使用cmake，如何将由external_project语句构建的对象文件链接到另一个库？ [英] Using cmake, how to link an object file built by an external_project statement into another library?

问题描述

在我们的项目中，我们想要使用第三方库（A），它使用自动工具构建，并生成一个对象文件（B），我们需要一个我们的库（C）的@链接时间。 p>

  external_project（
 A 
 ... 
）
 set_source_files_properties A）
 add_library（C ... A）
 add_dependency（CB）
  

我有一个印象，这应该做的伎俩，但cmake命令失败，说明它在检查add_library期间找不到文件A.

任何修复或替代解决方案将非常感谢！ （更改第三方库不是一个选项）
感谢！

解决方案

这里有几个问题：

• external_project 应为 ExternalProject_Add


• 源文件没有名为 DEPEND 的属性可用 - set_source_files_properties 命令在此无效。 （以下是源文件上的属性） / li>
  
• add_library 期望传递源文件列表，而不是另一个CMake目标（ A ）


• add_dependency 应为 add_dependencies

除了那些4行，它是OK： - ）

所以问题是你想包括对象文件 B在 add_library 调用中的，但是它不会在configure-time（当CMake被调用时） p>

我想你将要做如下事情：

  ExternalProject_Add（
 A 
 ... 
）
 
 set_source_files_properties（
 $ {B} PROPERTIES 
 EXTERNAL_OBJECT TRUE＃标识为对象文件
 GENERATED TRUE＃在配置时不需要文件存在
）
 
 add_library（C ... $ {B}）
  

In our project, we want to use a third-party library (A) which is built using autotools and which generates an object file (B) which we need @ link time of one of our libraries (C).

external_project(
    A
    ...
)
set_source_files_properties(B PROPERTIES DEPEND A)
add_library(C ... A)
add_dependency(C B)

I had the impression that this should do the trick, but the cmake command fails by stating that it cannot find file A during the check for add_library.

Any fixes or alternative solutions would be greatly appreciated! (changing the third-party library is not an option) thanks!

解决方案

There are a few issues here:

• external_project should be ExternalProject_Add
• Source files have no property called DEPEND available - the set_source_files_properties command has no effect here. (Here are the properties available on source files)
• add_library expects a list of source files to be passed, not another CMake target (which A is)
• add_dependency should be add_dependencies

Apart from those 4 lines it's all OK :-)

So the issue is going to be that you want to include the object file B in the add_library call, but it's not going to be available at configure-time (when CMake is invoked), only at build time.

I think you're going to have to do something like:

ExternalProject_Add(
    A
    ...
)

set_source_files_properties(
    ${B} PROPERTIES
    EXTERNAL_OBJECT TRUE  # Identifies this as an object file
    GENERATED TRUE  # Avoids need for file to exist at configure-time
)

add_library(C ... ${B})

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