecho ;
> >
> > Why I only see "adios" "adios" ? I guess it's because the variable inside
> > the action is not evaluated until the action executes. But the rule
> myecho
> > should be executed in the first pass, hence _MSG should contain "Hola"
> for
> > target Hola, and "Adios" for target Adios.
> >
> > Am I missing anything?
>
> Yes.  Boost.Build doesn't make two passes.  It makes three.
> 1) Parse Jamfiles
> 2) Generate actual targets
> 3) Run updating actions
>
> (This should make sense if you keep in mind that a
> target in the Jamfile can end up creating several
> actual targets for debug and release builds, static
> vs. shared libraries, different compilers, etc.)
>
> the rules are run in step 2 after MSG has already been
> set to "adios".
>
> > How can I pass a different message to a Make rule
> > depending on the target? Can I avoid creating a generator?
> >
>
> This is what features (e.g. cxxflags) are for.
>
> import feature : feature ;
> feature message : : free ;
>
> rule myecho ( targets * : sources * : properties * )
> {
>   _MSG on $(targets) =
>     [ feature.get-values <message> : $(properties) ] ;
> }
>
> make adios : : @myecho : <message>adios ;
>
> In Christ,
> Steven Watanabe
>
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