从命令行到环境的Makefile变量

Question

有没有办法检测是否已从环境设置变量而不是命令行？

我希望有人援引以作区分make LIB=mylib对make与被定义$ LIB.

Answer 1

是.您可以使用origin函数来确定变量的定义位置.

ifneq (,$(findstring environment,$(origin LIB)))
    # LIB was defined by the environment
else
    # LIB was defined some other way
endif