Re: [jamboost] why repeated rule output?

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2002-04-01 22:09:47

Larry, have you read the Jam documentation and the supplementary
materials at
http://www.boost.org/tools/build/build_system.htm#jam_fundamentals? This
sort of thing is covered there.

If I invoke

jam always-target

It does indeed print "action output is ."

If you want always-target to be invoked even if you don't name it on the
command-line, add

DEPENDS all : always-target ;

-Dave

----- Original Message -----
From: "Larry Evans" <jcampbell3_at_[hidden]>
To: <jamboost_at_[hidden]>
Sent: Monday, April 01, 2002 9:57 PM
Subject: Re: [jamboost] why repeated rule output?

> Rene Rivera wrote:
>
> > On 2002-04-01 at 07:56 PM, jcampbell3_at_[hidden] (Larry Evans)
wrote:
> >
> > >The following top level Jamfile:
> > ><---------- top Jamfile -------------
> > >project-root
> > > ;
> > >
> > >rule test-rule
> > > {
> > > ECHO "rule output is" $(TOP) ;
> > > }
> > >
> > >test-rule
> > > ;
> >
>
> [snip]
>
> >
> > To resolve forward references in Jamfiles, they get included twice.
The first
> > time they don't generate build instructions (actions). The second
time they
> > do. To tell if it's the first pass you'r on do "if
$(gIN_LIB_INCLUDE)". The
> > name of the variable is historical :-\
> >
>
> Thanks much. I changed the Jamfile to:
> <-------------- new Jamefile ----------------
> project-root
> ;
>
> actions test-rule
> {
> echo "action output is" $(TOP)
> }
>
> rule test-rule
> {
> if ( ! $(gIN_LIB_INCLUDE) )
> {
> ECHO "rule output is" $(TOP) ;
> }
> }
>
> ALWAYS always-target
> ;
>
> test-rule always-target
> ;
> >---------------------------------------
> The output had just "rule output is ." and not the
> "action output is .". Do you have some idea why?
> TIA again.
>
>
>
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