I had a similar problem, and was able to work around it by putting the include for the dependent files inside an ifdef, like this for your example:

-include include1
ifdef A
-include include2
endif

Haven't had time to check the code, but this apparently tricks make into thinking it has processed all the included makefiles after the first one, so it restarts itself, gets the value of A from include1, realizes it needs to process the code inside the ifdef, and subsequently includes include2. With this structure, there don't appear to be any cases in which A or B end up undefined.

Paul Smith explained to me on the help-make mailing list that this results from the way Make works: read all includes, rebuild all includes, restart make. So in effect the "previous version" of include1 is used when building include2, because Make is not restarted until ALL includes have been rebuilt.

That makes this bug a requested feature enhancement rather than an outright bug.

Here is my requested feature: Make should restart itself before invoking any rule that has a makefile as a preqrequisite and that makefile has already been rebuilt.

Any other means of making sure the "current version" of the rebuilt makefile gets used would also be acceptable.