Ask:
What is the difference between :
VARIABLE = value
VARIABLE ?= value
VARIABLE := value
VARIABLE += value
I have read the section in GNU Make's manual, but it still doesn't make sense to me.
Explanation:
VARIABLE = value
Normal setting of a variable - values within it are recursively expanded when the variable is used, not when it's declared
VARIABLE := value
Setting of a variable with simple expansion of the values inside - values within it are expanded at declaration time.
VARIABLE ?= value
Setting of a variable only if it doesn't have a value
VARIABLE += value
Appending the supplied value to the existing value
