Re: problem with target-specific vars and dependencies

[Boris Kolpackov]

Tzafrir Cohen <address@hidden> writes:

> My makefile:
> 
> c: var=1
> 
> c: b
>       @echo making $@ from $^, var=$(var)
> 
> b: a
>       @echo making $@ from $^, var=$(var)
> 
> a:
> 
> 
> $ make b c
> making b from a, var=
> making c from b, var=1
> $ make c
> making b from a, var=1
> making c from b, var=1
> 
> Shouldn't 'make b' get the value of 'var' fom the target-specific 
> assignment of c?

Yes, if it's built because `c' depends on it (as is the case in your
second invocation). In other words, target-specific variable inheritance
is a dynamic process which takes into account the dependency path that
lead to rebuilt of the target.

IMO, target-specific variable inheritance is quite useless feature
exactly because of this. Also consider something along these lines:

all: a b

a: var := a
b: var := b

a: c
b: c

c:
        echo $(var)


When you run make with job server (e.g., make -j 2) there is no way to
predict the output of this makefile. In fact it could be different in
two consequent invocations.


-boris