Re: [Boost-build] Finding the Boost root directory in sandbox libraries and within a Boost tree

Subject: Re: [Boost-build] Finding the Boost root directory in sandbox libraries and within a Boost tree
From: Gevorg Voskanyan (v_gevorg_at_[hidden])
Date: 2010-11-29 02:05:17

Edward Diener wrote:
> In my sandbox library I want to have a way that finds the Boost root directory  
>of an installation for my jamfiles, both when the end-user uses my jamfiles from  
>within the sandbox directory and also when the end-user moves my sandbox library  
>under a Boost tree.
> 
> I have been given two methods to do this, one by John  Maddock and one by 
>Daniel James, for a sandbox library, but I do not see how  either method will 
>work properly after the end-user moves my library under a  Boost tree.
> 
> In the method suggested by John Maddock, mentioned in the  sandbox readme.txt 
>file, the lines:
> 
> import modules ;
> local boost-path  = [ modules.peek : BOOST ] ;
> 
> are put in a jamfile and boost-path points  to the Boost root. But this 
>requires the end-use to either set the BOOST  environment variable to the boost 
>root directory or  specify
> 
> --boost=path
> 
> on the command line where path is the root of  a Boost tree. It also appears to 
>require the boost-build.jam in the sandbox  directory. I can not see how this 
>method is supposed to work once an end-user  moves my sandbox library under a 
>Boost tree since clearly the boost-build.jam is  different. I don't mind 
>instructing the end-user that they need to add  --boost=path to their bjam 
>invocations for my sandbox library wherever it is  placed, since this is much 
>more flexible than setting an environment variable,  but given that 
>boost-build.jam will be different in a Boost tree, I can not see  how this will 
>work there.
> 
> In the method suggested by Daniel James I  should use the jam file setup in the 
>sandbox 'example' library, with its  project-root.jam and its various jamfiles 
>at the project root level and at the  test and doc levels. But this requires the 
>BOOST_ROOT environment variable to be  set, which is something I doubt an 
>end-user is usually going to want to do when  they move the library under a 
>Boost root since it hardcodes a Boost root  location. If the end-user then wants 
>to use a sandbox library for a different  Boost tree, the BOOST_ROOT environment 
>would then need to be reset. Otherwise  this method seems fine so it seems the 
>best choice of the two.
> 
> Is there  any easier way that a sandbox directory can find the Boost root 
>without either  of these machinations, so that when the end-user tries to use 
>the jamfiles of a  sandbox library from within its sandbox directory, or moves 
>it under a Boost  tree, it sets a bjam local variable to the Boost tree root 
>correctly in either  case ? Perhaps I am asking for too much for a sandbox 
>library. Currently for my  sandbox library I am asking the end-user to move the 
>library under a Boost tree  in order to use it and hardcoding a local variable 
>to the Boost root of that  tree based on that, but I would rather do otherwise 
>especially as it should be  possible to try my sandbox library without having to 
>move it under a Boost tree.  I guess I am looking for a combination of Daniel 
>James' method and the ease of  use in John Maddock's method where a command-line 
>option points to the root of  the Boost tree since I feel that requiring the 
>end-user to set/change  environment variables seems  onerous.

What about referring to the boost project from within the sandbox libs as 
/boost, e.g. /boost//system, and having a Jamroot file in the root of sandbox 
containing
use-project /boost : /path/to/boost ;
line?
When a sandbox library gets moved inside an official Boost tree, it will 
continue to just work.

HTH,
Gevorg