使用cmake跨不同目录的项目依赖项 [英] Project dependencies across different directories with cmake

问题描述

假设我有这样的项目结构：

Suppose I have such project structure:

Root
  + ProjA
     + SubA.1
     + SubA.2
  + ProjB
     + SubB.1
     + SubB.2

我设置的依赖项是：

SubA.2 depends on SubA.1
ProjA depends on SubA.1 and SubA.2 
ProjB depends on ProjA

使以 make -jX 开头的构建顺序如下所示：

I want to make the build order looks like this when start with make -jX:

1. SubA.1
2. SubA.2
3. SubB.1 SubB.2

但是事实是：

1. SubA.1 SubB.1 SubB.2
2. SubA.2

ProjB =>在 SubA 之后，不能使用ProjA 来构建所有 SubB 。

It seems the ProjB => ProjA can't be used to make all the SubBs build after SubAs.

在所有 SubA SubB

How can I make all the SubBs build after all the SubAs finishes?

推荐答案

在CMake中，依赖关系只能按目标设置。

In CMake dependencies can be set only on per-target basis.

您应该确定 ProjB 是否取决于 ProjA 内部 c $ c>与否。 内部是指目标名称，CMake变量的值等等。

You should decide, whether ProjB depends on internals of ProjA or not. By "internals" I mean names of targets, values of CMake variables and so on.

1. 如果 ProjB 实际上需要 ProjA 的内部组件，您可以仔细确定 ProjA 的目标或 ProjB 的另一个目标，并仅设置所需的依赖项。这样构建 ProjA 可能会与 ProjB 和 make -j ，但构建是正确的。



1. If ProjB actually require internals of ProjA, you may carefully determine targets of ProjA, which are required for one or another target of ProjB, and set only needed dependencies. Such a way building of ProjA may interleave with ProjB with make -j, but building will be correct.

例如，如果 SubB.1 是可执行文件，需要 SubA.1 库进行链接，然后

E.g., if SubB.1 is executable, which requires SubA.1 library for link with, then

target_link_libraries(SubB.1 SubA.1)

自动设置所需的依赖项。

automatically sets needed dependencies.

如果使用可执行文件 SubA.2 生成了 SubB.2 ，则用法

If SubB.2 is generated using executable SubA.2, then usage

add_custom_command(OUTPUT <subB.2_file>
    COMMAND SubA.2 <args>
)

将自动设置所需的依赖项。

will automatically set needed dependencies.

1. 如果 ProjB 不知道 ProjA 的内部，并且只有在已经构建 ProjA 的情况下才能构建 ProjB ，然后您可以使用 ExternalProject_Add 用于构建两个项目并设置已创建目标之间的依赖关系：

1. If ProjB doesn't aware about internal of ProjA and it is only known that ProjB can be built only when ProjA is already built, then you may use ExternalProject_Add for build both projects and set dependencies between created targets:

CMakeLists.txt ：

ExternalProject_Add(ProjA ...)
ExternalProject_Add(ProjB ...)
# Now `ProjA` and `ProjB` are targets in top-level project.
add_dependencies(ProjB ProjA)

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