我怎么能中止一个make/makefile执行基于一个makefile的变量没有被设置/值?
我想出了这个，但只有在调用者没有显式运行目标(即只运行make)时才有效。
ifeq ($(MY_FLAG),)
abort: ## This MUST be the first target :( ugly
@echo Variable MY_FLAG not set && false
endif
all:
@echo MY_FLAG=$(MY_FLAG)
我认为这样的东西会是一个好主意，但在make的手册中没有找到任何东西:
ifndef MY_FLAG
.ABORT
endif
当前回答
另一个选择:
MY_FLAG = $(error Please set this flag)
尝试在任何地方使用此变量都会导致错误，除非从命令行覆盖它。
要接受环境变量，使用?=:
MY_FLAG ?= $(error Please set this flag)
其他回答
使用shell错误处理未设置变量(注意双$):
$ cat Makefile
foo:
echo "something is set to $${something:?}"
$ make foo
echo "something is set to ${something:?}"
/bin/sh: something: parameter null or not set
make: *** [foo] Error 127
$ make foo something=x
echo "something is set to ${something:?}"
something is set to x
如果需要自定义错误消息，请将其添加在?:
$ cat Makefile
hello:
echo "hello $${name:?please tell me who you are via \$$name}"
$ make hello
echo "hello ${name:?please tell me who you are via \$name}"
/bin/sh: name: please tell me who you are via $name
make: *** [hello] Error 127
$ make hello name=jesus
echo "hello ${name:?please tell me who you are via \$name}"
hello jesus
你可以使用IF来测试:
check:
@[ "${var}" ] || ( echo ">> var is not set"; exit 1 )
结果:
$ make check
>> var is not set
Makefile:2: recipe for target 'check' failed
make: *** [check] Error 1
使用shell函数测试:
foo:
test $(something)
用法:
$ make foo
test
Makefile:2: recipe for target 'foo' failed
make: *** [foo] Error 1
$ make foo something=x
test x
另一个选择:
MY_FLAG = $(error Please set this flag)
尝试在任何地方使用此变量都会导致错误，除非从命令行覆盖它。
要接受环境变量，使用?=:
MY_FLAG ?= $(error Please set this flag)
为了简单和简洁:
$ cat Makefile
check-%:
@: $(if $(value $*),,$(error $* is undefined))
bar:| check-foo
echo "foo is $$foo"
输出:
$ make bar
Makefile:2: *** foo is undefined. Stop.
$ make bar foo="something"
echo "foo is $$foo"
foo is something
