On Thu, 2020-07-02 at 17:16 +0200, Jan Beulich wrote: > > export wom > > introduces the variable to the env and set origin to environment. > > Not according to my observations.
The difference is whether the variable already exists in the environment or not. For this makefile: export FOO $(info FOO: $(origin FOO)) all:; If you run it like this: $ FOO= make FOO: environment make: 'all' is up to date. But if you run it like this: $ unset FOO; make FOO: file make: 'all' is up to date. Basically, if you run "export FOO" and FOO does not currently exist at all, either in the environment or in the makefile, then it's created in make and assigned a "file" origin. I'm not sure how it could be otherwise: by specifying "export" you ARE creating that variable, because it will be placed into the child's environment when a recipe is invoked, even if it's not set. In other words, if FOO is not already a variable make knows about then running "export FOO" makes it into a variable that make knows about, which has its "export" flag set. For example if you change the above makefile: export FOO $(info FOO: $(origin FOO)) all: ; @env | grep FOO then you run: $ unset FOO; make FOO: file FOO= make: 'all' is up to date. you can see that "FOO" is in the environment in the recipe even though it wasn't in the environment when make started.
