Makefile更新库依赖 [英] Makefile updated library dependency

问题描述

我有一个大的makefile来构建几个库，安装它们，然后继续构建与这些已安装的库链接的对象。我的麻烦是，我想使用-lfoo -lbar作为g ++标志来链接两个已安装的库，但依赖关系被弄乱了。如果我更改图书馆foo所依赖的标题42.h，那么当然make将重建并安装它，但是它确实不似乎注意到我的对象marvin使用了 - lfoo和marvin与旧版本保持联系...：（

到目前为止，我一直在做：

$ $ $ $ $ $（$）$（$）$（$）$（$）$（$） ）-o $ @ $ ^ $（LINKFLAGS）$（LINKLIBS）

但是我在点，这不再是一个可行的选择，我需要简单地将库-lfoo -lbar添加到LINKFLAGS变量中，并使链接器显示出来。

平均而言，我已经别的几个命令来明确地吹走有问题的对象文件，然后调用make，但是这是愚蠢的，我按下了时间，但如果需要，我可以发布一个小例子也许是星期五晚上或星期六上午。

因此，我觉得我是回到一些坏版本的Windows dll地狱。有没有什么可以做的，使链接器注意到一个对象被创建的库的版本，如果这些库改变了它，并重新链接它。

更新：所以，直到现在，我还没有机会把建议摔倒。我正在做的是使用静态库的缺点。所以我不能使用 ldd 。所以我重写了我的Makefile并找到了解决这个问题的方法。如果我有时间，我会发布我做的。

解决方案

据我所知，一般来说非常好地自动检测这样的依赖关系。 （这不是真正的工作; make是一个更高级别的工具，不知道它产生的命令的具体细节或这些命令的作用。）

两个选项请记住。

首先，您可以在$（myObject）上运行 ldd ，将库列表保存到一个文本文件，然后将其作为依赖关系的列表反馈到您的makefile中。 （这是类似于使用-MD将头文件列表保存到文本文件，然后将其作为源文件编译的附加规则提供给makefile，如Sam Miller所建议的。）

其次，您可以使用LINKLIBS变量，并使用GNU Make的函数让相同的变量适用于依赖关系和命令行选项。例如：

  LINKLIBS：= /explicit/path/to/lib/libfoo.so 
 $（myObject） ：$（localSrc）$（LINKLIBS）
 $（CXX）$（CPPFLAGS）$（INCFLAGS）-o $ @ $ ^ $（LINKFLAGS）$（patsubst％， -  l：％，$（LINKLIBS）） 
  

I have a large makefile which builds several libraries, installs them, and then keeps on building objects which link against those installed libraries. My trouble is that I want to use "-lfoo -lbar" as g++ flags to link against the two installed libraries, but the dependencies get messed up. If I change a header "42.h" which the library foo depends on, then of course make will rebuild and install it, but it does not appear to notice that my object "marvin" used "-lfoo" and marvin is left linked against the old version... :(

Thus far, I've been doing:

$(myObject): $(localSrc) /explicit/path/to/lib/libfoo.a
            $(CXX) $(CPPFLAGS) $(INCFLAGS) -o $@ $^ $(LINKFLAGS) $(LINKLIBS)

But I'm at a point where this is no longer a viable option. I need to simply add libraries "-lfoo -lbar" to the LINKFLAGS variable and have the linker figure things out?

In the mean time, I've aliased a few commands to explicitly blow away the object file(s) in question and then call make, but this is getting silly. I'm pressed for time, but if necessary I could post a small example perhaps Friday evening or Saturday morning.

Hence, I feel like I'm back in some bad version of windows dll hell. Is there something I can do to make the linker take notice of the version of the libraries that an object was built against and relink it if those libraries change??

Updated: So I hadn't had a chance to crash the suggestions until now. The drawback of what I'm doing is using static libraries. So I can't use ldd. So I rewrote my Makefile and found a way around this problem. If I get time, I'll post what I did.

解决方案

As far as I know, make in general isn't very good at automatically detecting dependencies like this. (It's not really make's job; make is a higher-level tool that's not aware of the specifics of the commands that it's spawning or what those commands do.)

Two options come to mind.

First, you could run ldd on $(myObject), save its list of libraries to a text file, then feed that back into your makefile as a list of dependencies. (This is similar to using -MD to save a list of header files to a text file then feeding that back into the makefile as additional rules for source file compilation, as Sam Miller suggested.)

Second, you could use a LINKLIBS variable as you've been using, and use GNU Make's functions to let the same variable work for both dependencies and command-line options. For example:

LINKLIBS := /explicit/path/to/lib/libfoo.so
$(myObject): $(localSrc) $(LINKLIBS)
        $(CXX) $(CPPFLAGS) $(INCFLAGS) -o $@ $^ $(LINKFLAGS) $(patsubst %,-l:%,$(LINKLIBS))

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