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- # SPDX-License-Identifier: GPL-2.0
- # Shorthand
- warning = $(warning-if,y,$(1))
- # Simply expanded variable.
- X := 1
- SIMPLE := $(X)
- X := 2
- $(warning,SIMPLE = $(SIMPLE))
- # Recursively expanded variable.
- X := 1
- RECURSIVE = $(X)
- X := 2
- $(warning,RECURSIVE = $(RECURSIVE))
- # Append something to a simply expanded variable.
- Y := 3
- SIMPLE += $(Y)
- Y := 4
- $(warning,SIMPLE = $(SIMPLE))
- # Append something to a recursively expanded variable.
- Y := 3
- RECURSIVE += $(Y)
- Y := 4
- $(warning,RECURSIVE = $(RECURSIVE))
- # Use += operator to an undefined variable.
- # This works as a recursively expanded variable.
- Y := 3
- UNDEFINED_VARIABLE += $(Y)
- Y := 4
- $(warning,UNDEFINED_VARIABLE = $(UNDEFINED_VARIABLE))
- # You can use variable references for the lefthand side of assignment statement.
- X := A
- Y := B
- $(X)$(Y) := 5
- $(warning,AB = $(AB))
- # User-defined function.
- greeting = $(1), my name is $(2).
- $(warning,$(greeting,Hello,John))
- # The number of arguments is not checked for user-defined functions.
- # If some arguments are optional, it is useful to pass fewer parameters.
- # $(2) will be blank in this case.
- $(warning,$(greeting,Hello))
- # Unreferenced parameters are just ignored.
- $(warning,$(greeting,Hello,John,ignored,ignored))
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