54 lines
1.2 KiB
Plaintext
54 lines
1.2 KiB
Plaintext
|
# 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))
|