Default build improvement

From: Vladimir Prus (ghost_at_[hidden])
Date: 2003-03-07 05:28:26

I've just comitted a quite small (textually), but important change.

Suppose you have 

exe a : a.cpp : : debug release ;

("debug release" is default-build). Previously, both version would be
built if you run "bjam", but only one is you run "bjam gcc" or 
"bjam optimization=space". Now, build request and default-build are
combined.

One practical consequence: if top-level default-build include 
"<stdlib>stlport", this property will be used always, unless you
explicitly override it. E.g. no need to type 

bjam debug stdlib=stlport threading=multi

when all you want to change from release to debug build.

However, there's one use case I'm not sure about:

d1/Jamfile reads

exe main : main.cpp ../d2/l ;

d2/Jamfile reads:

lib l : l.cpp : : <optimization>space ;

The intention is to build "l" with space optimization, unless asked otherwise.
Is this important use case? And what to do in this case:

lib l : l.cpp : : <rtti>off ;

If we respect default default build, and build request does not include 
<rtti>off, we'll be using link-incompatible properties for building "l".
Probably the solution is to say that default-build cannot change link
incompatible properties.

- Volodya