[boost] Strict or lax build configuration

Subject: [boost] Strict or lax build configuration
From: Vladimir Prus (vladimir_at_[hidden])
Date: 2009-11-16 04:56:45

I have a question how building Boost should behave when the user 
provides wrong configuration information. E.g., suppose you have this in 
user-config.jam:

        using python : 3.20 : /nowhere ;

or alternatively, in 1.42 a user runs Boost.Build as follows:

        ./bjam -sZLIB_INCLUDES=/still-nowhere ...

What should happen? 

- A hard error. After all, the user wanted that specific configuration. And
warnings are easy to miss.
- A warning. Autodetection will still run and possibly find a random version
- A hard error, but also run autodetection and let user know what was found.
  For example:

      Could not find Python version 3.20 in /nowhere.
      There is a valid installation of 2.5 in /usr.
      Remove the 'using python' statement to use it.

Comments?

Thanks,
Volodya