Makefile生成器创建两个文件 [英] Makefile generator creates two files

问题描述

我有一个生成器程序，可以创建两个版本文件，例如ver.h和ver.cpp.我最终的构建目标取决于这两个文件，而构建这两个文件的规则是一个程序.如果我这样做:

I have a generator program that creates two version files, say ver.h and ver.cpp. My ultimate build target depends on both of these files, and the rule for building both is that one program. If I did this:

build : ver.h ver.cpp

ver.h ver.cpp :
    ./gen/version/program

然后并行构建可以运行program两次，这虽然不是 bad ，但这只是多余的.我想我可以让它们都依赖于伪造的目标:

then a parallel build could run program twice, which, while not bad is just excessive. I figure I could have them both depend on a phony target:

ver.h ver.cpp : do-version-impl

do-version-impl:
    ./gen/version/program

.PHONY : do-version-impl

这是最好的方法吗?必须引入一个假音规则来做到这一点，这听起来有点可笑.

Is that the best way to do this? It smells a little funny to have to introduce a phony rule to do this.

推荐答案

将假目标作为前提是一个坏主意.即使存在ver.*文件，也会运行program，这是一个误报错误.

Using the phony target as the prerequisite is a bad idea. program will be run even if ver.* files exist, which is a false positive error.

更妙的是，仅当GNU Make文件是配方规则的目标时，才保证更新其文件时间戳.因此，即使program始终运行，反过来依赖于ver.*文件的所有内容也可能根本无法更新！

More subtly, GNU Make is only guaranteed to update its file timestamp, if that file is a target of a rule with a recipe. So here, even though program is always run, anything that in turn depends on ver.* files might not get updated at all!

我认为最好不要为每个目标组成不自然的模式，而要明确:

In my opinion it is best to not make up unnatural patterns for each target, but instead, go explicit:

您正在生成一个主"文件，即ver.cpp.将"no-op"食谱;用于另一个食谱，可以像这样将其放在同一行上:

There is a "main" file that you are generating, that is ver.cpp. Use the "no-op" recipe ; for the other one, which can be put on the same line like this:

ver.h: ver.cpp ;
ver.cpp: Makefile
    ./gen/version/program

此方法从您编写的内容开始，但添加了非常重要的;.

This method starts with what you wrote, but adds the very important ;.

如果您没有主"文件的自然候选人，那么我认为最好使用前哨":

If you did not have a natural candidate for the "main" file, then in my opinion it is best to use a "sentinel":

ver.h ver.cpp: sentinel ;

sentinel: Makefile
    ./gen/version/program
    touch $@

同样，此方法与您的方法之一相似，但非常重要的是，它不使用假音，而是使用真实文件.

Again, this method is similar to one of your methods, but very importantly, does not use a phony, but a real file.

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