更改make变量，并从同一Makefile中的配方调用另一个规则？


Change a make variable, and call another rule, from a recipe in same Makefile?

我已经看到了如何从make目标手动调用另一个目标了？，但我的问题有点不同；请考虑这个示例(注意，stackoverflow.com将选项卡更改为显示中的空格；但如果尝试编辑，则选项卡保留在源中)：

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TEXENGINE=pdflatex

pdflatex:
    echo the engine is $(TEXENGINE)

lualatex:
    TEXENGINE=lualatex
    echo Here I want to call the pdflatex rule, to check $(TEXENGINE) there!

在这里，如果我运行缺省目标(pdflatex，我得到预期的输出：

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$ make pdflatex
echo the engine is pdflatex
the engine is pdflatex

但是，对于目标lualatex，我想：

  • 将make变量TEXENGINE改为lualatex，然后
  • 调用与pdflatex中相同的代码(使用它)。

我怎么能做到？

很明显，在我的lualatex规则中，我甚至没有设法改变TEXENGINE变量，因为我在尝试它时会得到：

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$ make lualatex
TEXENGINE=lualatex
echo Here I want to call the pdflatex rule, to check pdflatex there!
Here I want to call the pdflatex rule, to check pdflatex there!

…所以我真的想知道makefiles中是否有这样的功能。

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使用目标特定变量

There is one more special feature of target-specific variables: when you define a target-specific variable that variable value is also in effect for all prerequisites of this target, and all their prerequisites, etc. (unless those prerequisites override that variable with their own target-specific variable value).

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TEXENGINE=pdflatex

pdflatex:
    echo the engine is $(TEXENGINE)

lualatex: TEXENGINE=lualatex
lualatex: pdflatex
    echo Here I want to call the pdflatex rule, to check $(TEXENGINE) there!

输出是：

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$ make pdflatex
echo the engine is pdflatex
the engine is pdflatex
$ make lualatex
echo the engine is lualatex
the engine is lualatex
echo Here I want to call the pdflatex rule, to check lualatex there!
Here I want to call the pdflatex rule, to check lualatex there!
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嗯，我设法找到了一种解决办法，但我不太明白，所以我会感激一个更有学问的答案。对于我来说，这些链接有助于：

  • 从规则内设置变量
  • make:规则调用规则
  • 从命令行传递附加变量

下面是修改过的示例——显然，为了在以后从规则调用规则(不是作为先决条件，而是作为后决条件)，我只能递归调用make，同时在命令行上指定新的变量值：

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TEXENGINE=pdflatex

pdflatex:
    echo the engine is $(TEXENGINE)

lualatex:
    echo Here I want to call the pdflatex rule, to check $(TEXENGINE) there!
    $(MAKE) TEXENGINE=lualatex pdflatex

输出比我想要的要详细一些，但是它可以工作：

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$ make lualatex
echo Here I want to call the pdflatex rule, to check pdflatex there!
Here I want to call the pdflatex rule, to check pdflatex there!
make TEXENGINE=lualatex pdflatex
make[1]: Entering directory `/tmp'
echo the engine is lualatex
the engine is lualatex
make[1]: Leaving directory `/tmp'

…这完全是我想要的命令行交互方式，但我知道这不是最好的解决方案(参见下面的@jonathanwakely的评论)

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