[Boost-build] How can I include and use Jambase rules to my bjam/b2 build?

Subject: [Boost-build] How can I include and use Jambase rules to my bjam/b2 build?
From: Dirk Bächle (tshortik_at_[hidden])
Date: 2018-10-01 05:49:46

Hi there,

at work I tried to build an old software package (Ingres DBMS 10.1) from 
source over the last two weeks. It contained Jamfile and Jamrules files 
in its tree structure, so I concluded that I would have to use bjam/b2 
to get things going. The project's documentation wasn't specific enough 
about this point as it turned out.

I had one major problem, the Jamfiles would use a lot of definitions 
from the "Jambase" file, like "SubDir" a.s.o. Everytime I started the 
build, I would get the error "unknown rule", as you can also see in the 
question that I posted on StackOverflow:

https://stackoverflow.com/questions/52515654/how-can-i-include-the-jambase-file-to-my-build

I finally decided to give an older Jam version a try, and voila: with 
ft-jam 2.5.2 the project compiles flawlessly without any further ado. Yay!

So, basically everything is fine now and I can use ft-jam for my 
purposes. But I still wonder whether I could also use bjam/b2 for the 
compile. What is the purpose of the internal Jambase definition ("+" 
file) and the "-f" option in bjam? Is it only for bootstrapping b2 
itself, or can I use it while running b2? If yes, how do I activate it? 
How does a MWE look in this case?

Feel free to answer my questions on SO directly. Otherwise I'll try to 
provide an explanation myself, based on the replies from this list.

Thanks a lot in advance for any clarifications and pointers to 
additional documentation.

Best regards,

Dirk