Re: [Boost-users] Re: Are BOOST_BUILD_PATH && BOOST_ROOT necessary?

From: Steven T. Hatton (hattons_at_[hidden])
Date: 2004-09-03 21:05:19

On Friday 03 September 2004 12:06, David Abrahams wrote:
> "Steven T. Hatton" <hattons_at_[hidden]> writes:
> >From reading the documentation on boost.org, I have gotten the impression
> > I don't need to set $BOOST_BUILD_PATH and $BOOST_ROOT.
>
> Correct.

I've discovered BOOST_ROOT used in different places within the boost source 
tree.  I don't recall exactly where, but somewhere in the sourcetree there is 
a comment telling me that most of the builds will require that I have  
$BOOST_ROOT correctly set.  This is one place I found a reference to 
$BOOST_ROOT:

subproject libs/test/example ;

rule boost-test-example ( example-name : lib-name )
{
    exe $(example-name) : $(example-name).cpp <lib>../build/$(lib-name)
                        : <sysinclude>$(BOOST_ROOT) 
                          <stlport-iostream>on 
                          <borland><*><cxxflags>-w-8080 ;
}

Can I assume that is ignored if it isn't set?  

I just removed the user space install, and started with a fresh source tree 
from the tarball.  I have no boost related environment variable set.  I did 
find it necessary to:

export PYTHON_ROOT=/usr
export PYTHON_VERSION=2.3 

> It doesn't hurt for you to set BOOST_ROOT, as long as you set it
> accurately.  But you shouldn't need to.

Does it change the behavior of bjam to have it set?  I'm a bit confused 
regarding which bjam version is invoked by default.  The documentation 
suggests v1 will be invoke under certain conditions. All of my attempts to use 
the --v2 switch explicitly have resulted in a significant number of errors.  
That makes me thing the default is v1.

> > I'm using SuSE Linux 9.1 on a P4 box.  Some basic questions are these:
> >
> > When I downloaded and built boost, I first fetched the source for
> > bjam.
>
> Unneccessary, but it shouldn't hurt.  The bjam sources are in the
> tools/build/jam_src directory of your Boost installation.

What do you mean by "Boost installation"?  When I ran `bjam install' files 
were copied to 

/usr/local/include/boost-1_31/ # an acceptable location
and
/usr/local/lib # something I would never knowingly choose as a default

I manually coppied the bjam executable (which I also built from the 
boost-1_31_0 tarball.) to /usr/local/bin.  Beyond that, everything I got from 
the tarball still sits in the temporary directory I used for compilation.  I 
Shall I assume you mean to call that source tree, and the files produced by 
my running the script bjam build.sh and subsequent invocations of bjam, the 
"Boost installation"? 

This is certainly not consistent with the way the term installation is used 
with the gnu autotools.  Typically I would call the files placed in the 
--prefix directory the installation.  There's nothing wrong with using a 
different definition, so long as we are aware of what it means in the given 
context.

> > This is the name of the file I downloaded: boost-jam-3.1.10.tgz It
> > compiled quite nicely, and I copied the resulting bjam jam mkjambase
> > and yyacc to a location in my path.
>
> Why did you copy anything other than bjam?

I wasn't sure if the other executables might prove useful in the future.  
Since the script put four executables into the  bin.linuxx86/ where the bjam 
file was placed, I assumed all of these were intended for my use.

> > Are there necessary configuration file that I need to
> > have visible to these programs, even if they are not colocated?
>
> Not exactly.
>
> http://www.boost.org/tools/build/jam_src/#jambase_replacement

Ah yes, the source of much of my confusion:

"The Boost.Build v2 initialization behavior has been implemented. This 
behavior only applies when the executable being invoked is called "bjam" or, 
for backward-compatibility, when the BOOST_ROOT variable is set."

I'm not sure what that statement means.  In particular, what is meant by "this 
behavior"?  Does this mean the v2 behavior, or specifically the behavior 
described in the subsequent text?

"We attempt to load "boost-build.jam" by searching from the current invocation 
directory up to the root of the file-system. This file is expected to invoke 
the boost-build rule to indicate where the Boost.Build system files are, and 
to load them."

What are the "Boost.Build system files"?

"The boost-build rule adds its (optional) argument to the front of 
BOOST_BUILD_PATH, and attempts to load bootstrap.jam from those directories."

Is this bootstrap.jam for use when building my own projects, or only for use 
when building Boost libraries?  Typically bootstraps are used in the gnu 
world as a means of building the gcc compiler, or Emacs which needs to be 
able to compile its own Lisp.   They are not used after the first build, and 
do not become part of the installed package.

> describes the file that bjam expects to see when it starts up.  You
> might also drop a Jamrules file in the root directory of your own
> Boost.Build project (if you use bjam for your own project) that
> contains:
>
>   project boost : path/to/boost_1_31_0 ;

Does that mean the root of the directory structure of the tarball?

> Well, yeah, except that using the BOOST_ROOT directory for your
> --prefix is probably a bad idea.  I would leave the --prefix option
> off.

But that means everything is installed in the system's directory structure.  
That is not an ideal strategy for my purposes.  All other libraries and tools 
I have are installed in my own user space.

> > Is there anything else I need to do in order to compile my programs
> > against the boost headers and libraries?
>
> Add the include/ directory to your #include path and the lib/
> directory to your library search path?

By that am I to understand that when using the default installation my 
CPLUS_INCLUDE_PATH should contain /usr/local/include/boost-1_31  and my 
LIBRARY_PATH, and LD_LIBRARY_PATH should contain /usr/local/lib?

-- 
Regards,
Steven