RabbitMQ集群w / .Net客户端(RabbitMQ cluster w/ .Net client)

 这里有很多事要讨论。 首先，关于特定于目标的变量如何工作的心智模型并不十分准确（“一旦发现a.so应该构建”，“a.so：current = a.so就会被触发”）。 真正发生的是每个目标进行遭遇会创建一个新的“范围”，该范围在该目标及其所有先决条件被创建时处于活动状态，并且该目标的特定于目标的变量在该范围内有效。 一旦该范围退出（目标完成），那些变量设置就消失了。 
 
 在上面的示例中， 只有在创建bo作为a.so的先决条件时， a.so 才会在bo的配方中具有值a.so 如果创建bo作为b.so的先决条件，那么current将是b.so 因为你的makefile首先列出了a.so首先会构建它，因为bo只会被构建一次（每次调用make），它可能看起来总是使用a.so作为current的值，但这并不准确。 考虑一下： 
 
$ make all
Current .so is a.so
touch b.o
Current .so is a.so
touch a.so
Current .so is b.so
touch b.so
 
 但是这个： 
 
$ rm -f b.o
$ make b.so
Current .so is b.so
touch b.o
Current .so is b.so
touch b.so
 
 看看current如何设置b.so如果bo是构建的，因为它是b的先决条件而不是a.so 
 
 还有这个： 
 
$ rm -f b.o
$ make b.o
Current .so is
touch b.o
 
 这里因为bo不是任何.so的先决条件，所以根本没有设置current ！ 
 
 接下来要考虑的是这一行： 
 
%.so : current = $@
 
 这条线被bo “触发”并不是真的。 但是，这会将特定于模式的变量设置为值$@ （注意， 不要扩展$@变量！）。 这意味着每次扩展$(current) ，它将扩展为$@ ，这是当前目标名称，无论其使用的是什么配方。因此除非当前目标，否则不会扩展到a.so或b.so name实际上是a.so或b.so 如果目标名称是bo则$@扩展为bo 。 
 
 如果你想这样做你不能使用像$@这样的变量，你必须使用实际值。 您可以使用eval执行此操作，例如： 
 
sofiles = a b
$(foreach SO,$(sofiles),$(eval $(SO).so: current = $(SO).so))
 
 但是，基于上面的第一条评论，我不确定这是否足以满足您的需求。 

There are many things to discuss here. First, your mental model of how target-specific variables works is not quite accurate ("the line a.so: current = a.so gets triggered as soon as make finds out that a.so should be build"). What really happens is that each target make encounters creates a new "scope" which is active while that target and all its prerequisites are being created, and the target-specific variables for that target are in effect inside that scope. Once that scope exits (the target is finished) then those variable settings are gone.
 
In your example above, current will have the value a.so inside the recipe for b.o only when b.o is being created as a prerequisite of a.so. If b.o was being created as a prerequisite of b.so, then current would be b.so. Because your makefile lists a.so first it will be built first, and because b.o will only be built once (per invocation of make), it may appear that it's always using a.so as the value of current but that's not precisely accurate. Consider this:
 
$ make all
Current .so is a.so
touch b.o
Current .so is a.so
touch a.so
Current .so is b.so
touch b.so
 
But also this:
 
$ rm -f b.o
$ make b.so
Current .so is b.so
touch b.o
Current .so is b.so
touch b.so
 
See how current is set to b.so if b.o is built because it's a prerequisite of b.so not a.so.
 
And also this:
 
$ rm -f b.o
$ make b.o
Current .so is
touch b.o
 
Here because b.o isn't a prerequisite of any .so, then current is not set at all!
 
The next thing to think about is this line:
 
%.so : current = $@
 
It's not true that this line is "triggered" for b.o. However, this sets the pattern-specific variable current to the value $@ (note, NOT to the expansion of the $@ variable!). This means that each time $(current) is expanded it will expand to $@, which is the current target name, for whatever recipe it's used in. So this won't expand to a.so or b.so unless the current target name is actually a.so or b.so. If the target name is b.o then $@ expands to b.o.
 
If you want to do this you can't use a variable like $@, you have to use the real value. You can do this with eval, for example:
 
sofiles = a b
$(foreach SO,$(sofiles),$(eval $(SO).so: current = $(SO).so))
 
However, based on the first comments above I'm not sure that's sufficient for your needs.