Question

该设置是一个包含以下内容的Makefile（受答案https://stackoverflow.com/a/20714468/185475的启发）：

prerule: VALUE = Hello
prerule: 
    @echo "in prerule"
    @echo ${VALUE}

record: prerule
    @echo "in record"
    @echo ${VALUE}

我想在一个规则中定义一个变量，该变量用作其他规则（或实际一组规则）的先决条件。使用当前设置，将生成以下输出：

$ make record 
in prerule
Hello
in record

$

我想要的输出如下：

$ make record 
in prerule
Hello
in record
Hello
$

Answer 1

您可以添加：

$(eval VALUE := $(VALUE))

到prerule的配方，但是要注意，一旦执行VALUE配方，它将在全局设置prerule变量。不仅是针对record规则的上下文。

演示：

$ cat Makefile
prerule: VALUE = Hello
prerule: 
    @echo "VALUE = $(VALUE) in $@"
    $(eval VALUE := $(VALUE))

record: prerule
    @echo "VALUE = $(VALUE) in $@"

foobar: 
    @echo "VALUE = $(VALUE) in $@"
$ make foobar
VALUE =  in foobar
$ make foobar record
VALUE =  in foobar
VALUE = Hello in prerule
VALUE = Hello in record
$ make record foobar
VALUE = Hello in prerule
VALUE = Hello in foobar
VALUE = Hello in record

在一个构建规则中定义变量，并在其他构建规则中使用它

1 个答案: