Re: [Boost-build] How to set proper scope in a generator rule?

From: Vladimir Prus (ghost_at_[hidden])
Date: 2006-02-14 03:36:39

On Tuesday 14 February 2006 01:44, Daniel Einspanjer wrote:
> I have a generator closely based upon the one Volodya described in his
> response to this thread:
> http://thread.gmane.org/gmane.comp.lib.boost.build/11654
>
> One of the things I did was make a rule with the same name as the action
> that builds up the variable XSL_TOOL which is used by the action.
>
> I discovered that I couldn't declare that variable as local in the rule
> because then the action couldn't see it.  What would be the proper way to
> scope that type of variable to reduce the possibility of collisions
> anywhere else?  Is it automatically scoped to the class? (I'm assuming it
> isn't because the rule and actions statements are outside the class
> definition.)

You mean you have

  rule whatever ( targets * : sources * : properties * )
  {
       .... XSL_TOOL = ....... ;
  }
  actions whatever
  {
       $(XSL_TOOL) ......
  }

Then, you can scope 'XSL_TOOL' on target, like this:

  rule whatever ( targets * : sources * : properties * )
  {
       XSL_TOOL on $(target[1]) = ....... ;
  }

This variable will be visible only inside the action. If the xsl command is 
the same for all actions, it might be easier to make it a global variable:

  rule init ( ............. )
  {
         XSL_TOOL = ........ ;
  }

If you need to handle more then one version of your xsl tool, you'd need more 
complex mechanism, something like:

  rule init ( version : command )
  {
                flags your-module.whatever XSL_TOOL <xsl-tool-version>$(version) 
           : $(command) ;
  }

- Volodya