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makefileeval

Are evals concurrently safe across targets?

I'm wondering if there are any potential race conditions when using evals across targets. So for example, if I have:

all1:
    $(eval X:=1)
    $(eval Y:=1)
    @echo "[$@] X: $(X), Y: $(Y)"

all2:
    $(eval Y:=2);
    $(eval X:=2);
    @echo "[$@] X: $(X), Y: $(Y)"

and then ran 

 make all all2 -j

Are X and Y guaranteed to be the same values for the same target, or can one instance of the target expansion potentially scribble on the other as it's expanding?

(Background -- I'm debugging an inconsistent make bug on some makefiles which use evals to set some common variables across many targets, and I'm wondering if this could be a contributing factor)

Solution

  • make -j runs each job in a separate process. Variable changes don't transfer between make processes.