gnu make - Execution flow of Makefile which includes other makefile -

1) how makefile execution flow works, in case suppose makefile-1 includes makefile-2 , makefile-2 includes makefile-3 ?

2) in case if included makefiles contains rules , variables supposed used 3 - how works ? happens if 1 includes same makefile more once ?

3) use of export variables of included makefile ? - available in of there makefile,

what understanding, makefile interpreter(or don't know term suits better here) reads line in makefile, , if there include directive makes variable/rules available in makefile(top level make-which includes other).

4) happens if 2 included makefiles overrides variables or rule of each others ? last included makefile takes priority ?

5) if rule in included makefile calls rule of top level makefile, executes top level makefile entirely (starting first line) ?

6) there 2 kind of assignments in make:

i) expanded @ time of use (=)

ii) expanded @ time of declaration (:=) how kind of variables handles in multilevel makefiles ?

7) happens if use gnumake's functions notdir, patsubt when creates list

file = abc def ghi  file += $(notdir ghi/jkl) 

when notdir call happens ?

(and if use ':=' difference ?) 

consider make contains following rule, gets called @ time when dependency resolved ?

rule : file 

nothing special wrt ordering happens when makefile included. make, it's if constructed 1 big makefile contents of included makefile inserted include statement appears in parent makefile, passed 1 big makefile make.

so, rules overriding things (variables, etc.) identical if override variable in single makefile: each subsequent assignment of variable replaces value of previous assignment.

if define (single-colon) rule recipe target, again later, error message , make ignores 1 of them.

the first explicit target listed in makefile, included or not, default target.

etc.

remember make never "executes" makefile entirely. make not procedural language, shell script. first parses makefiles , constructs dependency graph internally. chooses default target or targets, , walks sections of graph starting each one.

edited:

if above doesn't answer other questions, think should experiment little bit. try , see happens! it's easier asking explain it, plus you'll understand better if figure out yourself.