用于切换 Makefile 中目标的先决条件的变量

Question

我希望使用“MY_TYPE”来切换目标“top”的先决条件。

基于 MY_TYPE 我可以选择所需的先决条件

例如，对于

MY_TYPE=FOO ，我希望 $(BUILD) $(TARGETS) $(X_LOCALS) 作为 top 的先决条件

MY_TYPE=BAR，我希望 $(BUILD) $(TARGETS) $(Y_LOCALS) 作为 top 的先决条件

我怎样才能实现它？

下面是一个简单的代码sn-p。

BUILD = build
TARGETS = targets
XLOCALS = xlocals
YLOCALS = ylocals

# can be FOO or BAR
MY_TYPE ?= FOO

$(BUILD):
    printf "\t Doing Build\n"

$(TARGETS): 
    printf "\t Doing target\n"

$(XLOCALS):
    printf "\t my local build for X \n"

$(YLOCALS):
    printf "\t my local build for Y \n"


# based on MY_TYPE Can I select the pre-requisites required
# For example, for 
# MY_TYPE=FOO , I wish to have  $(BUILD) $(TARGETS) $(X_LOCALS) as pre-requisites for 'top' target
# MY_TYPE=BAR , I wish to have  $(BUILD) $(TARGETS) $(Y_LOCALS) as pre-requisites for 'top' target
# How can I achieve it .

top: $(BUILD) $(TARGETS) $(XLOCALS)
    printf "\t doing top\n"

很高兴听取您的意见。

Answer 1

没有什么比这更简单的了，只需使用conditionals：

ifeq ($(MY_TYPE),FOO)
top: $(X_LOCALS)
endif

ifeq ($(MY_TYPE),BAR)
top: $(Y_LOCALS)
endif

top: $(BUILD) $(TARGETS)
        @echo prereqs are $^