制造:取决于目标的可变需求 [英] Make: variable requirements that depend on the target

问题描述

我有一个Makefile，看起来像这样:

I have a Makefile that looks roughly like this:

default: en

.PHONY: default en es

en: NUMBER=number
es: NUMBER=numero

TARGET=$(NUMBER)-word
INTERMEDIATE=$(NUMBER)-tmp

en: number
es: number

number: $(INTERMEDIATE)
  touch $(TARGET)

$(INTERMEDIATE):
  @echo Please provide file $(INTERMEDIATE)
  @exit 1

clean:
  rm *-word *-tmp

要使用它，请致电make en(也是默认值)或make es.如我所见，此Makefile具有两个主要功能:

To use it, you'd call make en (also a default) or make es. As I see it, this Makefile has two main features:

• 用户必须提前提供中间要求($(INTERMEDIATE)).
• 此要求是一个变量，其值取决于目标.

运行此命令时，我得到以下信息:

When I run this, I get the following:

$ make
Please provide file number-tmp
make: *** [-tmp] Error 1

这个错误告诉我，对于我想要的变量来说，解决变量的时间太晚了.失败的规则为-tmp，表示在确定要运行的规则时无法告诉$(NUMBER)的值.但是，它会在运行规则时得到解决.

This error suggests to me that variables are resolved one stage too late for what I intend. The failing rule is -tmp, implying it can't tell the value of $(NUMBER) when deciding what rules to run. However it's resolved by the time it's running the rule.

那我怎么做呢?

推荐答案

文档明确指出，您不能在目标或先决条件内使用特定于目标的变量值:

The documentation is clear that you cannot use target-specific variable values inside targets or prerequisites:

另一个例外是特定于目标的变量值.此功能使您可以根据make当前正在构建的目标为同一变量定义不同的值. 与自动变量一样，这些值仅在目标配方的上下文中(以及在其他特定于目标的分配中)可用.

您可以通过多种方式处理此问题.最简单的方法是将选择更改为使用变量而不是目标，然后使用构造的宏名称.假设您将值存储在LV变量中(您不应该使用LANG等，因为这对shell来说是特殊的)，如下所示:

There are multiple ways you could handle this. The simplest would be to change the selection to using a variable instead of a target, and use constructed macro names. Suppose you stored the value in the LV variable (you should not use LANG etc. because this is special to the shell), like this:

# Must be set on the command line
LV =

en_NUMBER := number
es_NUMBER := numero

TARGET := $($(LV)_NUMBER)-word
INTERMEDIATE := $($(LV)_NUMBER)-tmp

ifeq ($(TARGET),-word)
  $(error Missing/invalid LV value: '$(LV)')
endif

number: $(INTERMEDIATE)
        touch $(TARGET)

clean:
        rm *-word *-tmp

如果运行make LV=en，将得到number-word.如果运行make LV=es，将得到numero-word.如果运行make(无设置)或make LV=foo(无效设置)，则会出现错误.

If you run make LV=en you'll get number-word. If you run make LV=es you'll get numero-word. If you run make (no setting) or make LV=foo (invalid setting) you'll get an error.

还有其他方法可以做到这一点，但是如果您对您想要的内容没有完全的了解，我们就无法确定.

There are other ways to do this but without a complete understanding of what you want we can't say for sure.

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