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