java 的 makefile
我不明白我的 makefile 做错了什么：
JAVA_SRCS:=$(wildcard tasks/src/*.java) JAVA_CLASSES=$(subst /src/,/build/,$(JAVA_SRCS:.java=.class)) JFLAGS=-cp jar/octobot.jar -d tasks/build JC=javac .SUFFIXES: .java .class .java.class: $(JC) $(JFLAGS) $*.java default: build build: $(JAVA_CLASSES) clean: $(RM) tasks/build/*.class
我收到了这个错误：
make: *** No rule to make target `tasks/build/ClickTask.class', needed by `classes'. Stop. zsh: exit 2 make
但奇怪的是，当我像这样重写规则 build 时：
build: $(JAVA_SRCS:.java=.class)
没有错误，规则已启动，但每次都会执行时间（而且不正确）
i don't understand what i did wrong with my makefile :
JAVA_SRCS:=$(wildcard tasks/src/*.java) JAVA_CLASSES=$(subst /src/,/build/,$(JAVA_SRCS:.java=.class)) JFLAGS=-cp jar/octobot.jar -d tasks/build JC=javac .SUFFIXES: .java .class .java.class: $(JC) $(JFLAGS) $*.java default: build build: $(JAVA_CLASSES) clean: $(RM) tasks/build/*.class
I got this error :
make: *** No rule to make target `tasks/build/ClickTask.class', needed by `classes'. Stop. zsh: exit 2 make
But strangely, when i re-write the rule build like this :
build: $(JAVA_SRCS:.java=.class)
no error, the rule is launched but does it every time (and it's not correct)
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评论（2）
@Dean Povey 是正确的：您不能使用后缀规则来执行此操作，因为它们与源在同一目录中查找。但是，您可以使用 GNU Make 模式规则来执行此操作（并且您已经在 Makefile 中使用了 GNUMake-isms，所以无论如何）：
但是请注意，
make不适合构建java 源代码作为一个.java文件可能会产生许多.class文件（例如内部类）。 Automake 解决这个问题的方法是在一次调用javac中编译所有内容，并写出一个时间戳文件（例如echo timestamp > classnoinst.stamp）。然后，任何需要构建的 java 源代码都依赖于该 stamp 文件，并且make clean会删除.stamp以及.class文件。@Dean Povey is correct: you can't do this with suffix rules, because they look in the same directory as the source. You can, however, do this with a GNU Make pattern rule (and you're already using GNUMake-isms in your Makefile, so whatever):
Note, however, that
makeis ill-suited to building java source as one.javafile can result in many.classfiles (inner classes, for instance). Automake's approach to this problem is to compile everything in a single call tojavacand write out a timestamp file (echo timestamp > classnoinst.stamp, for example). Then anything that needs the java sources built depends on that stamp file andmake cleanremoves the.stampalong with the.classfiles.我认为这是因为你的 src 位于不同的目录中。它正在寻找tasks/build/ClickTask.java，但您的源是tasks/src/ClickTask.java。
第二种情况之所以有效，是因为它找到了源文件，但随后期望类文件最终出现在tasks/src中，但它并没有因此一直重建。
对于如何使用 Makefile 执行此操作，我没有一个好的答案，我倾向于将类文件放在同一目录中。或者，考虑使用 Ant 或 Maven，它们更容易支持这一点。
编辑：我认为这应该告诉你你需要什么：http://www.makelinux.net/make3/make3-CHP-8-SECT-1.html
I think this is because your src is in a different directory. It is looking for tasks/build/ClickTask.java but your source is tasks/src/ClickTask.java.
The second case works because it finds the source file, but then expects the class file to end up in tasks/src, which it doesn't hence it rebuilds all the time.
I don't have a good answer for how to do this with Makefiles, I tend to just put class files in the same directory. Alternatively, think about using Ant or Maven which supports this much more easily.
EDIT: I think this should tell you what you need: http://www.makelinux.net/make3/make3-CHP-8-SECT-1.html