Is there a way to detect whether a variable has been set from the environment vs. on the command line?
I would like to distinguish between someone invoking make with make LIB=mylib
vs. make
and $LIB being defined.
Yes. You can use the origin function to determine where a variable was defined.
ifneq (,$(findstring environment,$(origin LIB))) # LIB was defined by the environment else # LIB was defined some other way endif
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