[boost] Re: boost jam questions

From: David Abrahams (dave_at_[hidden])
Date: 2003-05-15 13:49:59

Trevor Taylor <xju_at_[hidden]> writes:

> Hi,
>
> I set out to use Boost Jam to build my latest little experiment. I
> have some questions/comments:
>
> Why does it build everything into a target-specific subdirectory?
> ----------------------------------------------------------------

Because targets may have different property requirements, and that was
the easiest way to avoid clashes.  Boost.Build v2 is much smarter
about avoiding that when possible.

> I have lots of classes and tests and tend to build up my Jamfile to
> reflect their inter-dependencies, e.g.
>
>      a.cc =
>         a.cc
>         $(b.cc) ;
>
>      c.cc =
>         a.cc
>         $(b.cc) ;
>
>      b.cc = b.cc ;
>
>      exe a : $(a.cc) ....
>      exe c : $(c.cc)
>
> But building a and c compiles c.cc twice (once into
> bin/a.exe/gcc/debug/runtime-link-dynamic/b.o and once into
> bin/c.exe/gcc/debug/runtime-link-dynamic/b.o

All I can suggest is that you build intermediate libraries.

> I would have thought bin/gcc/debug/b.o would have been enough. Why
> would the b.o produced depend on which executable it was bound for?

Because a might be built with one set of requirements (say,
<rtti>off) and b with another.

> Why would it depend on wether it was bound for a dll or not?
>
> I modified my boost/tools/build/boost-base.jam to at least remove the
> a.exe level so I didn't spend all night watching the compiler.
>
> Where are "compile and link flag" equivalents documented?
> --------------------------------------------------------
>
> I wanted to link against libxerces.a that I had built separately, but
> couldn't figure out how to specify the equivalent of -L/blah -lxerces.

I'm afraid they're not documented.  You should add:

    <library-path>/blah

and

    <find-library>xerces

to your executable's requirements.

> How does one add a rule for building C++ files from e.g. IDL?
> -------------------------------------------------------------
>
> In my case I am using Qt which needs me to run its "moc" compiler to
> generate a .cc from my .hh. I put in:
>
> 	rule moc
> 	{
> 	   DEPENDS $(<) : $(>) ;
> 	}
> 	actions moc
> 	{
> 	   "$(QTDIR)/bin/moc.exe" "-o" $(1) $(2)
> 	}
>
> 	moc mTasks.cc : Tasks.hh ;
>
> But somehow that resulted in either Boost Jam looking for something
> like bin/a.exe/gcc.../Tasks.hh or insisting on recompiling mTasks.cc
> everytime (bjam -d output suggested Tasks.hh didn't exist, when
> clearly it did).

I think Vladimir already answered this one, to some extent.  We have
it in BBv2.

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