Makefile

Assignment Operators

Lazy Set

VARIABLE = value

• VARIABLE is recursively expanded whenever it is used

Immediate Set

VARIABLE:= value

• VARIABLE is expanded once at declaration

Lazy Set if Absent

VARIABLE?= value

• Setting of a variable only if it doesn’t ahve a value
• value is always evaluated as follows:

ifeq($(origin VARIABLE), undefined)
 VARIABLE = value
endif

Append

VARIABLE += value

• Appending the supplied value to theexisting value (or setting to that value if the variable didn’t exist)