On 9 Jun 2009, at 20:08, Zachary Turner wrote:
That being said, compilation of boost itself isn't even the real use case, since a user of boost typically just compiles it once and is done. The real use case is for people using boost in their own projects, i.e. including lots of boost header files at various locations in their program. In this case, it has potential to make a huge impact, since developers frequently build code tens of times per day. Even the slightest change to a header file and a rebuild of the project to test the change has the potential to trigger a rebuild of numerous other files, so there's no reason not to take every measure possible to reduce compilation time.
While it would be a bit of work, I'd be very interested in seeing convincing numbers to this effect: If you add #pragma once (with suitable guards) to boost (or a substantial section of it), then prove that the resulting code produces speed improvements, then you would convince people! One thing to watch out for, in case you don't notice in advance: Some headers should NOT have #pragma once. Not very many, but such files exist. You'll probably want to try to find some way of guessing if a file already has a standard include guard (shouldn't be too hard to detect), and only #pragma once such files.
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost