如何在GNU Make中正确注释变量定义？ [英] How do I properly comment a variable definition in GNU Make?

问题描述

所以我想在线注释Makefile中的变量定义。问题是Make不会在定义及其注释之间去除空格。这是我的意思的示例：

So I want to comment variable definitions in Makefile in-line. The problem is that Make doesn't strip white spaces between the definition and its comment. Here is an example of what I mean:

OPTS += -DBLA       # Does bla
OPTS += -DBLUBB     # Does blubb
OPTS += -DEND

.PHONY test
test:
    @echo $(OPTS)

输出

-DBLA       -DBLUBB     -DEND

在选项之间有多余的空格。我想要的是这样：

with annoying extra white spaces between the options. What I want is this:

-DBLA -DBLUBB -DEND

如何解决此问题？ Make字符串函数 @echo $（strip $（OPTS））仅会删除 -DEND 之后或 -DBLA ，而不是两者之间。到目前为止，我的肮脏技巧是 @echo $（shell $（OPTS）），该方法会删除不需要的空间，但使用shell调用会这样做，这可能会带来其他问题，即通过 $（OPTS）变量进行不必要的外壳注入。有更好的方法吗？简单的 @echo（$ subst ...）在混合空格上不起作用，除非一个空格全部替换掉​​然后在-中重新插入code>。

How do I get around this Problem? The Make string function @echo $(strip $(OPTS)) would only strip whitespaces after -DEND or before -DBLA, not inbetween. My dirty hack so far is @echo $(shell $(OPTS)), which strips the unwanted spaces but uses a shell call to do so, that probably will introduce other problems, i.e. unwanted shell injection via the $(OPTS) variable. Is there a better way to do it? Simple @echo ($subst ...) doesn't work on mixed whitespaces unless one replaces all of them an then reinserts at the -.

推荐答案

当然，'zZz'可以替换为任何不可能的匹配项...

Of course, 'zZz' could be replaced with any "impossible" match...

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