makefile - 更改一个make变量，并从同一Makefile中的配方调用另一个规则？

Question

我已经看过How to manually call another target from a make target?，但是我的问题有点不同。考虑以下示例(请注意，stackoverflow.com将选项卡更改为显示中的空格；但是，如果您尝试编辑，则选项卡将保留在源代码中):

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，如果运行默认目标( pdflatex)，则会得到预期的输出:

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

但是，使用目标 lualatex，我想要:

将make变量TEXENGINE更改为lualatex，然后将

更改为

调用与pdflatex(使用它)相同的代码。

我该怎么办？

显然，在我的 lualatex规则中，我什至没有设法更改 TEXENGINE变量，因为尝试时会得到以下信息:

$ 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!

...所以我真的很想知道在Makefiles中是否可以进行这样的操作。

Answer 1

使用target-specific variable

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).

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!

输出为:

$ 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!