| # 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)) |
